An ion has three neutrons, four protons, and a charge of positive one. how many electrons are there in the ion?

3

Explanation:

A neutral atom has same number of protons and electrons. Ions dont have the same numbers, if a ion is negative it has more electrons than protons, if a ion is positive it has less electrons than protons.

Then a ion with a charge of positive one, 1 electron less than the number of protons. It has 4 protons so the number of electrons in the ion is 3

We identify an element from its atomic number = number of protons

So here the atomic number is 4 since it says 4 protons present.

The element is Berylllium, Be.

For a neutral atom atomic number = number of protons (positively charged) = number of electrons(negatively charged)

So the neutral atom contains 3 neutrons, 4 protons and 4 electrons.

Mass number = number of protons + neutrons

Since mass of an atom depends on the nucleus (protons and neutrons are present inside the nucleus)

Mass number = 3 + 4  

Mass number=7.

The ion has 1+ charge which means the neutral atom has lost 1 negative electron.

So The answer is  

Ion has 3 neutral neutrons

4 positive protons

3 negative electrons