Calculate the number of neutrons in atoms of the isotope 3919K
With working out

20 neutrons

Explanation:

In the atom of an element, there exists three subatomic particles namely; proton, neutron and electron etc. The sum of the number of neutrons and number of protons (a.k.a atomic number) in an atom makes up the mass number.

In this question, an element was given as follows: 39- 19 K meaning that the mass number is 39 but the atomic number is 19.

Hence,

no of. neutrons = mass no. - atomic no.

39 - 19 = 20 neutrons.

if you look up in the top right corner you'll see your current profile picture, click than click "view profile" you'll be able to change it there.