chemistry

Building block of all matter. The smallest particle of a substance that can exist and still be that substance. Atoms are the fundamental units of matter.

Positively charged particle found in the nucleus of an atom. Protons determine the atomic number of an element.

Neutrally charged particle found in the nucleus of an atom. Neutrons contribute to the mass number of an atom.

Negatively charged particle found orbiting the nucleus of an atom. Electrons are involved in chemical bonding.

• Protons • Neutrons • Electrons These particles make up an atom.

Represents the number of protons in the nucleus. The atomic number defines the element.

Total number of protons and neutrons that are found in the nucleus of this atom. Mass number is used to identify isotopes.

Vertical column. Elements in the same column have the same number of valence electrons and therefore the same valency. Groups indicate similar chemical properties.

Horizontal row. Elements in the same row have the same number of electron shells. Periods indicate the energy levels of electrons.

Atoms of the same element (same number of protons) with different numbers of neutrons. Isotopes have the same atomic number but different mass numbers.

The arrangement of the electrons around the nucleus. Organised into shells or energy levels. Electron configuration determines an atom’s chemical properties.

The electrons in the outermost shell. Valence electrons are crucial for chemical bonding.

Atoms which have gained or lost electrons to have a complete valence shell (outermost shell) filled with electrons. Ions can be positively or negatively charged.

A positively charged ion (atom that has lost electrons). Cations are formed when an atom loses one or more electrons.

A negatively charged ion (atom that has gained electrons). Anions are formed when an atom gains one or more electrons.

Consist of only a single type of atom. Cannot be broken down into simpler substances by chemical means. Elements are the basic building blocks of matter.

Formed when two or more non-metallic atoms (same or different elements) are chemically joined together. Molecules can be simple or complex.

Contain two or more different elements that are chemically bonded together. These atoms are in a definite ratio. Compounds have unique properties different from their constituent elements.

A type of bonding that involves non-metals atoms only. Involves the sharing of electrons. Covalent bonds form molecules.

A type of bonding that involves both metal and non-metal atoms in the form of ions. Involves the transfer of electrons. Ionic bonds typically form between metals and non-metals.

The charge possessed by an atom. Valency indicates how an atom can bond with others.

When two solutions are mixed, an insoluble compound sometimes forms, that is a solid forms and separates from the solution. Precipitation reactions are common in chemistry.

Dissolves in water. Aqueous solutions are important in chemical reactions.

mass number - atomic number