The number of electrons in $[_{19}^{40}K]^{-1}$ is

If $W$ is the mass number and $N$ is the atomic number of an element,then:

Which of the following pairs involves isoelectronic ions?

Calculate the number of protons,neutrons and electrons in $_{35}^{80}Br$.

Which one of the following sets of ions represents a collection of isoelectronic species? (Given: Atomic Number: $F: 9, Cl: 17, Na: 11, Mg: 12, Al: 13, K: 19, Ca: 20, Sc: 21$)

The introduction of a neutron into the nuclear composition of an atom would lead to a change in