A certain neutral atom has an atomic number = 19 and a mass number = 39.Which of the following are correct?
1)It has 19 electrons.
2)It has 20 protons.
3)It has 20 neutrons.
4)It has a total of 39 protons and electrons.

Question

Quizplus · Accepted Answer

Atomic number represents the number of protons in an atom which is 19 in this case.
Therefore, the number of electrons will also be 19 for a neutral atom (number of electrons = number of protons in a neutral atom).
Mass number represents the sum of protons and neutrons in the atom which is 39 in this case.
Thus, the number of neutrons can be obtained by subtracting the atomic number from the mass number i.e. 39 - 19 = 20.
Therefore, statement 1 and 3 are correct while statement 2 and 4 are incorrect.

A Certain Neutral Atom Has an Atomic Number = 19