Atomic Structure

Protons, electrons, neutrons.

particle	relative charge	relative mass
electron	-1	negligible mass
proton	+1	1 atomic mass unit
neutron	0	1 atomic mass unit

 

Isotopes

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons. Their chemical reactions are the same, physical properties different such as density.

The nucleon number(A) is the sum of protons and neutrons in the nucleus

The proton number (Z) is the number of protons in the nucleus.

Atomic mass units and relative isotopic mass.

1 a.m.u is equal to one-twelfth the mass of a ¹²C atom.

Relative isotopic mass is the mass of an atom of an individual isotope, relative to one-twelfth the mass of a ¹²C atom.

Relative atomic mass is the average mass of an atom, taking the natural abundances

of its isotopes into account, relative to one-twelfth the mass of a ¹²C atom.

Relative molecular mass is the mass of a molecule of an element or compound, relative to one-twelfth the mass of a ¹²C atom.