Question

Hi, I need a bit of assistance with these problems, it's for today but I'd rather get a good explanation than just the answer. The problems are:

An element has an atomic number of Z = 20 and an atomic mass number A = 40. State how many neutrons and how many electrons it contains.

An element has an atomic number of Z = 30 and an atomic mass number A = 65. State how many neutrons and how many electrons it contains.

Answer 1

Explicación:

Z is the atomic number and tells us the number of electrons the atom has.

A is the massic number and tells us the atom mass. Remember that, if you consider electrons as non-mass particles, the atom mass is due to protons and neutrons.

Z=20 A=40 means 20 electrons (therefore 20 protons) and so it must have 20 neutrons.

Z= 30 A=65 means 30 electrons (and 30 protons) and as its mass must be 65, it has 35 neutrons.