Question

.one atom of an element consists of 19 protons and 20 neutrons. mass number of the element will be (1) 29 (2) 20 (3) 39 (4) none of these​

Answer 1

Answer:

39

Explanation:

mass number = number of protons + number of neutron

A=20+19

=39

Answer 2

Answer:

3)39

Explanation:

Mass of an atom = sum of number of protons in an atom and number of neutrons in an atom

19+20=39