Periodic Table.

What is a Periodic Table:

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Periodic table is an arrangement of Chemical Elements. This arrangement has been made on the basis of Atomic numbers of the elements. The periodic table starts from Hydrogen Gas. Hydrogen gas is an element which has atomic number=1, which means there is one proton in the nucleus of a Hydrogen atom. Periodic Table starts from Hydrogen and lasts till Oganesson (Og) which has an atomic number=118. It means there are 118 elements in the periodic table or there are 118 known elements so far. These 118 elements are arranged in a sequence based on their ascending atomic numbers , and are classified in 18 groups. These groups are shown in vertical column, as shown in the above table. The elements of each group have similar chemical and physical properties. The horizontal rows of the periodic table are called the Periods of the Periodic Table. Hydrogen is the first element of the first Period while Helium is the last element of the first Period, because the element (Lithium) which follows Helium has similar properties with that of Hydrogen, therefore Lithium has been placed in the group of Hydrogen, thus starting a new period in the periodic table.  Each period starts from the element of first group. Detail of these periods in as under;


  • First period starts from Hydrogen and ends at Helium (there are two elements in this period)
  • Second period starts from Lithium and ends at Neon (there are 8 elements in this period)
  • Third period starts from Sodium and ends at Argon (there are 8 elements in this period)
  • Fourth period starts from Potassium and ends at Argon (there are 18 elements in this period)
  • Fifth period starts from Rubidium and ends at Xenon (there are 18 elements in this period)
  • Sixth period starts from Cesium and ends at Radon (there are 32 elements in this period)
  • Seventh period starts from Francium and ends at Oganesson (there are 32 elements in this period)

It is therefore clarified that there are only 7 periods in the Periodic Table. In each period there are more than two elements. These elements are vertically grouped, and all of the elements of each group have similar chemical and physical properties.



As early mentioned in article that there are 18 groups in the Periodic Table and the members of each group has similar properties.

Properties of Group 1:

Hydrogen is placed in above of the group 1 in Periodic Table, while the rest of the elements (Lithium, Sodium, Potassium, Rubidium, Caesium, and Francium)  are called Alkali Metals. The properties of the elements of this group are quite similar. Following resemblances are found in the properties of these elements.

  • There is only electron in the last shell of all the elements of group 1. In each case, the outer electron feels a net pull of 1+ from the nucleus. The positive charge on the nucleus is cut down by the negativeness of the inner electrons.

The alkali metals have the following properties in common:

  1. they have low melting and boiling points compared to most other metals
  2. they are very soft and can be cut easily with a knife
  3. they have low densities (lithium, sodium and potassium will float on water)
  4. they react quickly with water, producing hydroxides and hydrogen gas
  5. their hydroxides and oxides dissolve in water to form alkaline solutions
  • With the exception of some lithium compounds, these elements all form compounds which we consider as being fully ionic. They are so weakly electronegative that we assume that the electron pair is pulled so far away towards the chlorine (or whatever) that ions are formed.


Properties of Group 2:

The group 2 is comprised of 6 elements which are called Alkaline Earth Metals. The names of these elements are Beryllium, Magnesium, Calcium, Strontium, Barium, Radium. The similar properties of these 6 elements are :

The elements have very similar properties: they are all shiny, silvery-white, somewhat  reactive  metals  at standard temperature and pressure. Structurally, they have in common an outer s- electron shell which is full; that is, this orbital contains its full complement of two electrons, which these elements readily lose to form cations with charge +2, and an oxidation state of +2.

All the discovered alkaline earth metals occur in nature. Experiments have been conducted to attempt the synthesis of element 120, the next potential member of the group, but they have all met with failure.

Properties of Group 3:

Group 3 of the Periodic table included only Scandium and Yttrium. This group, like other d-block groups, should contain four elements, but it is not agreed what elements belong in the group. Scandium (Sc) and yttrium (Y) are always included, but the other two spaces are usually occupied by lanthanum (La) and actinium (Ac), or by lutetium (Lu) and lawrencium (Lr); less frequently, it is considered the group should be expanded to 32 elements (with all the lanthanides and actinides included) or contracted to contain only scandium and yttrium. When the group is understood to contain all of the lanthanides, its trivial name is the rare-earth metals.

