Chapter 1, Problem 1E.21E

(a)

Interpretation Introduction

Interpretation:

The number of unpaired electrons present in bismuth atom has to be predicted.

Concept Introduction:

Electronic configuration: The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.

Electrons occupy the lowest energy orbitals. The increasing order of orbital energy is $s,p,dandf.$  The lowest energy orbital is $ls.$

The energy order of the orbital for the first three periods is as follows,

    $ls,2s,2p,3s,and3p.$

The orbital which is closer to the nucleus has lower energy; therefore the $2s$ is lower in energy than $3s.$   Accordingly $2s$ is lower in energy than $2pand4s$ is lower in energy than $3d.$

In general, the orbitals can hold maximum of two electrons, the two electrons must have opposite spin.

The subshell ordering by Aufbau principle is given below,

$ls,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s,5f,6d,7p,8s,\mathrm{...}$

(b)

Interpretation Introduction

Interpretation:

The number of unpaired electrons present in silicon atom has to be predicted.

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

Interpretation:

The number of unpaired electrons present in tantalum atom has to be predicted.

Concept Introduction:

Refer to part (a).

(d)

Interpretation Introduction

Interpretation:

The number of unpaired electrons present in nickel atom has to be predicted.

Concept Introduction:

Refer to part (a).