Q: (i) Write the electronic configurations of the following ions: (a) \$\displaystyle { H }^{ - }(b){ Na }^{ + }(c){ O }^{ 2- }(d){ F }^{ - }\$. (ii) What are the atomic numbers of elements whose outermost electrons are represented by \$\displaystyle (a){ 3s }^{ 1 }(b){ 2p }^{ 3 }\$ and \$(c){ 3d }^{ 1 }\$ ?(iii) Which atoms are indicated by the following configurations ? (a) \$\displaystyle \left[ He \right] 2{ s }^{ 1 }\$ (b) \$\displaystyle \left[ Ne \right] { 3s }^{ 2 }{ 3p }^{ 3 }\$ (c) \$\displaystyle \left[ Ar \right] { 4s }^{ 2 }{ 3d }^{ 1 }\$

(i) (a) The electronic configuration of \$\displaystyle { H }^{ - }\$ is \$\displaystyle 1{ s }^{ 2 }\$(b)The electronic configuration of \${ Na }^{ + }\$ is \$\displaystyle 1{ s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }\$(c)The electronic configuration of \${ O }^{ 2- }\$ is \$\displaystyle 1{ s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }\$(d) The electronic configurations of \${ F }^{ - }\$ is \$\displaystyle 1{ s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }\$(ii) The atomic numbers of elements whose outermost electrons are represented by \$\displaystyle (a){ 3s }^{ 1 }(b){ 2p }^{ 3 }and\quad (c){ 3d }^{ 1 }\$ are 11 (Na), 7 (N) and 21 (Sc) respectively.(iii) The following configurations indicates(a) \$\displaystyle \left[ He \right] 2{ s }^{ 1 }\$ (b) \$\displaystyle \left[ Ne \right] { 3s }^{ 2 }{ 3p }^{ 3 }\$ (c) \$\displaystyle \left[ Ar \right] { 4s }^{ 2 }{ 3d }^{ 1 }\$(a) Li \$(Z=3)\$, (b) P\$ (Z=15)\$ and (c) Sc \$Z=21)\$ respectively.

Q: Electronic configuration of copper (atomic No.Cu-29) is :

This is expected that the configuration of copper is \$3d^9 4s^2\$. However, it turns out that the \$3d^{10} 4s^1\$ configuration is more stable, because that way the 3d subshell is full, which is a far more stable arrangmemnt than \$3d^9\$.Due to extra stability of half filled and full filled orbital, Cu have configuration \$1s^22s^22p^63s^23p^63d^{10}4s^14p^0\$.

Q: Four quantum numbers of unpaired electron of chlorine are :

The electronic configuration of chlorine is \$\displaystyle 1s^22s^22p^63s^23p^5 \$.The unpaired electron of Cl belongs to 3p orbital. For a p orbital, \$\displaystyle l=1\$ and \$\displaystyle m=-1, \: 0 \: or +1 \$.Four quantum numbers of unpaired electron of chlorine are \$\displaystyle n=3, l =1,m=0,s=+1/2\$.

Question 1

State Hund's rule of maximum multiplicity.

Accepted Answer

Hund's Rule of Maximum Multiplicity rule states that for a given electron configuration, the term with maximum multiplicity falls lowest in energy. According to this rule electron pairing in p, d and f orbitals cannot occur until each orbital of a given subshell contains one electron each or is singly occupied.

Question 2

Explain Hund's rule with an example.

Accepted Answer

Hund's rule : Every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied and all electrons in singly occupied orbitals have the same spin. The image attached is the example of hund's rule.

Question 3

Give reason why half filled or fully filled orbitals provide more stability to the molecules?

Accepted Answer

The exactly half-filled and fully filled orbitals have greater stability than other configurations. The reason for their stability are symmetry and exchange energy. The electrons present in the different orbitals of the same sub-shell can exchange their positions.

Question 4

Consider the ground state of Cr atom (Z = 24). The numbers of electrons with the azimuthal quantum  numbers, $l$ = 1 and 2 are, respectively:

Accepted Answer

The electronic configuration of Cr along with the values of the quantum numbers $n$ and $l$ are shown.$n$ $l$$1{ s }^{ 2 }$$1$      $0$$2{ s }^{ 2 }$$2$$0$$2{ p }^{ 6 }$     $2$$1$$3{ s }^{ 2 }$$3$$0$$3{ p }^{ 6 }$$3$$1$$3{ d }^{ 5 }$$3$$2$$4{ s }^{ 1 }$$4$$0$Thus the number of electrons with $l=1$ is $12$and the number of electrons with $l=2$ is $5$

Question 5

(i) Write the electronic configurations of the following ions: (a) $H^{-} (b) N a^{+} (c) O^{2 -} (d) F^{-}$ .
(ii) What are the atomic numbers of elements whose outermost electrons are represented by $(a) 3 s^{1} (b) 2 p^{3}$ and $(c) 3 d^{1}$ ?
(iii) Which atoms are indicated by the following configurations ?
(a) $[H e] 2 s^{1}$ (b) $[N e] 3 s^{2} 3 p^{3}$ (c) $[A r] 4 s^{2} 3 d^{1}$

