Chemical bonding and the lewis structure

Chemical bonding and Lewis structure

A force that holds atoms together to

create a single unit.

Chemical bond

Metallic

Bonds

Metal + Metal

Covalent BondsNon-Metal + Non-Metal

Electrons are shared

between atoms.

Ionic Bond

sMetal +

Non-Metal

Electrons are

transferred.

Valence electrons• Electrons in the outer energy level of atom.• Are involved in chemical bonding.• Are easily removed.

Noble gases obey the octet structure.

Lewis Diagrams

SElectron pair Unpaired electron

When two non-metallic atoms bond together

by sharing one or more pairs of electrons.

Covalent bond

•Forms molecules.•Molecule is held together by a shared electron pair.• Individual atoms in the molecule has octet structure.

Covalent bond – single bond.

Covalent bond – single bond.

Covalent bond – double bond

Covalent bond – triple bond

Relative molecular mass is the sum of the relative atomic mass of

the atoms in the molecule.

Results from the transfer of one or more electrons from metal atoms to non-metal

atoms. Ionic bond

Metals give off electrons to form cations in order to obtain a noble gas electron structure.

Li Li+ + e-[He]2s1 [He]

[Ar]4s2 [Ar]Ca Ca2++2e-

Non-metals gain electrons to form anions in order to obtain a noble gas electron structure.

N + 3e- [ N ]3-[He]2s2p3

S + 2e- [ S ]2-[Ne]3s23p4

[He]2s22p6 = [Ne]

[Ne]3s23p6 = [Ar]

• The metal atom gives away its electrons to the non-metal.

• The positive and negative ions attract each other due to electrostatic forces.

(opposite charges attract)• The electrostatic attraction is the ionic

bond.• Crystal lattices form, and are built up of

alternating positive and negative ions.

Ca Ca2+ + 2e-

2x: F + e- [ F ]-

Ca2+ + 2[ F ]- Ca2+2[ F ]- CaF2

Positive ion:

Negative ion:

Crystal lattice

Now you do:Lithium Fluoride Li+ and F-

Aluminium sulfide Al3+ and S2-

Ionic compounds are in fact composed of many millions of ions, and not just one cation and one anion. This huge structure is known as a crystal lattice.

NaCl is the FORMULA unit (not a molecule of salt.)

Ionic bonds form between metals and radicals.

Radicals will also form ionic bonds with NH4

+

The sum of the relative atomic masses of the atom in the chemical

formula.Relative formula mass

Electrostatic attraction between the positive

atomic residue and the sea of delocalised

electrons. Metallic bonds

• Atoms have 1, 2, or 3 valence electrons.• Metallic atoms have a low ionisation energy.• Little energy required to remove valence

electrons – electrons delocalise.• Atoms are tightly packed to form a metal

lattice where the valence orbital overlap.• Atoms that lose an electron becomes positive

(called a positive atomic residue).• The bonding energy is the electrostatic force of

attraction between the sea of delocalised electrons, and the positive atomic residue.

Properties of metals

Reason

Metal glow Sea of delocalised electrons can reflect light and therefore causes the surface to shine.

Electrical conductor Sea of delocalised electrons can move freely and act as charge carriers.

Thermal conductor Sea of delocalised electrons act as carriers of heat energy (kinetic energy).

Malleable/Ductile Atoms, though firmly bound together, can slide over each other, allowing metal to bend and

stretch.High density Atoms in the solid phase is packed closely

together in a metal lattice.

Alloys

Metals are often converted into alloys to change their

properties. Alloys are usually always stronger than pure

metals.

Text: Olivier, A: Physical Science textbook and workbook, Grade 10 ; Reivilo Uitgewers.Slide 8 – 11: Lily KotzèSlide 18: Lily KotzèSlide 20: http://dtc-wsuv.org/isci/module/img/7_14_NaCl.png Slide 24: http://i.imgur.com/oIoEZhH.gif Slide 27: http://i0.wp.com/upload.wikimedia.org/wikipedia/commons/thumb/3/36/Alloy_Substitutional.svg/150px-Alloy_Substitutional.svg.png?w=625Slide 28: Steel: https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRb7xMBVsBuBLTvAOfjtLXoghcMRgMkIH5puPfnzKRRKmwUNtHk Stainless steel: http://curiousscience.com/images/stock/img780.jpg Bronze: https://upload.wikimedia.org/wikipedia/commons/c/ca/Apa_Schwerter.jpg