An element has the electronic configuration 2, 8, 2. To which group and period of the modern periodic table does it belong?

1. The number of valence electrons is 2, so it is in group 2. 2. Three shells (K, L, M) are occupied, so it is in period 3. 3. Therefore the element is in group 2, period 3 (it is magnesium). 4. Rule out A and C: those misread the shell count or valence electrons. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 2 "Periodic Classification of Elements", p.37_