Chemistry flashcards (GCSE)

Element

A substance made up of identical atoms

Compound

2 or more (types of) elements chemically bonded together

Valency

A number given to an element within a chemical compound which means a combining power of that element

Molecule

2 or more atoms bonded together

Mixture

2 or more substances not chemically bonded

Relative atomic mass

The Ar of an element is an average value that takes account of the abundance of all the isotopes of an element

Isotopes

Atoms of the same element that have the same number of protons but a different number of neutrons

Period

A row in the periodic table, elements in the same period have the same number of energy levels

Electron shells

Energy levels

Group

A column in the periodic table, elements in the same group have the same number of electrons in the outer shell , this gives these elements similiar chemical properties

Atomic number

Number of protons in 1 atom (bottom number) + also the number of electrons

Mass number

Sum of protons neutrons in 1 from (top number)

Plum pudding model

The atom is a ball of positive charge with atoms embedded in it

Nuclear model

The mass of the atom was concentrated at the nucleus and that the nucleus was positively charged

Bohr model

Elections orbit the nucleus at specific distances (electron shells)

Protons and neutrons identified

The positive charge of any nucleus could be subdivided into sub-divided into smaller particles.

James Chadwick then provided experimental evidence to show the existence of neutrons within the nucleus.