C1 1.1: Atoms, elements and compounds
- 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.
C1 1.2: Atomic structure
- 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.
C1 1.3: The arrangment of electrons in atoms
- 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.
C1 1.4: Forming bonds
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.
C1 1.5: Chemical equations
- 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.