Question

Oxygen belongs to which group in the periodic table?

Answer 1

Hint: The group number of an element in the periodic table is identified by identifying the number of electrons in the valence or outermost shell of the atom of the element. The addition of the transition elements in between the S-block and P-block shifted the P-block by 10 groups.

Complete answer:
A group in a periodic table is defined as the vertical series of the elements having the same chemical and physical properties down the column and the elements have a similar electronic configuration down the column of each group. In a group of elements, the last electron enters the same subshell due to which they tend to show similar chemical and physical properties and have the same kind of reactivity.
Whenever we are provided with an element to identify its group number, first of all we need to find out its atomic number. In this case, the atomic number of oxygen is 8. If $np$ electrons are present, then the block is identified as P-block and the group number is identified from the relation:
Group number=$12+np$ electrons.
In the case of oxygen whose electronic configuration is $1s^{2}2s^{2}2p^4$ , the group number is equal to = $12+4=16$
Thus, oxygen belongs to the group 16.

Note:
 While finding the number of $np$ electrons, we need to write the electronic configuration first as the outermost shell of oxygen has 6 electrons and in that case the group number will be equal to (10+6) and not (12+6). Thus, when we write the electronic configuration, we come across the fact that the total number of $np$ electrons in oxygen is 4 and not 6.