SCIENCE CHEMISTRY

Atoms consist of electrons surrounding a nucleus that contains protons and neutrons.

Neutrons are neutral, electrons have a charge of -1 where as protons have a charge of +1

The number of protons in an atom is called its atomic number.

The electronic structure of an atom is a description of how the electrons are arranged

Both protons and electrons have an electrical charge. Both have the same size of electrical charge, but the proton is positive and the electron negative

-The total number of electrons in an atom is always the same as the number of protons in the nucleus. This means that atoms have no charge.

-The number of protons in an atom is called its atomic number

Ions are electrically charged particles formed when atoms lose or gain electrons.

Metal atoms form positive ions, while non-metal atoms form negative ions. 

The strong electrostatic forces of attraction between oppositely charged ions are called ionic bonds.

Ionic compounds have high melting and boiling points.

Ions are electrically charged particles formed when atoms lose or gain electrons.

-Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions.

-Non-metal atoms gain an electron, or electrons, from another atom to become negatively charged ions.

the number of charges on an ion formed by a metal is equal to the group number of the metal

the number of charges on an ion formed by a non-metal is equal to the group number minus eight

When metals react with non-metals, electrons are transferred from the metal atoms to the non-metal atoms, forming ions. The resulting compound is called an ionic compound.

There is a strong electrostatic force of attraction between oppositely charged ions, called an ionic bond.

A covalent bond is a strong bond between two non-metal atoms. It consists of a shared pair of electrons.

The electrons involved are in the outer shells of the atoms.

Covalent bonds are strong - a lot of energy is needed to break them. Substances with covalent bonds often form molecules with low melting and boiling points, such as hydrogen and water.

The number of covalent bonds is equal to eight minus the group number 

-molecules can have a double covalent bond - meaning they have two shared pairs of electrons.

They are shown with two lines:

E.g An oxygen atom consists of two oxygen atoms held together with a double bond.

-molecules can also have a triple covalent bond - meaning they have three shared pairs of electrons

They are shown with three lines:

E.g A molecule of Nitrogen has two nitrogen atoms held together by a triple bond.