The group 3 elements occur naturally, scandium, yttrium, and either lanthanum or lutetium. Lanthanum continues the trend started by two lighter members in general chemical behavior, while lutetium behaves more similarly to yttrium. While the choice of lutetium would be in accordance with the trend for period 6 transition metals to behave more similarly to their upper periodic table neighbors, the choice of lanthanum is in accordance with the trends in the s-block, which the group 3 elements are chemically more similar to. They all are silvery-white metals under standard conditions. The fourth element, either actinium or lawrencium, has only radioactive isotopes. Actinium, which occurs only in trace amounts, continues the trend in chemical behavior for metals that form tripositive ions with a noble gasconfiguration; synthetic lawrencium is calculated and partially shown to be more similar to lutetium and yttrium. So far, no experiments have been conducted to synthesize any element that could be the next group 3 element. Unbiunium (Ubu), which could be considered a group 3 element if preceded by lanthanum and actinium, might be synthesized in the near future, it being only three spaces away from the current heaviest element known, oganesson.

Properties of Group 4:

Group 4 is a group of elements in the periodic table. It contains the elements  titanium  Ti),  zirconium (Zr), hafnium (Hf) and rutherfordium (Rf). This group lies in the d-block of the periodic table. The group itself has not acquired a trivial name; it belongs to the broader grouping of the transition metals.

The three Group 4 elements that occur naturally are titanium, zirconium and hafnium. The first three members of the group share similar properties; all three are hard refractory metalsunder standard conditions. However, the fourth element rutherfordium (Rf), has been synthesized in the laboratory; none of its isotopes have been found occurring in nature. All isotopes of rutherfordium are radioactive. So far, no experiments in a supercollider have been conducted to synthesize the next member of the group, unpenthexium (Uph, element 156), and it is unlikely that they will be synthesized in the near future.

Properties of Group 5:

Group 5 (by IUPAC style) is a group of elements in the periodic table. Group 5 contains  vanadium  (V), niobium (Nb), tantalum (Ta) and dubnium (Db). This group lies in the d-blockof the periodic table. The group itself has not acquired a trivial name; it belongs to the broader grouping of the  transition metals.

The lighter three Group 5 elements occur naturally and share similar properties; all three are hard refractory metals under standard conditions. The fourth element, dubnium, has been synthesized in laboratories, but it has not been found occurring in nature, with half-life of the most stable isotope, dubnium-268, being only 29 hours, and other isotopes even more radioactive. To date, no experiments in a supercollider have been conducted to synthesize the next member of the group, either unpentpentium (Upp) or unpentseptium (Ups). As unpentpentium and unpentseptium are both late period 8 elements it is unlikely that these elements will be synthesized in the near future.

Properties of Group 6:

Group 6, numbered by IUPAC style, is a group of elements in the periodic table. Its members are chromium (Cr), molybdenum (Mo), tungsten (W), and seaborgium (Sg). These are all transition metals and chromium, molybdenum and tungsten are refractory metals. The period 8 elements of group 6 are likely to be either unpenthexium (Uph) or unpentoctium (Upo). This may not be possible; drip instability may imply that the periodic table ends around unbihexium. Neither unpenthexium nor unpentoctium have been synthesized, and it is unlikely that this will happen in the near future.

Like other groups, the members of this family show patterns in its electron configuration, especially the outermost shells resulting in trends in chemical behavior:

Z Element No. of electrons/shell
24 chromium 2, 8, 13, 1
42 molybdenum 2, 8, 18, 13, 1
74 tungsten 2, 8, 18, 32, 12, 2
106 seaborgium 2, 8, 18, 32, 32, 12, 2

“Group 6” is the new IUPAC name for this group; the old style name was “group VIB” in the old US system (CAS) or “group VIA” in the European system (old IUPAC). Group 6 must not be confused with the group with the old-style group crossed names of either VIA (US system, CAS) or VIB (European system, old IUPAC). That group is now called group 16.

Properties of Group 7:

Group 7, numbered by IUPAC nomenclature, is a group of elements in the periodic table. They are manganese (Mn), technetium (Tc), rhenium (Re), and bohrium (Bh). All known elements of group 7 are transition metals.

