Question

There are 15protons and 16neutrons in the neclus of an element calculate its atomic number and mass number

Answer 1

atomic number of any element is the number of protons or electrons present in the atom of an element. An atom,which is electrically neutral, has the number of protons equal to the number of electrons.

the element you are referring to , is Phosphorus(P)

as it has 15 protons in its atom  , its atomic number is 15

On the other hand the atomic mass number of an element is the sum of protons and neutrons present in the nucleus of the atom of that element

as  'P' has a 15 protons and 16 neutrons,

sum of protons and neutrons = 15 + 16 = 31