4.1.1 A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

What is a compound?

Two or more elements chemically combined in fixed proportions

How are compounds formed?

By chemical reactions which always involve the formation of one or more new substances

What is a mixture?

Two or more elements not chemically combined together

How can mixtures be separated?

Filtration, crystallisation, simple distillation, fractional distillation, chromatography

What was the atom first believed to be?

Tiny spheres that could not be divided

What model and belief did the discovery of electrons lead to?

Plum pudding model - the atom is a ball of positive charge with negative electrons embedded in it

What was the alpha particle scattering experiment?

A beam of alpha particles was aimed at very thing gold foil. Some alpha particles emerged from the foil at different angles and some came straight back

What was the conclusion of the alpha particle scattering experiment?

The mass of an atom was concentrated at the centre and the nucleus was charged. The positively charged alpha particles were being repelled and deflected by a small concentration of positive charge in the atom

What did Bohr suggest about electrons?

They orbit the nucleus at specific distances

What did Chadwick provide evidence for?

The existence of neutrons within the nucleus

What is the atomic number?

The number of protons in an atom of an element

What is the mass number?

The sum of the prottons and neutrons in an atom

What is the relative charge and mass of a proton?

+1, 1

What is the relative charge and mass of a neutron?

0, 1

What is the relative charge and mass of an electron?

-1, very small

What are isotopes?

Atoms of the same element with different numbers of neutrons

What is the equation for relative atomic mass?

(Isotope 1 mass x abundance) + (Isotope 2 mass x abundance) divided by 100

What do electrons occupy in an atom?

The lowest available energy levels (the shells closest to the central nucleus)

What does the electronic structure of an atom tell you?

How many electrons are in each shell