Question

Do both members of the following pairs have the same number of protons? Neutrons? Electrons?

$\left(a\right)\mathbf{}{}_{\mathbf{1}}{}^{\mathbf{3}}\mathit{H}\mathbf{}\mathit{a}\mathit{n}\mathit{d}\mathbf{}{}_{\mathbf{2}}{}^{\mathbf{3}}\mathit{H}\mathit{e}\mathbf{}\left(b\right)\mathbf{}{}_{\mathbf{6}}{}^{\mathbf{14}}\mathit{C}\mathbf{}\mathit{a}\mathit{n}\mathit{d}\mathbf{}{}_{\mathbf{7}}{}^{\mathbf{15}}\mathit{N}\mathbf{}\left(c\right)\mathbf{}{}_{\mathbf{9}}{}^{\mathbf{19}}\mathit{F}\mathbf{}\mathit{a}\mathit{n}\mathit{d}\mathbf{}{}_{\mathbf{9}}{}^{\mathbf{18}}\mathit{F}\mathbf{}$

Which pair(s) consist(s) of atoms with the same Z value? N value? A value?

Short answer

All the elements of the isotopic pair don’t acquire an equal number of protons, electrons, and neutrons.

Only ${}_9{}^{19}Fand{}_9{}^{18}F$have the same atomic number, protons, and electrons.

Step-by-step solution

Calculation of Z, N, and A in part (a)

${}_1{}^{3}Hand{}_2{}^{3}He$

${}_1{}^{3}H$Atomic number = 1, Protons = 1, Electrons = 1,

Atomic mass = 3

Neutrons = Atomic mass – Protons = 3 – 1 = 2

${}_2{}^{3}He$Atomic number = 2, Protons = 2, Electrons = 2,

Atomic mass = 3

Neutrons = Atomic mass – Protons = 3 – 2 = 1

${}_1{}^{3}Hand{}_2{}^{3}He$have different numbers of protons, electrons, and neutrons.

Calculation of Z, N, and A in part (b) 

${}_6{}^{14}Cand{}_7{}^{15}N$

${}_6{}^{14}C$Atomic number = 6, Protons = 6, Electrons = 6,

Atomic mass = 14

Neutrons = Atomic mass – Protons = 14 – 6 = 8

${}_7{}^{15}N$Atomic number = 7, Protons = 7, Electrons = 7,

Atomic mass = 15

Neutrons = Atomic mass – Protons = 15 – 7 = 8

${}_6{}^{14}Cand{}_7{}^{15}N$both have different numbers of protons and electrons but have the same number of neutrons.

Calculation of Z, N, and A in part (c)

${}_6{}^{14}Cand{}_7{}^{15}N$

${}_9{}^{19}F$ Atomic number = 9, Protons = 9, Electrons = 9,

Atomic mass = 19

Neutrons = Atomic mass – Protons = 19 – 9 = 10

${}_9{}^{18}F$Atomic number = 9, Protons = 9, Electrons = 9,

Atomic mass = 18

Neutrons = Atomic mass – Protons = 18 – 9 = 9

${}_9{}^{19}Fand{}_9{}^{18}F$ both have the same atomic number, protons, and electrons but different atomic mass and neutron