Ionic and covalent bonding

what are ionic bonds between?

metal and non-metal

why do ionic compounds have high melting and boiling points?

strong electrostatic attraction requires a lot of energy to overcome and break

what structure does ionic bonding have?

giant ionic lattice

what does melting point depend on?

• size of charge

• size of ions

how does solubility of ionic compounds differ?

decreases as ionic charge increases - attraction too strong for water to break down the lattice.

when does an ionic compound conduct electricity and why?

molten/in solution - ions are mobile

define covalent bond

strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms

what occurs when a covalent bond forms?

atomic orbitals overlap

what kind of attraction is a covalent bond?

localised

what do you do with lone pairs in displayed formulae?

draw them

which elements expand the octet?

phosphorus, chlorine, sulfur

why can some elements expand the octet?

the n=3 shell has a d-sub-shell available for the expansion

define dative covalent bond

a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only

how do you show a dative covalent bond in the displayed formula?

—> instead of a normal bond line

how to draw a molecule containing a dative covalent bond

draw the original molecule (will contain a lone pair)

donate 2 electrons from a single element

add the charge on the compound

what does average bond energy measure?

covalent bond strength

if the average bond enthalpy increases, what happens to the strength of the covalent bond?

increases

displayed formula NO_3^- ion

displayed formula CO_3^2- ion

displayed formula SO_4^2- ion

formula sulfite ion

SO_3^2-

formula manganate ion

MnO_4^-

Why do ionic compounds only conduct electricity when molten or in aqueous solution?

When solid, the ions are fixed in the giant ionic lattice and cannot move. In solution, ions are free to move and carry charge

An ionic compound has the empirical formula H4 N2 O3, suggest the formula of the ions present in this compound

NH4+ NO3-

What does isoelectronic mean?

Has the same number of electrons

what does the NH_4⁺ ion look like?

CO ion dot and cross diagram

Properties of ionic bonding

• high melting and boiling points

• Conduct electricity when aqueous or molten

• Brittle