Question

To which group in the periodic table does lithium belong? How many valence electrons does it have?

Answer 1

It is present in the same group in which sodium is present. In the second period because it is very small in size that’s why it can be present in the beginning groups. It has properties like metals and has one electron in the outermost shells. It has atomic number $3$ so by Pauli's exclusion principle it has two electrons in the first shell and remaining one electron in the outermost shell.

Complete step-by-step answer:
Lithium is present in group $1$ and period $2$ . It has properties similar to sodium, potassium etc. It has an electronic configuration $Li(3) = \,1{s^2}\,2{s^1}$ and like all other metals it can lose one electron from its outermost shell.
$Li\xrightarrow{{Oxidation}}L{i^ + }\, + \,{e^ - }$

In the above half-cell equation, lithium is oxidized from $Li$ to $L{i^ + }$ by losing one electron thus it is a very good reducing agent. If we see sodium it also has one unpaired electron in the outermost shell and which makes it a very good reducing agent so the elements present in group one which is known as “Alkali metals” all are good reducing agents.

Group $1$ forms by elements Hydrogen $(H)$ , lithium $(Li)$ , sodium $Na$, potassium $(K)$, rubidium $(Rb)$ and cesium $(Cs)$. All the elements have one unpaired electron in the outermost shell but period is different for all.

Note: As lithium has one unpaired electron in its outermost shell so this property of it makes it a very good reducing agent like all other metals. Its chemical properties make it a very good base when dissolved in water. Its electronic configuration is according to Pauli's exclusion principle and Hund’s rule.