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Accepted Answer

(i) (a) The electronic configuration of $\displaystyle { H }^{ - }$ is  $\displaystyle 1{ s }^{ 2 }$(b)The electronic configuration of ${ Na }^{ + }$ is $\displaystyle 1{ s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }$(c)The electronic configuration of ${ O }^{ 2- }$ is $\displaystyle 1{ s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }$(d) The electronic configurations of ${ F }^{ - }$ is $\displaystyle 1{ s }^{ 2 }{ 2s }^{ 2 }{ 2p }^{ 6 }$(ii) The atomic numbers of elements whose outermost electrons are represented by $\displaystyle (a){ 3s }^{ 1 }(b){ 2p }^{ 3 }and\quad (c){ 3d }^{ 1 }$ are 11 (Na), 7 (N) and 21 (Sc) respectively.(iii) The following configurations indicates(a) $\displaystyle \left[ He \right] 2{ s }^{ 1 }$ (b) $\displaystyle \left[ Ne \right] { 3s }^{ 2 }{ 3p }^{ 3 }$ (c) $\displaystyle \left[ Ar \right] { 4s }^{ 2 }{ 3d }^{ 1 }$(a) Li $(Z=3)$, (b) P$ (Z=15)$ and (c) Sc $Z=21)$ respectively.

Question 6

The electronic configuration of potassium is $2, 8, 8, 1$ and not $2, 8, 9$.

Accepted Answer

According to octet rule, the outermost shell of an atom can accommodate maximum 8 electrons (except K shell which can accommodate maximum 2 electrons). Hence, the electronic configuration of potassium is $2, 8, 8, 1$ and not $2, 8, 9$.

Question 7

Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

Accepted Answer

the following rules are followed for writing the number of electrons in different energy levels or shells.(i) the maximum number of electrons presents in a shell is given by the formula $ 2n^2 $ where $  'n' $ is the orbit number of energy level index $ 1, 2, 3 ...$ hence the maximum number of electrons in different shells are as follows : First orbit or K-shell will be $ = 2 \times 1^2 \times 2 $ Second orbit or L shell will be $  = 2 \times 2^2 =  8 $ third orbit or M shell will be $ = 2 \times 3^2 = 18 $ fourth orbits or N-Shell will be $ = 2 \times 4^2 = 32 $ and so on.(ii) The maximum number of electrons that can be accommodated in the outermost orbit is $ 8 $(iii) Electrons are not accommodated in a given shell unless the inner shells are filled. That is the shells are filled in a stepwise manner.

Question 8

The correct order of increasing energy of atomic orbital is:

Accepted Answer

Based on Aufbau principle, we can find the order of increasing energy of atomic orbitalSo, 5p<6s<4f<5d

Question 9

Electronic configuration of copper (atomic No.Cu-29) is :

Accepted Answer

This is expected that the configuration of copper is $3d^9 4s^2$. However, it turns out that the $3d^{10} 4s^1$ configuration is more stable, because that way the 3d subshell is full, which is a far more stable arrangmemnt than $3d^9$.Due to extra stability of half filled and full filled orbital, Cu have configuration $1s^22s^22p^63s^23p^63d^{10}4s^14p^0$.

Question 10

Four quantum numbers of unpaired electron of chlorine are :

Accepted Answer

The electronic configuration of chlorine is $\displaystyle 1s^22s^22p^63s^23p^5 $.The unpaired electron of Cl belongs to 3p orbital. For a p orbital, $\displaystyle  l=1$ and $\displaystyle m=-1,  \: 0 \: or +1 $.Four quantum numbers of unpaired electron of chlorine are $\displaystyle n=3, l =1,m=0,s=+1/2$.

Revise with Concepts

Electron Configuration

Quick Summary With Stories

Hund's Rule of Maximum Multiplicity

Electronic Configuration of Atoms-s, p, d, f

Stability of Half Filled and Completely Filled Orbitals

State Hund's rule of maximum multiplicity.

Explain Hund's rule with an example.

Give reason why half filled or fully filled orbitals provide more stability to the molecules?

Consider the ground state of Cr atom (Z = 24). The numbers of electrons with the azimuthal quantum numbers, $l$ = 1 and 2 are, respectively:

The electronic configuration of potassium is $2, 8, 8, 1$ and not $2, 8, 9$ .

Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

The correct order of increasing energy of atomic orbital is:

Electronic configuration of copper (atomic No.Cu-29) is :

Four quantum numbers of unpaired electron of chlorine are :

Revise with Concepts

Electron Configuration

Quick Summary With Stories

Hund's Rule of Maximum Multiplicity

Electronic Configuration of Atoms-s, p, d, f

Stability of Half Filled and Completely Filled Orbitals

State Hund's rule of maximum multiplicity.

Explain Hund's rule with an example.

Give reason why half filled or fully filled orbitals provide more stability to the molecules?

Consider the ground state of Cr atom (Z = 24). The numbers of electrons with the azimuthal quantum numbers, l = 1 and 2 are, respectively:

The electronic configuration of potassium is 2,8,8,1 and not 2,8,9.

Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

The correct order of increasing energy of atomic orbital is:

Electronic configuration of copper (atomic No.Cu-29) is :

Four quantum numbers of unpaired electron of chlorine are :

Consider the ground state of Cr atom (Z = 24). The numbers of electrons with the azimuthal quantum numbers, $l$ = 1 and 2 are, respectively:

The electronic configuration of potassium is $2, 8, 8, 1$ and not $2, 8, 9$ .