Nature of substances and chemical reactions

Elements

Each element has its own symbol

Elements are made up of atoms

Each atom contains a nucleus

A nucleus is made up of two types of particles

Protons

positive charge

Neutrons

no charge

electrons

negatively charged and surround the nucleus

Every element's atom has their own certain amount of protons

The mass of an element is its relevant atomic mass

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Chemical formulae

Compounds

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All chemicals have a chemical symbol and formula

The chemical symbols have one or two letters

Chemical formulae for molecules indicates which elements are present and their amounts

A substance made of two or more elements chemically combined

A compound has different properties than the elements that went into it