Question

Four elements A, B, C and D have atomic numbers 4, 9, 11 and 20 respectively.
i) Choose the element that has one electron in the outermost shell and write its electronic
configuration
ii) Choose two elements that belong to the same group. Give reason for your choice.
iii) Write the formula of the compound formed by the combination of element C and
element X. (Atomic number of X = 8)​

Answer 1

Answer:

i) C ii) A and D iii)C₂X

Explanation:

i) Electronic configuration of C = 2,8,1

Hence C has 1 electron in its outermost shell.

ii) A and  D

Electronic configuration of A = 2,2

Electronic configuration of D = 2,8,8,2

Same group have same no of valence electron in their outermost shell. So, A and D belong to same group.

iii) Electronic configuration of C = 2,8,1

Electronic configuration of X = 2,6

So , 1 element of X reacts with 2 elements of C to form a stable compound.

Compound formula = C₂X