What matter is in an element?

Answer 1

The only matter in a stable element is at least one of each of the two stable electrically charged subatomic particles, protons and electrons, and except for an atom of the isotope hydrogen-1, at least one neutron, the uncharged stable subatomic particle. The numbers of protons and electrons must be the same. Artificial elements may contain other subatomic particles such as positrons.

(The subatomic particles themselves are considered to be composed of quarks, which could be called sub-subatomic particles, but quarks are not usually considered to be matter since they can not exist in isolation for more than very small fractions of a second.)

Answer 2

An element is made up of only one type of atom. Atoms are composed of three fundamental particles: protons, neutrons, and electrons. The specific arrangement and quantity of these particles determine the properties of the element.