Answer: Option (b) is the correct answer.
Explanation:
It is known that elements of same group tend to possess same number of valence electrons. As a result, they show same chemical properties.
Phosphorous (P) and chlorine (Cl) belongs to third period. Valence electrons of phosphorous are 5 and chlorine has 7 valence electrons.
Beryllium (Be) and Calcium (Ca) are group 2 elements and both of them have two valence electrons.
Helium (He) is a noble gas and it does not have any valence electrons.
Oxygen (O) has six valence electrons and carbon (C) has 4 valence electrons.
Therefore, we can conclude that berylium (Be) and calcium (Ca) is the pairs of elements have the same number of valence electrons.
