Which property of an element is always a whole number?

Match the following columns:

$(i) \ _{26}Fe^{54}, \ _{26}Fe^{56}, \ _{26}Fe^{58}$	$(a) \ \text{Isotopes}$
$(ii) \ _1H^3, \ _2He^3$	$(b) \ \text{Isotones}$
$(iii) \ _{32}Ge^{76}, \ _{33}As^{77}$	$(c) \ \text{Isoelectronic}$
$(iv) \ _{92}U^{235}, \ _{90}Th^{231}$	$(d) \ \text{Isobars}$
$(v) \ _1H^1, \ _1D^2, \ _1T^3$

Which of the following are pairs of isotopes?

List the isotopes of hydrogen,carbon,and chlorine,and specify the number of protons,electrons,and neutrons for each.

Substances which have identical chemical properties but differ in atomic weights are called

State whether the following statements are true or false:
$(i)$ Isobars have different atomic numbers.
$(ii)$ $_{14}^{30}\text{Si}$,$_{16}^{32}\text{S}$ are isotones.
$(iii)$ Niels Bohr was the first to suggest that the atom is spherical.
$(iv)$ Rutherford's model is accepted as the nuclear model of the atom.