Question - how many protons?
Question
Question
A helium nucleus 4He has 2 neutrons. How many protons are there?
The number of protons + neutrons A = 4.
If the number of neutrons N is 2 then there must be 4 - 2 = 2 protons.
There are 2 protons in the helium nucleus.
Ions
Normally, All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. are neutral.
They have the same number of protons in the nucleus as they have electrons orbiting in the energy levels around the The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei..
Atoms can, however, lose or gain electrons due to collisions or other interactions such as rubbing a material with a cloth.
When they do, they form charged particles called Electrically charged particle, formed when an atom or molecule gains or loses electrons.:
- if the atom loses one or more electrons, it will have more protons than electrons and so it becomes a positively-charged ion;
- if the atom gains one or more electrons, it will have more electrons than protons and so it becomes a negatively-charged ion;
- the atom will not normally gain or lose protons due to collisions or other interactions because they are held very tightly inside the nucleus. Electrons are much more loosely held.
A helium atom has two electrons in an energy level outside the nucleus.
The atom is neutral as it has two positive protons and two negative electrons.
A helium atom that has lost or gained an electron is a helium ion.
The ion has two positive protons but one electron so it is a positive ion:
The ion has two positive protons but three electrons so it is a negative ion: