Question

How many electron are in 56fe 3

Answer 1

The periodic table is arranged in a way so that with each step the number of protons in the nucleus is increased by 1. It makes it for an easy choice to designate elements with numbers - atomic numbers, because in that case atomic number shows the number of protons possessed by the nucleus. Like this:
H has 1 proton
He has 2 protons
Li has 3 protons
Be has 4 protons and so on

Each proton has a charge of +1. The other particle present in the nucleus - the neutron - has zero electrical charge and thus irrelevant when computing the charge of a nucleus. It is easy to deduce that the nucleus charge equals the number of protons (which in turn equals the atomic number). So the nucleus charges are:
for H it's+1
for He it's +2
for Li it's +3
for Be it's +4 and so on

Atom is an electroneutral particle by definition. It means it's summed charge must be 0. Since we've looked at everything within the nucleus (the protons and the neutrons) it's time we turn our gaze to the space around it, which is full of orbiting electrons. Each electron has a charge of -1. To make up for the positive charge in the nucleus you have to fill the space aroung the nucleus with negative electrons.Thanks to the elementary nature of both proton and electron charge, you simply have to take the same number of electrons as that of protons! Like this:
H has 1 proton and 1 electron
He has 2 protons and 2 electrons
Li has 3 protons and 3 electrons
Be has 4 protons and 4 electrons and so on

Fe has atomic number 26. It means that Fe has 26 protons and 26 electrons. If it's a neutral atom

You typed 3. Is it accidental? If so, then the answer is above. If not, then you could be trying to type 56Fe +3, which means an ionic iron with charge +3. Charges are formed when you have too many or too few electrons to counter-balance the prositive charge of the nucleus. Charge +3 means you're 3 electrons short to negate the nucleus positive charge.

In other words, Fe+3 has 26 protons and 23 electrons.