Question

The atomic number of an element Z is 20. State

1. the number of valence electron(s) in the element.
2. the position of Z in the periodic table.
3. whether the element is a metal or a non-metal.
4. State the formula of the compound between Z and hydrogen.

Answer 1

1. The two valence electrons are present in the element having atomic number 20.
2. the position of Z in the periodic table is 4^th period and group 2.
3. The element is metal.
4. Valency of Z is 2, so it combines with hydrogen (valency 1) to form ZH₂ (By criss-cross method).