atomic structure and periodic table

What is an atom

A very small particle that makes up all of matter.

What is an element?

A substance made of only one type of atom

What is a compound?

A substance made from two or more different elements chemically bonded together in fixed proportions

How are elements represented?

Elements are represented by chemical symbols, e.g H for hydrogen

How are compounds represented?

Compounds are represented by chemical formulae showing the ratio of the atoms, e.g H₂O

What is a word equation?

A word equations shows reactants and products using words

Why can compounds only be separated by chemical reactions?

Because the elements in the compound are chemically bonded together

What are the state symbols and what do they mean?

(s) solid, (l) liquid, (g) gas, (aq) dissolved in water

What are ionic half equations used for?

They show how electrons are transferred in reactions involving ions

What is a mixture?

A mixture contains two or more substances that are not chemically bonded

Name physical separation techniques.

Filtration, crystallisation, simple distillation, fractional distillation, chromatography.

How does filtration work?

It separates an insoluble solid from a liquid using filter paper.

What is crystallisation?

It separated a dissolved solid by evaporating some solvent so crystals form

What is simple distillation used for?

Separating a liquid from a solution by boiling and condensing the liquid

What is fractional distillation used for?

Separating liquids with different boiling points.

How does chromatography work?

Substances move at different speeds due to different solubilities and attractions.

What was daltons model of the atom?

Atoms were solid, indivisible spheres

What did the discovery of the electron show?

Atoms are not solid ; they have internal structure

What is the plum pudding model?

A model with a positive sphere of charge with negative electrons embedded into it

What was the alpha- particle scattering experiment ?

Alpha particles ere fired at gold foil to test atomic structure