Chemistry · Periodic Classification Of Properties · NEET
A chalcogen is any element in Group 16 of the periodic table. The family has five main members: Oxygen (O), Sulphur (S), Selenium (Se), Tellurium (Te), and Polonium (Po). A newer radioactive member, Livermorium (Lv), also sits here. For NEET you mainly need the first five. The name 'chalcogen' means 'ore-forming', because many important ores are oxides and sulphides.
Every chalcogen has the same valence shell pattern: ns2 np4. That means 6 electrons in the outermost shell. For example, Oxygen is 1s2 2s2 2p4, and Sulphur is [Ne] 3s2 3p4. Because the valence configuration is the same, all chalcogens show similar chemical behaviour. This is why they are placed in one vertical column (group).
Valence is found using the rule 'eight minus outer electrons' for non-metals. Chalcogens have 6 outer electrons, so valence = 8 - 6 = 2. This means they gain or share 2 electrons to complete their octet. That is why oxygen forms H2O and sulphur forms H2S, both using 2 bonds.
With 6 outer electrons, a chalcogen needs just 2 more electrons to reach the stable noble gas configuration ns2 np6. When it gains 2 electrons, it reaches the -2 oxidation state, like O(2-) in Na2O or S(2-) in Na2S. This is the most common oxidation state for the lighter members. NEET loves testing that this -2 state gets less common down the group.
Polonium (Po) does not show the -2 state. Going down the group, metallic (electropositive) character increases. Po is the heaviest and most metallic chalcogen, so it prefers to lose electrons rather than gain them. The lighter, more electronegative members (O, S, Se, Te) can still form the -2 state. This is a direct NEET 2024 answer.
Yes, oxygen is a chalcogen and is the first member of Group 16. It behaves a bit differently because it is very small, highly electronegative, and has no d-orbitals in its valence shell. This 'anomalous first member' behaviour is normal in the p-block. Oxygen usually shows only -2 (and -1 in peroxides), while sulphur can show +2, +4, and +6 as well.
As you go down (O to S to Se to Te to Po), atomic size increases and metallic character increases. Oxygen and sulphur are non-metals, selenium and tellurium are metalloids, and polonium is a metal (and radioactive). Because metallic nature grows downward, the -2 state becomes less stable and higher positive states (+4, +6) become more common in the heavier members.
Among Group 16 elements, which one does NOT show the -2 oxidation state?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The name 'chalcogen' comes from Greek and means 'ore-forming'. Many common metal ores exist as oxides and sulphides (for example iron oxide and zinc sulphide), and oxygen and sulphur are Group 16 elements, so the whole family is named after this ore-forming role.
It is ns2 np4, meaning 6 electrons in the outermost shell. Because all members share this configuration, they show similar chemical properties and the same valence of 2.
Chalcogens are Group 16 with configuration ns2 np4, valence 2, and common oxidation state -2. Halogens are Group 17 with configuration ns2 np5, valence 1, and common oxidation state -1. Halogens are more reactive non-metals because they need only 1 electron to complete their octet.
No. Oxygen and sulphur are non-metals, selenium and tellurium are metalloids, and polonium is a radioactive metal. Metallic character increases as you move down the group.
Sulphur commonly shows -2 (as in H2S), +4 (as in SO2), and +6 (as in SO3 and H2SO4). Unlike oxygen, sulphur has vacant d-orbitals, so it can expand its octet and reach higher positive states.