Like other groups, the members of this family show patterns in their electron configurations, especially the outermost shells resulting in trends in chemical behavior.

Properties of Group 8:

Group 8 is a group of chemical element in the periodic table. It consists of  iron (Fe),  ruthenium (Ru),  osmium (Os) and hassium (Hs). They are all transition metals. Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior.

“Group 8” is the modern IUPAC name for this group; the old style name was group VIIIB in the CAS, US system or group VIIIA in the old IUPAC, European system.

Group 8 should not be confused with the old-style group name of VIIIA by CAS/US naming. That group is now called group 18.

Properties of group 9:

Group 9, numbered by IUPAC nomenclature, is a group of chemical element in the periodic table. Members are cobalt (Co), rhodium (Rh), iridium (Ir) and perhaps also the chemically uncharacterized  meitnerium (Mt). These are all transition metals in the d-block. All known isotopes of meitnerium are radioactive with short half-lives, and it is not known to occur in nature; only minute quantities have been synthesized in laboratories.


Z Element No. of electrons/shell
27 cobalt 2, 8, 15, 2
45 rhodium 2, 8, 18, 16, 1
77 iridium 2, 8, 18, 32, 15, 2
109 meitnerium 2, 8, 18, 32, 32, 15, 2 (predicted)

Meitnerium has not been isolated in pure form, and its properties have not been conclusively observed; only cobalt, rhodium, and iridium have had their properties experimentally confirmed. All three elements are typical silvery-white transition metals, hard, and have high melting and boiling points.

Group 10 Properties:

Group 10, numbered by current IUPAC style, is the group of chemical elements in the periodic table that consists of nickel (Ni), palladium (Pd), platinum (Pt), and perhaps also the chemically uncharacterized  darmstadtium (Ds). All are d-block transition metals. All known isotopes of darmstadtium are radioactive with short half-lives, and are not known to occur in nature; only minute quantities have been synthesized in laboratories.

Like other groups, the members of this group show patterns in electron configuration, especially in the outermost shells, although for this group they are particularly weak, with palladium being an exceptional case. The relativistic stabilization of the 7s orbital is the explanation to the predicted electron configuration of darmstadtium, which, unusually for this group, conforms to that predicted by the Aufbau principle.


Z Element No. of electrons per shell
28 nickel 2, 8, 16, 2
46 palladium 2, 8, 18, 18
78 platinum 2, 8, 18, 32, 17, 1
110 darmstadtium 2, 8, 18, 32, 32, 16, 2 (predicted)

Darmstadtium has not been isolated in pure form, and its properties have not been conclusively observed; only nickel, palladium, and platinum have had their properties experimentally confirmed. All three elements are typical silvery-white transition metals, hard, and refractory, with high melting and boiling points.

Properties of Group 11 elements:

Group 11, by modern IUPAC numbering,[1] is a group of chemical elements in the periodic table, consisting of copper (Cu), silver (Ag), and gold (Au). Roentgenium (Rg) is also placed in this group in the periodic table, although no chemical experiments have yet been carried out to confirm that it behaves like the heavier homologue to gold. Group 11 is also known as the coinage metals, due to their former usage. They were most likely the first three elements discovered.[2] Copper, silver, and gold all occur naturally in elemental form.


Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior, although roentgenium is probably an exception:

Z Element No. of electrons/shell
29 copper 2, 8, 18, 1
47 silver 2, 8, 18, 18, 1
79 gold 2, 8, 18, 32, 18, 1
111 roentgenium 2, 8, 18, 32, 32, 17, 2 (predicted)

All Group 11 elements are relatively inert, corrosion-resistant metals. Copper and gold are colored.

These elements have low electrical resistivity so they are used for wiring. Copper is the cheapest and most widely used. Bond wires for integrated circuits are usually gold. Silver and silver-plated copper wiring are found in some special applications.

Properties of the elements of Group 12:

Group 12, by modern IUPAC numbering, is a group of chemical elements in the periodic table. It includes zinc (Zn), cadmium (Cd) and mercury (Hg). The further inclusion of copernicium (Cn) in group 12 is supported by recent experiments on individual copernicium atoms. Group 12 is also known as the volatile metals, although this can also more generally refer to any metal (which need not be in group 12) that has high volatility, such as polonium or flerovium. Formerly this group was named IIB  (pronounced as “group two B”, as the “II” is a Roman numeral) by CAS and old IUPAC system.

