Question

How would the composition of an atom change if both the atomic number and mass number each increase by one? A) The atom would have 1 more neutron. B) The atom would have one more proton and electron. C) The atom would have one more proton and one more neutron. D) The atom would have one more proton, one more neutron and one more electron.

Answer 1

Choice-B is the correct one. 

-- The atomic number is the number of protons in the nucleus.
-- Each proton in the nucleus is usually matched by one electron in the 'cloud'.
-- The addition of a proton OR a neutron increases the mass number by 1 .
-- Electrons have such small mass that they don't figure into the atomic mass at all.