Answer
(a) 1.00
(b) 1.00
(c) 1.25
(d) 1.46
(e) 1.54
Work Step by Step
The number of neutrons (N) = A-Z where A is the mass number and Z is the atomic number.
The number of protons (P)= Z where Z is the atomic number. Therefore, the neutron-to-proton ratio $(\frac{N}{P})$ is given by the expression
$\frac{N}{P}=\frac{A-Z}{Z}$.
(a) $\frac{N}{P}=\frac{A-Z}{Z}=\frac{12-6}{6}=1.00$
(b) $\frac{N}{P}=\frac{40-20}{20}=1.00$
(c) $\frac{N}{P}=\frac{90-40}{40}=1.25$
(d) $\frac{N}{P}=\frac{138-56}{56}=1.46$
(e) $\frac{N}{P}=\frac{208-82}{82}=1.54$