The three group 12 elements that occur naturally are zinc, cadmium and mercury. They are all widely used in electric and electronic applications, as well as in various alloys. The first two members of the group share similar properties as they are solid metals under standard conditions. Mercury is the only metal that is a liquid at room temperature. While zinc is very important in the biochemistry of living organisms, cadmium and mercury are both highly toxic. As copernicium does not occur in nature, it has to be synthesized in the laboratory.

Physical and atomic properties

Like other groups of the periodic table, the members of group 12 show patterns in its electron configuration, especially the outermost shells, which result in trends in their chemical behavior:

Z Element No. of electrons/shell
30 zinc 2, 8, 18, 2
48 cadmium 2, 8, 18, 18, 2
80 mercury 2, 8, 18, 32, 18, 2
112 copernicium 2, 8, 18, 32, 32, 18, 2 (predicted)

Group 12 elements are all soft, diamagnetic, divalent metals. They have the lowest melting points among all transition metals. Zinc is bluish-white and lustrous, though most common commercial grades of the metal have a dull finish. Zinc is also referred to in nonscientific contexts as spelter. Cadmium is soft, malleable, ductile, and with a bluish-white color. Mercury is a liquid, heavy, silvery-white metal. It is the only common liquid metal at ordinary temperatures, and as compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.

The table below is a summary of the key physical properties of the group 12 elements. Very little is known about copernicium, and none of its physical properties have been confirmed except for its boiling point (tentative).

Properties of the group 12 elements
Name Zinc Cadmium Mercury Copernicium
Melting point 693 K (420 °C) 594 K (321 °C) 234 K (−39 °C)  ?
Boiling point 1180 K (907 °C) 1040 K (767 °C) 630 K (357 °C) 357+112
−108 K (84+112
−108 °C)
Density 7.14 g·cm−3 8.65 g·cm−3 13.534 g·cm−3  ? 23.7 g·cm−3
Appearance silvery bluish-gray metallic silver-gray silvery  ?
Atomic radius 135 pm 155 pm 150 pm  ? 147 pm

Zinc is somewhat less dense than iron and has a hexagonal crystal structure. The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C. Above 210 °C, the metal becomes brittle again and can be pulverized by beating.  Zinc is a fair conductor of electricity. For a metal, zinc has relatively low melting (419.5 °C, 787.1 F) and boiling points (907 °C). Cadmium is similar in many respects to zinc but forms complex compounds.[15] Unlike other metals, cadmium is resistant to corrosion and as a result it is used as a protective layer when deposited on other metals. As a bulk metal, cadmium is insoluble in water and is not flammable; however, in its powdered form it may burn and release toxic fumes.[16] Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s subshells. As such configuration strongly resists removal of an electron, mercury behaves similarly to noble gas elements, which form weak bonds and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus (see lanthanide contraction). The absence of a filled inner f shell is the reason for the somewhat higher melting temperature of cadmium and zinc, although both these metals still melt easily and, in addition, have unusually low boiling points. Gold has atoms with one less 6s electron than mercury. Those electrons are more easily removed and are shared between the gold atoms forming relatively strong metallic bonds.

Zinc, cadmium and mercury form a large range of alloys. Among the zinc containing ones, brass is an alloy of zinc and copper. Other metals long known to form binary alloys with zinc are aluminium,  antimony, bismuth, gold, iron, lead, mercury,  silver,  tin,  magnesium,  cobalt, nickel,  tellurium and sodium. While neither zinc nor zirconium are ferromagnetic, their alloy ZrZn 2 exhibits ferromagnetism below 35 K. Cadmium is used in many kinds of solder and bearing alloys, due to a low coefficient of friction and fatigue resistance. It is also found in some of the lowest-melting alloys, such as Wood’s metal.[21] Because it is a liquid, mercury dissolves other metals and the alloys that are formed are called amalgams. For example, such amalgams are known with gold, zinc, sodium, and many other metals. Because iron is an exception, iron flasks have been traditionally used to trade mercury. Other metals that do not form amalgams with mercury include tantalum, tungsten and platinum.  Sodium amalgam is a common reducing agent in organic synthesis, and is also used in high-pressure sodium lamps. Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. Since the amalgam reacts with air to give aluminium oxide, small amounts of mercury corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft.

