Question

What is the valency of magnesium with atomic number 12 and sulphur with atomic number 16?Similarly find out the valencies of the first twenty elements.

Answer 1

both will have valency 2
FIRST TWENTY ELEMENT AND THEIR VALENCY INCLUDE;
HYDROGEN      1
HELIUM             0
LITHIUM             1
BERYLLIUM       2
BORON             3
CARBON          2,4
NITROGEN       3,5
OXYGEN          2     
FLUORINE       1
NEON              0
SODIUM          1
MAGNESIUM   2
ALUMINUM      3
SILICON          4
PHOSPHORUS  3,5
SULFUR             2,4,6
CHLORINE        1,3,5,7
ARGON              0
POTASSIUM        1
CALCIUM            2

Answer 2

Magnesium:- Atomic no. 12

Electronic configuration - 2,8,2

So the valency is = +2

Sulphur :- Atomic no. 16

Electronic configuration - 2,8,6

Valency = -2

Hope Help you ...