Atomic Structure (1c)

Unit 1, Principles of Chemistry: Part 1, c

Atom

The smallest particle of an element that contains electrons surrounding a nucleus containing electrons and protons

Molecule

A group of tow or more atoms chemically combined to form an identifiable unit which retains the properties and composition of the substance

Subatomic Particle Masses

• Protons: 1

• Electrons: 1/1840

• Neutrons: 1

Atomic Number

number of proton in the nucleus of an atom

Mass number

number of neutrons and protons in the nucleus

Isotope

atoms of the same element, with the same number of protons but different number of protons

Relative atomic mass

The average mass of an atom of an element, taking into account the abundance of all its isotopes. With reference to 1/12th the mass of Carbon-12

Relative Atomic Mass formula

(% of isotope A x mass of isotope A) + (% of isotope B x mass of isotope B) / 100