Properties of Group 13:

This is called Boron Group. The boron group are the chemical elements in group 13 of the periodic table, comprising boron (B), aluminium (Al), gallium (Ga), indium (In), thallium (Tl), and perhaps also the chemically uncharacterized nihonium (Nh). The elements in the boron group are characterized by having three electrons in their outer energy levels (valence layers). These elements have also been referred to as icosagens and triels.

Boron is classified as a metalloid while the rest, with the possible exception of nihonium, are considered post-transition metals. Boron occurs sparsely, probably because bombardment by the subatomic particles produced from natural radioactivity disrupts its nuclei. Aluminium occurs widely on earth, and indeed is the third most abundant element in the Earth’s crust(8.3%). Gallium is found in the earth with an abundance of 13 ppm. Indium is the 61st most abundant element in the earth’s crust, and thallium is found in moderate amounts throughout the planet. Nihonium is never found in nature and therefore is termed a synthetic element.

Several group 13 elements have biological roles in the ecosystem. Boron is a trace element in humans and is essential for some plants. Lack of boron can lead to stunted plant growth, while an excess can also cause harm by inhibiting growth. Aluminium has neither a biological role nor significant toxicity and is considered safe. Indium and gallium can stimulate metabolism; gallium is credited with the ability to bind itself to iron proteins. Thallium is highly toxic, interfering with the function of numerous vital enzymes, and has seen use as a pesticide.

Properties of Group 14:

This called Carbon Group. The carbon group is a periodic table group consisting of carbon  (C),  silicon (Si), germanium(Ge), tin (Sn), lead (Pb), and flerovium (Fl).

In modern IUPAC notation, it is called Group 14. In the field of semiconductor physics, it is still universally called Group IV. The group was once also known as the tetrels (from the Greek word tetra, which means four), stemming from the Roman numeral IV in the group names, or (not coincidentally) from the fact that these elements have four valence electrons. The group is sometimes also referred to as tetragens because it has four electrons in its outermost shell or the valence shell. This group is also called the crystallogens.

Chemical Properties:

Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior:

Z Element No. of electrons/shell
6 Carbon 2, 4
14 Silicon 2, 8, 4
32 Germanium 2, 8, 18, 4
50 Tin 2, 8, 18, 18, 4
82 Lead 2, 8, 18, 32, 18, 4
114 Flerovium 2, 8, 18, 32, 32, 18, 4 (predicted)

Each of the elements in this group has 4 electrons in its outer orbital (the atom’s top energy level). The last orbital of all these elements is the p2 orbital. In most cases, the elements share their electrons. The tendency to lose electrons increases as the size of the atom increases, as it does with increasing atomic number. Carbon alone forms negative ions, in the form of carbide (C4−) ions. Silicon and germanium, both metalloids, each can form +4 ions. Tin and lead both are metals while flerovium is a synthetic, radioactive (its half life is very short), element that may have a few noble gas-like properties, though it is still most likely a post-transition metal. Tin and lead are both capable of forming +2 ions.

Carbon forms tetrahalides with all the halogens. Carbon also forms three oxides: carbon monoxide, carbon suboxide (C3O2), and carbon dioxide. Carbon forms disulfides and diselenides.

Silicon forms two hydrides: SiH4 and Si2H6. Silicon forms tetrahalides with fluorine, chlorine, and iodine. Silicon also forms a dioxide and a disulfide. Silicon nitride has the formula Si3N4.

Germanium forms two hydrides: GeH4 and Ge2H6. Germanium forms tetrahalides with all halogens except astatine and forms dihalides with all halogens except bromine and astatine. Germanium bonds to all natural single chalcogens except polonium, and forms dioxides, disulfides, and diselenides. Germanium nitride has the formula Ge3N4.

