C2

• ions are made when electrons are transferred
• ions are charged particles and can be single atoms or groups of atoms
• when atoms lose or gain electrons to form ions, they are trying to get a full outer shell like a noble gas (a stable electronic structure).
• atoms with full outer shells are very stable
• when metals form ions, they lose electrons from their outer shell to form positive ions
• when non-metals form ions, they gain electrons into their outer shell to form negative ions
• the number of electrons lost or gained is the same as the charge on the ion. E.g. if 2 electrons are lost the charge is 2+, if 3 electrons are gained the charge is -3
• when a metal and a non-metal react together, the metal atom loses electrons to form a positively charged ion and a non-metal gains these electrons to form a negatively charged ion.
• oppositely charged ions are strongly attracted to each other by electrostatic forces. This attraction is called an ionic bond.
• oppositely charged ions are strongly attracted to each other by electrostatic forces. This attraction is called an ionic bond.
• ionic bonds are between metals and non-metals
• group 1 and 2 elements are metals and they lose electrons to form positive ions
• group 6 and 7 are non-metals, they gain electrons to form negative ions
• elements in the same group all have the same number of outer electrons. So they have to lose or gain the same number to get a full outer shell, this means that they form ions with the same charges
• groups 1&2 and 6&7 are the most likely to form ions
• a sodium atom is in group 1 so it loses 1 electron to form a sodium ion with the same electronic structure of neon
• group 1 elements form 1+ ions
• group 2 elements form 2+ ions
• group 2 elements form 2- ions
• group 7 elements form 1- ions
• dot and cross diagrams show how ionic bonds are formed
• ionic compounds have a regular lattice structure (giant ionic lattice)
• the ions in an ionic compound form a closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between oppositely charged ions, in all directions in the lattice
• a single crystal of sodium chloride (table salt) is one giant ionic lattice
• lattices can be presented as a ball and stick model or a regular model
• ionic compounds have high melting points and high boiling points due to the many strong bonds between the ions, it takes lots of energy to overcome this attraction
• ionic compounds can not conduct electricity when they're solid as they are held in place
• when ionic compounds melt, the ions are free to move and they'll carry electric charge
• some ionic compounds dissolve easily in water. the ions separate and are all free to move in the solution, so they'll carry electric charge
• if there is a dot and cross diagram of an ionic compound, count up how many atoms there are of each element and write this down to give you the empirical formula
• if you are given a 3D diagram of the ionic lattice of an ionic compound, use it to work out what ions are in the ionic compound, you'll then have to balance the charges of the ions so that the overall charge on the compound is zero
• when non-metal atoms bond together, they share pairs of electrons to make covalent bonds.
• the positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces, making covalent bonds very strong.
• atoms only share electrons in their outer shells (highest energy levels)
• each single covalent bond provides one extra shared electron for each atom
• each atom involved generally makes enough covalent bonds to fill up its outer shell. Having a full outer shell gives them the electronic structure of a noble gas, which is very stable. (covalent bonding)
• covalent bonding happens in compounds of non-metals and in non-metal elements
• dot and cross diagrams are useful for presenting which atoms the electrons in a covalent bond come from. Electrons drawn in the overlap between the outer orbitals of two atoms are shared between those atoms
• 3D models of covalent bonding are useful because it shows the atoms, covalent bonds and their arrangement
• simple molecular substances are made up of molecules containing a few atoms joined together by covalent bonds