Chemical bonding

ionic, covalent, metallic

the attraction between oppositely charged ions or metals and non- metals

covalent bonding involves 2 non-metal atoms sharing one or more pairs of electrons - positively charged nuclei are attracted to the shared pair of electrons by electrostatic forces, making these bonds very strong

the attraction between positively charged ions aand negatively charged delocalized electrons

in mixtures of metals and alloys

-cations are positive ions -these are created when an atom loses electrons -the metals in group 1 and 2 can easily lose electrons to be cations

-anions are negatively charged ions -created when an atom gains electrons -The non-metals in Group 7 are most likely to gain electrons to fill up their electron shell and become negatively charged.

giant structures that are held together by strong electrostatic forces between the positive and negative ions

charged particles

so that they become stable

advantages - useful in showing how ionic compounds are formed, how the electrons move disadvantages - they don’t show the size of the ions, the structure of the compound or the way the ions are arranged - doesnt show the forces between the ions

• very high melting points because of the strong electrostatic forces in between the ions, a lot of thermal energy required to break • when they’re solid, cannot conduct electricity, can only conduct electricity in molten form or dissolved in water, when they are in these forms, the ions are free to move and carry charge

advantages - shows the regular pattern of an ionic crystal - shows how all the ions are arranged - suggests that the crystal extends beyond whats shown in the diagram disadvantages - we can’t see the forces in between the ions - not to scale

between two non metals e.g H2O or between non-metal elements like Mg2

substances made up of molecules containing a few atoms joined together by covalent bonds

H2 CL2 O2 N2 H2O CH4

• atoms within the molecules held together by very strong covalent bonds • the forces of attraction between the molecules are very weak • to melt a simple molecular substance, only need to break weak intermolecular bonds, melting and boiling points very low as the molecules are easily parted • as molecules get bigger, strength of intermolecular increases, therefore melting and boiling points increase • they don’t conduct electricity as they aren’t charged, so there are no free electrons or ions

• involves delocalized electrons • the electrons in the outer shells of metal atoms are delocalized ( free to move around ) , there are strong electrostatic forces between the positive ion and shared electrons. • these forces of attraction hold the atoms together in a regular structure

• in metallic elements • in metal alloys

• strong • high melting and boiling points • most are malleable • most are solid at room temp

• pure metals are often too soft, mixed with other metals to give them different properties like hardness • mixing elements with pure metals will distort the layers of the metal atoms, making it harder for the metal atoms to slide over each other, increasing hardness again

a giant structure of ions

because the delocalized electron in the metal carry electrical charge through the metal, energy in transferred by the delocalized electrons

because the electrostatic forces between the metal atoms and delocalized electron are very strong, needs a lot of energy to break