Tin forms two hydrides: SnH4 and Sn2H6. Tin forms dihalides and tetrahalides with all halogens except astatine. Tin forms chalcogenides with one of each naturally occurring chalcogen except polonium, and forms chalcogenides with two of each naturally occurring chalcogen except polonium and tellurium.

Lead forms one hydride, which has the formula PbH4. Lead forms dihalides and tetrahalides with fluorine and chlorine, and forms a tetrabromide and a lead diiodide, although the tetrabromide and tetraiodide of lead are unstable. Lead forms four oxides, a sulfide, a selenide, and a telluride.

There are no known compounds of flerovium.


The boiling points of the carbon group tend to get lower with the heavier elements. Carbon, the lightest carbon group element, sublimates at 3825 °C. Silicon’s boiling point is 3265 °C, germanium’s is 2833 °C, tin’s is 2602 °C, and lead’s is 1749 °C. The melting points of the carbon group elements have roughly the same trend as their boiling points. Silicon melts at 1414 °C, germanium melts at 939 °C, tin melts at 232 °C, and lead melts at 328 °C.

Carbon’s crystal structure is hexagonal; at high pressures and temperatures it forms diamond (see below). Silicon and germanium have diamond cubic crystal structures, as does tin at low temperatures (below 13.2 °C). Tin at room temperature has a tetragonalcrystal structure. Lead has a face-centered cubic crystal structure.

The densities of the carbon group elements tend to increase with increasing atomic number. Carbon has a density of 2.26 grams per cubic centimeter, silicon has a density of 2.33 grams per cubic centimeter, germanium has a density of 5.32 grams per cubic centimeter. Tin has a density of 7.26 grams per cubic centimeter, and lead has a density of 11.3 grams per cubic centimeter.

The atomic radii of the carbon group elements tend to increase with increasing atomic number. Carbon’s atomic radius is 77 picometers, silicon’s is 118 picometers, germanium’s is 123 picometers, tin’s is 141 picometers, and lead’s is 175 picometers.


Carbon has multiple allotropes. The most common is graphite, which is carbon in the form of stacked sheets. Another form of carbon is diamond, but this is relatively rare. Amorphous carbon is a third allotrope of carbon; it is a component of soot. Another allotrope of carbon is a fullerene, which has the form of sheets of carbon atoms folded into a sphere. A fifth allotrope of carbon, discovered in 2003, is called graphene, and is in the form of a layer of carbon atoms arranged in a honeycomb-shaped formation.

Silicon has two known allotropes that exist at room temperature. These allotropes are known as the amorphous and the crystalline allotropes. The amorphous allotrope is a brown powder. The crystalline allotrope is gray and has a metallic luster.

Tin has two allotropes: α-tin, also known as gray tin, and β-tin. Tin is typically found in the β-tin form, a silvery metal. However, at standard pressure, β-tin converts to α-tin, a gray powder, at temperatures below 13.2° Celsius/56° Fahrenheit. This can cause tin objects in cold temperatures to crumble to gray powder in a process known as tin pest or tin rot.


At least two of the carbon group elements (tin and lead) have magic nuclei, meaning that these elements are more common and more stable than elements that do not have a magic nucleus.


There are 15 known isotopes of carbon. Of these, three are naturally occurring. The most common is stable carbon-12, followed by stable carbon-13. Carbon-14 is a natural radioactive isotope with a half-life of 5,730 years.

23 isotopes of silicon have been discovered. Five of these are naturally occurring. The most common is stable silicon-28, followed by stable silicon-29 and stable silicon-30. Silicon-32 is a radioactive isotope that occurs naturally as a result of radioactive decay of actinides, and via spallation in the upper atmosphere. Silicon-34 also occurs naturally as the result of radioactive decay of actinides.

32 isotopes of germanium have been discovered. Five of these are naturally occurring. The most common is the stable isotope germanium-74, followed by the stable isotope germanium-72, the stable isotope germanium-70, and the stable isotope germanium-73. The isotope germanium-76 is a primordial radioisotope.

40 isotopes of tin have been discovered. 14 of these occur in nature. The most common is the stable isotope tin-120, followed by the stable isotope tin-118, the stable isotope tin-116, the stable isotope tin-119, the stable isotope tin-117, the primordial radioisotope tin-124, the stable isotope tin-122, the stable isotope tin-112, and the stable isotope tin-114. Tin also has four radioisotopes that occur as the result of the radioactive decay of uranium. These isotopes are tin-121, tin-123, tin-125, and tin-126.

