chapter 3 bonding

ionic bonding

ionic bonding

Ionic bonding involves electrostatic attraction between oppositely charged ions in a lattice. The formulas of compound ions, eg sulfate, hydroxide, nitrate, carbonate and ammonium.

simple covalent bond

A single covalent bond contains a shared pair of electrons.

dative covalent bond

bond contains a shared pair of electrons with both electrons supplied by one atom

metallic bonding

Metallic bonding involves attraction between delocalised electrons and positive ions arranged in a lattice.

physical properties of ionic bonding (4)

• brittle because once the lattice structure is disturbed ions with the same charge line up and repel each other

• solids at room temperature

• high melting points due to their large structures that require lots of energy to break the ionic bonds

• conduct electricity when molten or dissolved because the ions are free to move and carry current

physical properties of metallic bonding

• conduct electricity because they have a ‘sea’ of delocalised electrons

• conduct heat due to delocalised elctrons and the ions being closely packed

• malleable

• ductile

• high melting/boiling point

strength of a metallic bond depends on

the charge on the ion: greater charge→ more delocalised electrons → stronger electrostatic forces of attraction

the size of the ion: smaller the ion is the closer the electrons are to the nucleus

physical properties of gaint covalent/macromolecular bonding

• high melting and boining points

• solid at room temperature

• do not conduct heat

• do not conduct electricity

physical properties of simple covalent structures/ molecules

• low melting

• boiling points,

• low solubility

• are not good conductors of electricity.

diamond structure

tetrahedral with 1 carbon bonded to 4 other carbon atoms

graphite structure

hexagonal sheets with weak van der waal’s forces

1 carbon bonded to 3 other carbons

ice structure

regular lattice where the molecules become arranged into a 3D network where each water molecule is connected to four other water molecules by hydrogen bonds. As a result of this regular lattice structure, the water molecules in solid ice are further apart than the molecules in liquid water. The structure is more open in ice which makes it less dense than water.

iodine structure

diatomic molecule

Iodine has a simple molecular structure. Iodine atoms are bonded in pairs by covalent bonds, so the formula is I₂. In the solid state, the weak intermolecular forces between the iodine molecules hold them together in a 3D lattice structure. This is a simple molecular lattice.

magnesium structure

tightly packed lattice and exists as a large macromolecular structure (ie. a large interconnected lattice NOT molecules) with strong metallic bonds between the Magnesium ions and the sea of delocalised electrons.

sodium choride

a crystalline lattice structure, where each sodium ion is surrounded by six chloride ions and each chloride ion is surrounded by six sodium ions.

bonding pairs and how they react

Bonding pairs and lone (non-bonding) pairs of electrons as charge clouds that repel each other. Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repulsion.

stronger bond pairs?

Lone pair–lone pair repulsion> lone pair bond pair repulsion> bond pair–bond pair repulsion.

electro negativity

the power of an atom to attract the pair of electrons in a covalent bond.

trend going down group 1

Decreases because as you go down the group, the size of the ion increases, there is a weaker electrostatic force of attraction between the protons and delocalised electrons, thus requires less energy to break the forces. 

types of intermolecular forces

Van der Waals (London dispersion forces) 

Dipole - dipole 

Hydrogen bonding 

shapes of molecules and their bond angles

Linear – 180 

Trigonal planar – 120 

Tetrahedral 109.5 

Trigonal bipyramid – 90 & 120 

Octahedral - 90 

bond polarity in covalent bonds

elements with different electronegativities will make a compound with an unsymmetrical electron distribution. this makes a polar covalent bond creating a permanent dipole

why do some molecules with polar bonds do not have a permanent dipole

The presence of symmetrical bonds in a molecule means that the delta charges cancel each other out.

permanent dipole dipole

polar→ non polar strongest inetrmolecular force the attraction between two permanent dipoles

induced dipole dipole aka van der waal’s

non-polar and non-polar occurs exist between all atoms or molecules when the electrons are more on one side so a temporary slight charge occurs this depends on:

higher mass= stronger van der waal’s

more electrons: stronger forces

second strongest intermolecular force

hydrogen bonding

only occurs when nitrogen ocygen and fluorine react with hydrogen. this is the strongest type of intermolecular force due to it being highly polarised