Question

Which of the following are example of mirror isobars?

• A. ${}_1^{1}H\text{and}{}_1^{2}H$
• B. ${}_6^{12}C\text{and}{}_6^{13}C$
• C. ${}_{11}^{23}Na\text{and}{}_{12}^{23}Mg$
• D. ${}_{11}^{23}Na\text{and}{}_{12}^{24}Mg$

Answer 1

The correct option is C ${}_{11}^{23}Na\text{and}{}_{12}^{23}Mg$

(a)

${}_1^{1}H:\text{A=1, Z= 1}$

$⟹\text{protons=1, neutrons = 0}$

${}_1^{2}H:\text{A=2, Z= 1}$

$⟹\text{protons=1, neutrons = 1}$

(b)

${}_6^{12}C:\text{A=12, Z= 6}$

$⟹\text{protons=6, neutrons = 6}$

${}_6^{13}C:\text{A=13, Z= 7}$

$⟹\text{protons=6, neutrons = 7}$

(c)

${}_{11}^{23}Na:\text{A=23, Z= 11}$

$⟹\text{protons=11, neutrons = 12}$

${}_{12}^{23}Mg:\text{A=23, Z= 12}$

$⟹\text{protons=12, neutrons = 11}$

(d)

${}_{11}^{23}Na:\text{A=23, Z= 11}$

$⟹\text{protons=11, neutrons = 12}$

${}_{12}^{24}Mg:\text{A=24, Z= 12}$

$⟹\text{protons=12, neutrons = 12}$

In (c), both have same mass numbers and the number of protons and neutrons are exchanged. Hence, they are mirror isobars.