how can we know how many electrons an atom has?


How did scientists count exact number of electrons, protons and neutrons of an atom?

How do we know that hydrogen has 1 electron and oxygen has 8 electrons?

Dont these numbers just represent some kind of **ratio** of charge or something?

Or is it exact integer value representing countable number of things in atom?

In: 0

Its the exact “integer” value of a charge, an electron does not have the charge of 1 so its not literaly an interger but all atoms cores and its shell have some integer multiple of that charge.

Back in the day, a scientist called Ernest Rutherford managed to strip apart the Hydrogen atom, and what he found at the center was a particle with a positive charge and almost all of the hydrogen atom’s mass, which he called the proton.

Through various experiments and calculations, it was determined that a proton and an electron have equal but opposite charge. Electrons also have a mass that is order of magnitudes smaller than a proton.

If you combine this knowledge with the concept that all atoms are electrically neutral, all you need to do to count the number of electrons is to count the number of protons.

This was done by another scientist, called Henry Moseley. He got atoms to shoot out x-rays and measured those rays to determine the number of protons an atom has.

As for neutrons, they are counted by simply subtracting the mass of the protons and electrons from the total mass of the atom and dividing that by the mass of a neutron, which was found by subtracting the mass of a normal hydrogen atom from the mass of a hydrogen atom with an extra neutron.

The number of protons must equal the number of electrons, so scientists counted the protons using x-rays. Neutrons were counted by looking at the mass that wasn’t accounted for by the protons and electrons.