C1 Unit 1 Chemistry: Fundamental ideas

• Substances that are made up of only type of atom are called element.
• Elements in the periodioc table are arranged in columns which are called groups, groups contain elements with similar chemical proporties.
• Compunds conatain more trhan one type of atom chemically bonded together.
• An atom has a tiny nucleus in its centre which is surrounded by electrons.

• The nucleus of an atom contains protons and neutrons and electrons orbit the nucleus.
• The number of electrons and protons in any atom is equal.
• Neutrons have no charge so the nucleus overall has a positive since the charge on a proton is +1.
• The charge on an electron is -1.
• Overall an atom is neutral since the charges of the electrons and the protons cancel out.
• The number of protons in each atom is called the atomic number.
• The mass number is the number of protons plus the number of neutrons.
• Number of neutrons=mass number - atomic number.

• The chemical proporties of elements depend on how many electrons they have.
• How reactive the an element is depends on how many electrons it contains in its outer shell.
• Elements in group 0 are called noble gases because they are unreactive and have a full outer shell.

Some atoms react by transferring electrons to form bonds, this happens when metals react with non-metals .

If the atoms that are reacting are both non-metal they share electrons to form chemical bonds.

When metals and non-metals react metals form positiviely charged ions and the non-metal forms negatively charged atoms.

Ionic bonds are the strong forces of attraction between positively and negatively charged ions.

Non-metals share electrons and react to form covalent bonds.

• No atoms are destroyed or created in a chemical reaction so the the total mass before the reaction is the same as the total mass after the reactions.
• There is the same number of each type of atom on each side of a balanced symbol equation.