Position of oxygen in periodic table

1. Oxygen is the first member of the group VIA and sulphur is the second member of the group VIA.

2. Other member of this group are selenium, tellurium and polonium.

3. Members of group VIA have 6 electrons in their valence shell. They generally show a valency of -2. Oxygen shows a fixed valency of 2 while sulphur shows variable valencies of 2, +4 and +6 also.

4. All the members of this group are non-metals. The metallic character of the group increases down the group. Polonium is radioactive metal.

5. The members of group VIA show allotropy. For example: the allotropes of oxygen are O₂ (dioxygen) and O₃ (ozone). Allotropes of sulphur are rhombic, monoclinic, plastic and colloidal.

6. The first four members of this group are often called chalcogens (meaning ore forming elements) since they form the oxide and sulphide ores of many metals.