Describing MatterElements

What is an element?Element: Is a pure substance that cannot be

broken down into other substances by chemical or physical means.

Gold( Au) Silver(AG)

Elements are the simplest of substances

It is made up of only one kind of atom. (EG) Aluminum, Zinc & Copper (Pennies)

Nitrogen, Oxygen, & Hydrogen

Can be identified by its chemical and physical properties

Particles of Elements-Atoms Atom: Is the basic particle from which all

elements are made.

Made up of protons, neutrons, and electrons

Different elements have different atoms, henceforth, different properties

Lead(Pb) Oxygen(O)

(EG) Carbon: A carbon atom has a positively charged center, or nucleus, that contains smaller particles; a cloud of negative charge surrounds it. Fig 5 p. 39

When atoms CombineChemical bonds: When atoms combine

Water

Molecules: Groups of two or more atoms held together by chemical bonds

(EG) Water: A molecule of water consists of an oxyge

atom chemically bonded to two hydrogen atoms.

Two atoms of the same element can also combine to form a molecule

(EG) Oxygen molecules consist of two oxygen atoms

O₂ O₃

Ionic Bond forms by attraction of opposite charges of valance electrons

NaCl: salt

Covalent Bond forms by sharing of valance electrons

N₂

More examples

CompoundsCompound: Is a pure substance made of two

or more elements chemically combined in a set ratio

Chemical formula: shows the elements in the compound and the ratio of atoms

When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements

Carbon Dioxide: Its chemical formula is CO2. The number 2 below the oxygen tells you the ratio of carbon to oxygen, 2 to 1 (If there is no number after the symbol, the number 1 is understood).

Different ratios mean different compounds (EG) CO