Atomic Structure and The Periodic Table

Question 1

Atoms

Answer 1

All substances are made of atoms. An atom is the smallest part of an element that can exist.
Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium.

Question 2

Elements and the periodic table

Answer 2

An element is a substance with only one type of atom. Elements are listed in the periodic table. There are about 100 different elements. Elements can be classified as metal or non-metal depending on their properties. The columns in the periodic table are called groups and contain similar elements. The rows in the periodic table are called periods. Elements show a gradual change in properties across a period.

Question 3

Compounds

Answer 3

Some elements combine through chemical
reactions to form compounds. Compounds are made from two or more different elements (types of atoms) combined together in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed, e.g CO2. Compounds have different properties from the elements they are made from. Compounds can only be separated into elements by chemical reactions.

Question 4

Mixtures

Answer 4

A mixture consists of two or more elements or compounds not chemically combined together.
The chemical properties of each substance in the mixture are unchanged.

Question 5

Separating Techniques

Answer 5

Mixtures can be separated by physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography. These physical processes do not involve chemical reactions.