An atom has 6 protons and neutrons in its nucleus find the mass number and number of electrons

Z=atomic number=number of protons=6

A=mass number

N=number of neutrons=6

A=Z+N

A=6+6=12

the number of electrons is Z, if the atom is electracally neutral.

Therefore; the mas number (A) = 6, the number of electrons is 6

The mass number is 12, obviously, since it has 6 protons and neutrons each, and each one counts as 1 atomic mass units, so 6+6 = 12. The number of electrons, if the atom is not an ion, should be equal to the number of protons, so the answer to the number of electrons is 6.