Bonding

What do you know about bonding?

Learning Objectives

• Define Key terms.

• Describe Ionic Bonding

• Construct Dot/Cross diagrams for ionic compounds.

Match upIonic Bonding Formed when atoms of

different elements chemically bond together

Covalent Bonding Generally a metal bonded to a non metal. Electrons are transferred, and ions are formed.

Metallic bonding. Electrons are shared between all the atoms (delocalised outer electrons)

Compound Electrons are shared between 2 non metals

Now look in your book for a copy of the ‘definition’ what do you think the key parts are??

Ionic Bonds

• Electrons are transferred from the metal atom to the non metal atom.

• Oppositely charged ions are formed which are held together by electrostatic attraction.

• A giant ionic lattice is formed.

THE IONIC BONDTHE IONIC BOND

Ionic bonds tend to be formed between elements whose atoms need to “lose” electrons to gain the nearest noble gas electronic configuration (n.g.e.c.) and those which need to gain electrons. The electrons are transferred from one atom to the other.

Sodium Chloride

Na 1s2 2s2 2p6 3s1 Na+ 1s2 2s2 2p6

Cl 1s2 2s2 2p6 3s2 3p5 Cl¯1s2 2s2 2p6 3s2 3p6

An electron is transferred from the 3s orbital of sodium to the 3p orbital of chlorine; both species end up with the electronic configuration of the nearest noble gas the resulting ions are held together in a crystal lattice by electrostatic attraction.

_

Half equations and electron configurationsHalf equations and electron configurations

Na ——> Na+ + e¯ 1s2 2s2 2p6 3s1 1s2 2s2 2p6

Cl + e¯ ——> Cl¯ 1s2 2s2 2p6 3s2 3p5 1s2 2s2 2p6 3s2 3p6

ELECTRON

TRANSFER

Mg ——> Mg2+ + 2e¯ and 2Cl + 2e¯ ——> 2 Cl¯

Mg

Cl

Cl

e¯

e¯

THE IONIC BONDTHE IONIC BOND

FORMATION OF MAGNESIUM CHLORIDE

What would the electron configurations be? For all species? (4 of them)

Draw your own diagrams with electron configurations and half equations for:

Calcium oxide (CaO), Sodium Oxide (Na2O) and Aluminium Fluoride (AlF3)

This question is about different models of bonding and molecular shapes.

Magnesium sulfide shows ionic bonding.(i) What is meant by the term ionic bonding?..................................................................................................................................................................................................................................................[1] (ii) Draw a ‘dot-and-cross’ diagram to show the bonding in magnesium sulfide. Show outer electron shells only.  

Ionic bonding and the periodic table

• 1. Drawn a dot/cross diagram (outer shell) for a) MgO, b) CaBr2, c) Na3P, d) Al2O3

• 2. Write out the electron configuration for K and K+, S and S2-

Learning Objectives

• State common molecular ions

• Be able to predict ionic charge

• Apply to exam questions

Notes

• In general:• Group 1-3 lose elctrons to form the configuartion of PREVIOUS

noble gas.• Group 5-7 gain electrons to form the configuration of the NEXT

noble gas.

• Be, C, B and Si don’t tend to form ions due to too much energy being required to remove electrons.

• Transistion Metals: • Iron (II) Fe 2+ Iron (III) Fe 3+

• Copper (I) Cu+ Copper (II) Cu 2+ (Just look at the roman numerals)

Ions formed

1 2 3 4 5 6 7

Atom Li Be B C N O F

Ion

Atom Na Mg Al Si P S Cl

Ion

Atom K Ca Br

Ion

Molecular Ions

• Some such as NH4+ and OH- can be worked out.

• Others such as sulphate, think about what the acid would be.•

1+ 1- 2- 3-Ammonium NH4

+

Hydroxide OH- Carbonate CO32- Phosphate PO4

3-

Nitrate NO3- SulphateSO42-

Nitrite NO2- Sulphite SO32-

Hydrogen Carbonate HCO3

-

Dichromate Cr2O7

2-

Working out ionic formulae

Calcium Chloride

Atom Ion Charge Ratio

Ca Ca2+ 2+ 1

Cl Cl- - 2

= CaCl2

Questions

Lithium Nitride

Calcium Iodide

Aluminium Sulphide

Magnesium Phosphide

Nickel (II) Chloride

Copper(I) Oxide

Iron (III) Chloride

Titanium (IV) Chloride

Aluminium Sulpahte

Calcium Hydroxide

Iron (III) Sulphite

Chronium (III) Nitrite

Manganese (VI) Oxide

Chromium (III) Oxide

Ammonium Phosphate

Sodium Dichromate

Apply to exam question