Chemistry - Atoms

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Atoms

All atoms are made up of protons, neutrons and electrons.

Mass number - the number of protons + neutrons

Atomic number - the number of protons in the nucleus

Isotope - an element with the same number of protons but a different number of neutrons

The number and arrangement of electrons that decides the chemical properties of an element, isotope have the same electron configuration thus the same chemical properties.

However isotopes of an element do have slightly different physical properties such as density and rate of diffusion.

Relative mass

The relative atomic mass is the average mass of an atom of an element relative to 1/12 of carbon 12

The relative isotopic mass is the mass of an atom of an isotope of an element relative to 1/12 of carbon 12

The relative molecular mass is the average mass of a molecule relative to 1/12 of carbon 12