Question

Consider the series of elements below. Which series contains ONLY elements with one lone pair of electrons in their Lewis symbol.

A. N,O,F

B. N,P, As

C. F,Cl,Br

D. Li, Na, K

E. None of the above

Please explain why the answer is B and why it can’t be C or D. Thank you

Answer 1

PS:- i got your confusion, so lone pair means a pair of electron in valance cell, the electron should be paired and question asking for elements which have only single lone pair.

we will go one by one each option

lone pair refers to a pair of valenceelectrons that are not shared with another atom and is sometimes called a non-bonding pair

A)

lewis structure

while writing the electron distribution of these atoms

N - 1S², 2S², 2P¹ or

now we can see the in the outer cell, n=2 there is one pair of electron and three unpaired electron. so it has only one lone pair.

O-

the outer cell n=2 , had 2 lone pairs and 2 unpaired electron.

similarly F has 3 lone pairs and one unpaired electron.

B)

lewis structure of the N, P and As is shown below

  

for N, we have discussed above it has one lone pair and three unpaired electron.

P-   

it has one lone pair and three unpaired electron.

similarly As has one lone pair and three unpaired electron.

C)

lewis structure of F,Cl,Br are shows

each of the above atoms contains 5 valance electron.

F- we have already discussed about F, it has 3 lone pair and one unpaired electron

D) Li -

  

it has one single unpaired electron in outer cell.