consider the following isotope of phosphorus:?

Question

31 P
15
How many protons in this atom?
How many neutrons in this atom?
How many electrons in this atom?
Please explain.

Answer 1

Isotopes are the same element with a different number of neutrons.

Thus, this isotope has
15 protons
16 neutrons

Since the charge is 0, P = e, so this isotope has
15 electrons.

Answer 2

Protons = 15
Neutrons = 16 = 31 - 15
Electrons = 15

For an atom to be in the charge neutral state, the number of protons must equal the number of electrons. If there is a imbalance between protons and electrons, caused by gain/loss of electrons it is called an 'ion'. The number of protons is the atomic number, and is indicated by a left subscript number.
The left superscript number is the atomic mass. Atomic mass is the total number of nucleons (protons and neutrons) in the nucleus.As atomic(number of protons)number is given and the atomic mass then the number of neutrons is calculated by subtracting atomic mass from atomic number.
Any difference in this subtraction indicates a different isotope of that element.