Fundamental chemical concepts
A compound [compound: A compound is a substance formed by the chemical union (involving bond formation) of two or more elements. ] consists of two or more atoms from different elements chemically joined together. There are two types of chemical bond:
A covalent bond [covalent bond: A covalent bond between atoms forms when atoms share electrons to achieve a full outer shell of electrons. ] forms when two atoms share a pair of electrons. The atoms involved are non-metals such as carbon, oxygen and hydrogen. They join together to form molecules [molecule: A molecule is a collection of two or more atoms held together by chemical bonds. It is the smallest part of a substance that displays the properties of the substance. ].
The animation shows a covalent bond being formed between a hydrogen atom and a chlorine atom to form a molecule of hydrogen chloride:
Atoms can lose or gain electrons in chemical reactions. When they do this they form charged particles called ions [ions: Electrically charged particles, formed when an atom or molecule gains or loses electrons. ].
Ionic bonds are the forces of attraction between oppositely charged ions in a compound.
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