Chemistry - Chapter 2 - Atoms, Elements and Compounds

Atom

the smallest part of an element that can exist in a stable entity

Ion

a species with a positive (cation) or negative (anion) charge

Element

a substance that is made of the same type of atoms that cannot be split up by chemical means

Compound

a pure substance, which contains two or more different elements

Molecule

the smallest part of an element or a compound, which can exist alone under ordinary conditions

Mixture

two or more substances that can be separated by physical means

Proton (atomic) number

equal to the number of protons in the nucleus of an atom

Mass (nucleon) number

equal to the total number of protons and neutrons in the nucleus of an atom

Isotopes

atoms of the same element, with the same number of protons but different neutron number

Ionic bond

strong electrostatic attraction between oppositely charged ions

Ionic lattice

a giant structure of ionic compounds with a regular arrangement of alternating positive and negative ions

Covalent bond

formed when a pair of electrons is shared between atoms leading to noble gas electronic configurations.

Simple molecular

a molecule that is made from a small number of atoms

Macromolecule

consists of a large number of atoms bonded together to form one molecule with a very high relative molecular mass

Allotropes

different crystalline forms of the same element. They have the same chemical properties but different physical properties

Metallic bond

an electrostatic attraction between the positive ions in a giant metallic lattice and a ‘sea’ of delocalised electrons

Physical property

something about the appearance or state of a material

Chemical property

something about the chemistry of a material

Alloy

a mixture that contains at least one metal