Question

What happens to the number of valence electrons when we move down in the group?

Answer 1

We need to know that the electrons present in the outermost shell of an atom are known as valence electrons. For example, the number of valence electrons of oxygen is equal to six. Two electron in $2s$subshell and four electron present in the $2p$ subshell. If the outer shell is not closed, these valence electrons can be included in the formation of chemical bonds. The number of electrons will be different for each element which is present in the different groups and periods.

Complete answer:
We also know that the number of valence electrons will remain the same when moving down in the group. Which means, all the elements present in the same group exhibit the same number of valence electrons.
The electrons present in the outermost shell of an atom are known as valence electrons. The number of valence electrons is increasing when moving across a period. But in the case of groups, it will remain same. And the elements present in the same group will show the same valency due to the presence of the same number of valence electrons. The number of valence electrons depends on the valency. In the case of period, the number of valence electron is increasing. Hence, the number of valence is also increasing.

Note:
We have to remember that the number of valence electrons increases across a period and remains the same when moving down the group. The valence electron can predict the chemical properties of an element. The electronic configuration is mainly dependent on the reactivity of an element. In the case of transition metals, the valence electrons are present in the inner shells. But in main group elements, it exists in the outermost electron shell.