Which of these elements has physical and chemical properties most similar to silicon (si)?
(1) germanium (ge) (3) phosphorus (p)
(2) lead (pb) (4) chlorine (cl)

Option (1) and (2) are correct.

Explanation:

Elements which contain same number of valence electrons tend to show similar chemical properties. This is because having same number of valence electrons will make the atoms to react in a similar way.

For example, Silicon is a group 14 element. So, it contains only 4 valence electrons. Similarly, germanium and lead are group 14 elements and it has 4 valence electrons.

Therefore, silicon, germanium, and lead will have similar chemical properties.

Whereas phosphorous is a group 15 element, and chlorine is a group 17 element.

Thus, we can conclude that out of the given options germanium and lead elements has physical and chemical properties most similar to silicon (Si).