38 isotopes of lead have been discovered. 9 of these are naturally occurring. The most common isotope is the primordial radioisotope lead-208, followed by the primordial radioisotope lead-206, the primordial radioisotope lead-207, and the primordial radioisotope lead-204. 4 isotopes of lead occur from the radioactive decay of uranium and thorium. These isotopes are lead-209, lead-210, lead-211, and lead-212.

6 isotopes of flerovium (flerovium-284, flerovium-285, flerovium-286, flerovium-287, flerovium-288, and flerovium-289) have been discovered. None of these are naturally occurring. Flerovium’s most stable isotope is flerovium-289, which has a half-life of 2.6 seconds.

Properties of Group 15:

This group is Pnictogen. Actually Pnictogen is one of the chemical elements in group 15 of the periodic table. This group is also known as the nitrogen family. It consists of the elements nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), and perhaps also the chemically uncharacterized synthetic element moscovium (Mc).

In modern IUPAC notation, it is called Group 15. In CAS and the old IUPAC systems it was called Group VA and Group VB respectively (pronounced “group five A” and “group five B”, “V” for the Roman numeral 5).[2] In the field of semiconductor physics, it is still usually called Group V. The “five” (“V”) in the historical names comes from the “pentavalency” of nitrogen, reflected by the stoichiometry of compounds such as N2O5.

The term pnictogen (or pnigogen) is derived from the Ancient Greek word πνίγειν (pnígein) meaning “to choke”, referring to the choking or stifling property of nitrogen gas.

Properties of group 16:

This group includes chalcogens wich  are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. It consists of the elements oxygen  (O), sulfur(S), selenium  (Se), tellurium (Te), and the radioactive  element polonium  (Po). The chemically uncharacterized  synthetic element  livermorium (Lv) is predicted to be a chalcogen as well. Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term “chalcogen” altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word “chalcogen” is derived from a combination of the Greek word khalkόs (χαλκός) principally meaning copper (the term was also used for bronze/brass, any metal in the poetic sense, ore or coin), and the Latinised Greek word genēs, meaning born or produced.

Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. Selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. All of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell. Their most common oxidation states are −2, +2, +4, and +6. They have relatively low atomic radii, especially the lighter ones.

Lighter chalcogens are typically nontoxic in their elemental form, and are often critical to life, while the heavier chalcogens are typically toxic. All of the chalcogens have some role in biological functions, either as a nutrient or a toxin. The lighter chalcogens, such as oxygen and sulfur, are rarely toxic and usually helpful in their pure form. Selenium is an important nutrient but is also commonly toxic. Tellurium often has unpleasant effects (although some organisms can use it), and polonium is always extremely harmful, both in its chemical toxicity and its radioactivity.

Sulfur has more than 20 allotropes, oxygen has nine, selenium has at least five, polonium has two, and only one crystal structure of tellurium has so far been discovered. There are numerous organic chalcogen compounds. Not counting oxygen, organic sulfur compounds are generally the most common, followed by organic selenium compounds and organic tellurium compounds. This trend also occurs with chalcogen pnictides and compounds containing chalcogens and carbon group  elements.

Oxygen is generally extracted from air and sulfur is extracted from oil and natural gas. Selenium and tellurium are produced as byproducts of copper refining. Polonium and livermorium are most available in particle accelerators. The primary use of elemental oxygen is in steelmaking. Sulfur is mostly converted into sulfuric acid, which is heavily used in the chemical industry. Selenium’s most common application is glassmaking. Tellurium compounds are mostly used in optical disks, electronic devices, and solar cells. Some of polonium’s applications are due to its radioactivity.

Properties of group 17:

The halogens  are a group in the periodic tableconsisting of five chemically related elements:  fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The artificially created element 117 (tennessine, Ts) may also be a halogen. In the modern IUPAC nomenclature, this group is known as  group 17. The symbol X is often used generically to refer to any halogen.

The name “halogen” means “salt-producing”. When halogens react with metals they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide.

