bonding structure polarity

metallic solids

attractive force is metallic bonding, can be described as attraction between valence electrons and nuclei of neighbouring atoms. metallic bonding is strong and non-directional

ionic solids

oppositely charged ions are held together in a 3d lattice by strong electrostatic attraction known as ionic bonds

covalent network

special solids with unique structures and unexpected properties. atoms are held together by strong covalent bonds (diamond/graphite)

solubility

for a substance to dissolve the attraction between solute and solvent must be stronger than the attraction within solute. for molecules, like dissolved like. polar molecules dissolve in polar solvents (H2O) and non polar molecules dissolve in non polar solvents like cyclohexane. ionic substances will dissolve in water as the attraction between the ions and the polar water molecules is strong enough to overcome the ionic bond

ionic bonding

metal + non metal, involved the transfer of electrons. metals with lose electrons and form cations non metals will gain electrons and form anions

covalent bonding

between non-metal atoms, bonds found within molecules involves sharing of electrons

metallic bonding

can be described as the attraction between delocalised electrons and the nucleus of neighbouring metal atoms. metallic bonding is strong and non directional.

octet rule

applies to all atoms but H/B/Be. atoms are trying to acheive a full valence shell to become stable, for most its 8e-

VSEPR

valence shell electron pair repulsion. electron regions are. negatively charged and will arrange themselves as far apart as possible to minimise repulsion

base shape

determined by total number of electron regions around the central atom (also determines bond angle)

actual shape

determined by total number of bonding and non bonding regions

polarity

refers to uneven distribution of electrical charge within a molecule or chemical bond

explaining molecule shape

there are (how many) electron regions around the central (atom name) atom. these negatively charged electron regions arrange themselves in a (base shape) arrangement in order to maximise separation to minimise repulsion. the bond angle is (bond angle) (how many) of the bonding regions are bonding and (how many) are non bonding therefore the actual shape is (actual shape)

polar bonds

when a non metal bonds with a non metal, electrons are shared in a covalent bond. if electrons are not shared evenly a bond dipole forms where one atoms is slightly negative and the other is slightly positive. polar bond is a result of atoms with different electronegativity where one atoms has a greater attraction for electrons (more electronegative) than the other.

polar molecule

a polar molecule is one with a permanent dipole. for a molecule to be polar it must have bonsd dipoles that do no cancel. (tetrahedral and linear shapes are always non-polar because their bonds are pulling equally)

exothermic

heat energy released, products have less energy than reactants. negative enthalpy change and bonds are forming

endothermic

heat energy absorbed, products have more energy than reactants. positive enthalpy change with bonds breaking

delta r H

is the symbol for enthalpy change fr a reaction, measured in KjMolL-1

Delta r h equation

number of moles in problem divided by number of moles in equation Kj/Mol

delta h equation

mol x kj/mol

melting point

depends on the relative strength of the attractive force. strong attractive forces require a lot of heat energy to break bonds. weak attractive forces require very little heat.

electrical conductivity

requires free moving particles. ionic solids are made of positive and negative ions in a 3D lattice, in the solid state these ions are fixed and unable to move. therefore cannot conduct. however when ever molten or in solution the ions are free to move and can conduct electricity.

malleable

metals are malleable (can be hammered into shape- and ductile) becuase metals have strong non directional bonds, when force is applied the layers of atoms slide over each other without breaking the metallic bonds.

brittle

ionic solids are brittle.the ionic bonds in ionic solids are directional, when force is applied like charged ions line up and repel causing the ionic bonds to break and the ionic solid to shatter.