C1 Unit 1 Fundamental Ideas

Atoms, elements and compounds

Elements=1 type of atom

Compounds=more than one type of atom

An atom has a tiny nucleus at its centre, containing protons and neutrons. This nucleus is surrounded by electrons.

Protons have a Positive charge (+1)

Electrons have a Negative charge (-1)

Neutrons are Neutral!

The number of electrons in an atom are equal and opposite to the number of protons in the nucleus, so atoms have no overall electrical charge.

Atomic Structure

The atomic number of an element = number of protons (number of electrons)

Mass number = number of protons+neutrons

i.e. Fluorine has an atomic number of 9 and a mass number of 19, so....

Electrons=9  Protons=9   and Neutrons=(19-9)=10

Atoms are arranged in the period table in order of their atomic number

The arrangement of electrons in atoms

The electrons in an atom are arranged in energy levels (or shells).

The first level…