1.1A Elements, Compounds and Mixtures

Elements

A chemical element is a single pure substance, made of only one type of atom.

• Atoms of an element are all the same as each other (except for isotopes)

• Atoms of an element are different than atoms of another element

• Each element is denoted by a chemical symbol

e. g. Gold = Au

An atom is the smallest particle of an element to show the characteristic properties of that element.

• Distinct nature of atoms gives each element individual properties

• Some elements are found in their native form in nature, uncombined with other elements

Compounds

Other elements are found as compounds, chemical combinations of different elements

• Compounds contain fixed proportions/ratios of elements, held together by chemical bonds

• Physical and chemical properties of compounds are different than those of the elements they contain (the bonding between atoms changes properties)

e.g. Na Cl₂ NaCl

Reactive Toxic Edible

Metal Gas Solid

Mixtures

A mixture is composed of two or more substances in which no chemical combination has occurred

• Components have different physical and chemical properties

• Composition of mixture is not fixed

Homogenous

Uniform composition and properties

• If you take a sample from anywhere in the mixture, you would have the same properties

Heterogenous Mixtures

Non-uniform composition, properties are not the same throughout

It is usually possible to separate components of heterogenous mixtures

Methods of Separating Components

Filtration: process in which solid particles in a liquid are removed through the use of a filter that allows the fluid to pass through but not the solid

Recrystallization: a substance is separated from others by dissolving the mixture in a solvent and then crystalizing the desired substance from the solution

Distillation: components of a liquid mixture are separated through selective boiling and condensation

Paper Chromatography: separates components of a mixture based on adsorption to a solid phase