Step-by-step explanation:
It is known that atoms that have same number of valence electrons will show similar chemical properties.
So, when we move from left to right across a period there occurs increase in number of valence electrons of each element. But when we move down a group then number of valence electrons remain the same.
Hence, elements of same group will show similar chemical properties.
Therefore, we can conclude that elements marked as 2 and 3 will have similar chemical properties.