Which character is different for the two isotopes of an element?

Identify the isoelectronic pair from the following.

The atomic number of an element is always equal to

Which of the following is not a hydrogen-like species?

The nitrogen atom has $7$ protons and $7$ electrons. The nitride ion $(N^{3-})$ will have:

An ion with mass number $37$ possesses one unit of negative charge. If the ion contains $11.1 \%$ more neutrons than the electrons,find the symbol of the ion.