Are Li, Na and K in the same group

Yes, they are.

Explanation:

Yes, they are. Li, Na, and K are referring to  Lithium, sodium, and potassium.

They are all belonging to the same group which is called the alkali metals group.

They are having the same number of valence electrons i.e. 1.

This group of the alkali metals are considering tree more metals in it which are Rb, Cs, and Fr.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.