3.1.3.1 ionic bonding

what is ionic bonding?

the strong electrostatic force of attraction between the oppositely charged ions in a lattice

explain what will happen to metals during ionic bonding

• metals lose electrons when bonded to non-metals in order to achieve the nearest noble gas electronic configuration

• the metal is left as a positive ion

explain what will happen to non-metals during ionic bonding

• non-metals gain electrons in order to achieve the nearest noble gas electronic configuration

• the non-metal is left as a negative ion

in ionic bonding, the metal _______ its electrons to the non-metal which results in what?

• transfers

• so the stability of each atom has now increased

• there is now a strong electrostatic force of attraction between the oppositely charged ions

draw a dot + cross diagram for NaF

*outer shells are only shown

however the + and - charges do not just point in one direction, explain what they do instead + what this results in

• they span out to create a giant 3D structure where there is a constant state of repulsion between ions with the same charge + attraction between ions of opposite charge

• as a result, all the different forces find a balance as the ions form a giant ionic lattice

draw the structure of a general giant ionic lattice

eg for NaF

give 3 properties of ionic compounds

1. they are always solids at room temperatures

2. they will not conduct electricity in the solid state but will in the molten state

3. they are brittle + will shatter upon impact

explain why ionic compounds are solids at room temp

• they have a giant ionic lattice structure + their melting + boiling points are very high

• this is due to the strong electrostatic attraction between the oppositely charged ions

• so lots of energy is required to overcome the forces

explain why ionic compounds will not conduct electricity in the solid state but will when molten

• solid → ions are not free to move or flow so cannot carry a charge

• when molten or dissolved in water → ions are free to move/flow so are able to carry a charge

why are ionic compounds brittle + will shatter upon impact?

upon impact, the like charges will line up + repel, this repulsion results in the shattering

give 2 factors that increase the strength of ionic bonds

• the greater the ion charge, the stronger the bond

• the smaller the ionic radius, the stronger the bond

state which groups in the periodic table with become cations and which will become anions when reacting

groups 1, 2, 3 → form cations (+, +2, +3)

groups 5, 6, 7 → form anions (-3, -2, -)

(the charge is determined from which group the element is in)

which groups will not tend to form ions and why?

groups 4 + 8

• elements in group 8 are energetically stable, they have fully filled shells/orbitals

• elements in group 4 do not because they would have to either lose 4 electrons or gain 4 → they are relatively stable

what type of ions do the transition metals form?

atoms of these elements can lose different numbers of electrons depending on what they are bonding to and what the environment is → so they can form a variety of ions

what tells us the charge on the ions of transition metals?

these ions will have a roman numeral after the name eg iron(III) showing us that its Fe³⁺

how do you construct formulas for ionic compounds?

you have to balance the charges of the cation and the anion so the negative + positive charges cancel out

• eg magnesium chloride → Mg²⁺ Cl⁻

  therefore 2 CL are needed to balance the Mg charge

an easier way to do is is to just swap the charges over

give the formulas of the compound ions: hydroxide, nitrate, carbonate, sulfate + ammonium

hydroxide → OH⁻

nitrate → NO₃⁻

carbonate → CO₃²⁻

sulfate → SO₄²⁻

ammonium → NH₄⁺