Classification of Elements and Periodicity in Properties Questions and Answers Part-4

1. Which of the following is isoelectronic with carbon atom?
a) \[Na^{+}\]
b) \[AI^{3+}\]
c) \[O^{2-}\]
d) \[N^{+}\]

Answer: d
Explanation: \[N^{+}\]

2. \[Na^{+}, Mg^{++}, AI^{3+}  and     Si^{4+}\]       are isoelectronic. The order of theirionic size is
a) \[Na^{+}>Mg^{++}<AI^{3+}<Si^{4+}\]
b) \[Na^{+}<Mg^{++}>AI^{3+}>Si^{4+}\]
c) \[Na^{+}>Mg^{++}>AI^{3+}>Si^{4+}\]
d) \[Na^{+}<Mg^{++}>AI^{3+}<Si^{4+}\]

Answer: c
Explanation: Among the isoelectronic species, the cation having more positive charge would be the smaller in size.

3. Electron affinity depends on
a) atomic size
b) nuclear charge
c) atomic number
d) atomic size and nuclear charge both

Answer: d
Explanation: Electron affinity depends on atomic size and nuclear charge both

4. The element with highest electron affinity among halogens is
a) F
b) Cl
c) Br
d) I

Answer: b
Explanation: Cl

5. The correct order of electron affinity among the following is
a) F > Cl > Br
b) Br > Cl > F
c) Cl > F > Br
d) F > Br > Cl

Answer: c
Explanation: Cl > F > Br

6. Highest electron affinity is shown by
a) \[O^{-}\]
b) \[F^{-}\]
c) \[CI_{2}\]
d) \[F_{2}\]

Answer: a
Explanation: Due to inert gas configuration molecules F2 , Cl2 and anion F- have almost zero electron affinity

7. Which of the following has least electron afinity?
a) Oxygen
b) Argon
c) Nitrogen
d) Boron

Answer: b
Explanation: Argon

8. Which of the following has highest electron affinity?
a) \[Li^{+}\]
b) \[Na^{+}\]
c) \[F^{-}\]
d) \[CI^{-}\]

Answer: a
Explanation: Addition of an electron to F- and Cl- ions will involve repulsions whereas in case of Na+ ion, hence EA of Li+ is highest among these.

9. The element having very high ionizaiton energy but zero electron affinity is
a) H
b) F
c) He
d) Be

Answer: c
Explanation: He has zero EA because of its completely filled subshells (1s2 2s2 )

10. The lower electron affinity of fluorine than that of chlorine is due to
a) smaller size
b) smaller nuclear charge
c) difference in their electronic configurations
d) its highest reactivity

Answer: a
Explanation: Since F has small size and its relatively compact 2 p-subshell’s electron-electron repulsion, do not allow the addition of an extra electron whereas Cl has bigger size than F, allows the addition of an extra electron more easily.