Question

How many valence electrons does an atom of lithium possess?
[A] 1
[B] 2
[C] 3
[D] 4

Answer 1

HINT: Valence electrons are the electrons present in the outermost shell of an atom. To find the number of valence electrons in an atom of lithium you have to know that atomic number of lithium. You can use the atomic number to write down its electronic configuration and then find the electrons in the valence shell.

COMPLETE STEP BY STEP SOLUTION: To answer this question we need to understand the meaning of the term valence.
Electrons in the valence shell of an atom are known as valence electrons. The valence shell is the outermost shell of an atom. The electrons in this outermost shell are responsible for the bonding of the atoms.
The atoms attain stability by filling their octet (or duplet in case of hydrogen atom as it has only one electron) and attaining a stable configuration.
To find the number of valence electrons in lithium we need to know its atomic number so that we can write down its electronic configuration.
Atomic number of lithium is 3. It will have two electrons in the first shell and 1 electron in the next shell which is its valence shell.
Therefore, we can write down its electronic configuration as- 2, 1. So, there is one electron in its outermost shell.
We can understand from the above discussion that lithium as one electron in its valence shell which makes it valence electrons.

Therefore, the correct answer is option [A] 1.


NOTE: Lithium has only one electron in its outermost shell. To gain stable configuration it will need to gain seven electrons. Losing one electron is more favourable energetically than gaining seven electrons and due to small size there will be electron-electron repulsion causing instability. Therefore, lithium exists in a stable ion form as $L{i}^{+}$ by losing one electron.