The group of halogens is the only periodic table group that contains elements in all three main states of matter at standard temperature and pressure. All of the halogens form acids when bonded to hydrogen. Most halogens are typically produced from minerals or salts. The middle halogens, that is chlorine, bromine and iodine, are often used as disinfectants. Organobromides are the most important class of flame retardants. Elemental halogens are dangerous and can potentially be lethally toxic.

Properties of Group 18:

This is the group of Nobel Gases. The noble gases (historically also the inert gases) make up a group of chemical elementswith similar properties; under standard conditions, they are all odorless, colorless, monatomicgases with very low chemical reactivity. The six noble gases that occur naturally  are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive  radon (Rn). Oganesson (Og) is variously predicted to be a noble gas as well or to break the trend due to relativistic effects; its chemistry has not yet been investigated.

For the first six periods of the periodic table, the noble gases are exactly the members of group 18. Noble gases are typically highly unreactive except when under particular extreme conditions. The inertness of noble gases makes them very suitable in applications where reactions are not wanted. For example, argon is used in light bulbs to prevent the hot tungsten filament from oxidizing; also, helium is used in breathing gas by deep-sea divers to prevent oxygen, nitrogen and carbon dioxide (hypercapnia) toxicity.

The properties of the noble gases can be well explained by modern theories of atomic structure: their outer shell of valence electrons is considered to be “full”, giving them little tendency to participate in chemical reactions, and it has been possible to prepare only a few hundred noble gas compounds. The melting and boiling points for a given noble gas are close together, differing by less than 10 °C (18 °F); that is, they are liquids over only a small temperature range.

Neon, argon, krypton, and xenon are obtained from air in an air separation unit using the methods of liquefaction of gases and fractional distillation. Helium is sourced from natural gas fields which have high concentrations of helium in the natural gas, using cryogenic gas separation techniques, and radon is usually isolated from the radioactive decay of dissolved radium, thorium, or uranium compounds (since those compounds give off alpha particles). Noble gases have several important applications in industries such as lighting, welding, and space exploration. A helium-oxygen breathing gas is often used by deep-sea divers at depths of seawater over 55 m (180 ft) to keep the diver from experiencing oxygen toxemia, the lethal effect of high-pressure oxygen, nitrogen narcosis, the distracting narcotic effect of the nitrogen in air beyond this partial-pressure threshold, and carbon dioxide poisoning (hypercapnia), the panic-inducing effect of excessive carbon dioxide in the bloodstream. After the risks caused by the flammability of hydrogen became apparent, it was replaced with helium in blimps and balloons.


The blocks is classification of adjacent groups in periodic table. The term appears to have been first used by Charles Janet. The respective highest-energy electrons in each element in a block belong to the same atomic orbital type. Each block is named after its characteristic orbital; thus, the blocks are:

  • s-block
  • p-block
  • d-block
  • f-block
  • g-block (hypothetical)

The block names (s, p, d, f and g) are derived from the spectroscopic notation for the associated atomic orbitals: sharp, principal, diffuse and fundamental, and then g which follows f in the alphabet.

The following is the order for filling the “subshell” orbitals, according to the Aufbau principle, which also gives the linear order of the “blocks” (as atomic number increases) in the periodic table:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, …

For discussion of the nature of why the energies of the blocks naturally appear in this order in complex atoms, see atomic orbital and electron configuration.

The “periodic” nature of the filling of orbitals, as well as emergence of the spd and f “blocks” is more obvious, if this order of filling is given in matrix form, with increasing principal quantum numbers starting the new rows (“periods”) in the matrix. Then, each subshell (composed of the first two quantum numbers) is repeated as many times as required for each pair of electrons it may contain. The result is a compressed periodic table, with each entry representing two successive elements:


2s                                                 2p  2p  2p
3s                                                 3p  3p  3p
4s                             3d  3d  3d  3d  3d  4p  4p  4p
5s                             4d  4d  4d  4d  4d  5p  5p  5p
6s 4f  4f  4f  4f  4f  4f  4f  5d  5d  5d  5d  5d  6p  6p  6p
7s 5f  5f  5f  5f  5f  5f  5f  6d  6d  6d  6d  6d  7p  7p  7p

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