Which of the following is an isotonic pair?

Elements having different nuclear charge but the same mass number are called

$_{20}X^{40}$ and $_{21}X^{40}$ are

An atom is composed of protons,neutrons,and electrons. If the mass of a neutron is halved and the mass of an electron is doubled,what will be the change in the mass of the nucleus of $_6C^{12}$?

Match the following columns:

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

In a neutral atom,which particles are equivalent in number?