Question

Without referring to the periodic table,name the elements,give their electronic structure and name the group in the periodic table to which the following atomic number belong
3,9,12,17,20

Answer 1

Atomic number 3 - Lithium 1s²2s¹, group 1

Atomic number 9 - Fluorine 1s²2s²2p⁵, group 17

Atomic number 12 - Magnesium, 1s²2s²2p⁶3s², group 2

Atomic number 17 - Chlorine, 1s²2s²2p⁶3s²3p⁵, group 17

Atomic number 20 - Calcium, 1s²2s²2p⁶3s²3p⁶4s², group 2