7. Metal and Non-metals
ELECTRONIC NATURE OF METALS AND NON METALS
THE ESSENTIAL DIFFERENCE BETWEEN METAL AND NON METAL IS
THEIR AFFINITY FOR ELECTRONS.
A METAL IS AN ELEMENT WHICH BECOMES POSITIVELY CHARGE
WHEN IT LOSES ELECTRONS.
A NON METAL IS AN ELEMENT WHICH FORMS
NEGATIVE IONS BY GAINING ELECTRONS.
COMPARE THE ELECTRONIC CONFIGURATION OF METALS AND NON
METALS WITH THOSE OF NOBLE GASES
Non-metals Noble gases Metals
O 2:6
Ne 2:8
F 2:7
Ar 2:8
S 2:8:6
Cl2:8:7
Na 2:8:1
Mg 2:8:2
K 2:8:8:1
Ca 2:8:8:2
8. 11/05/14
8
cont…
Most metals have 1-3 electrons more than a noble gas
and non metals have 1-4 electrons less than noble gas.
Metal therefore reacts by electron loss forming an ionic
compound,
Non-metal combine either by electrons gain forming
ionic compound or by sharing electrons forming covalent
compounds.
9. 11/05/14
9 cont..
Physical properties of metals and non metals
Metals Non metals
Lustrous; Can be polished Not lustrous Cannot be polished
Maleable i.e. can be made in sheet Not maleable
Sonorous i.e. makes sound when heat Not sonorous
Ductile i.e. can be drawn in wire Not ductile
Good conductor of heat and electricity Poor conductors
High tensile strong and tough Low tensile
High density Low density
Solids with high melting points About half are gases, solids have low
melting points.
10. 11/05/14
10
cont…
Exceptional physical characteristics
Mercury is a liquid metal (MP-39ºC)
Metal Na and K have low densities and float on water,
their melting point are low Na 98ºC, K 63ºC and they are
soft enough to be cut by knife.
The non-metal carbons has high M.P about 3700ºC and
its allotropies shiny, solid and good conductors of
electricity.
11. 11/05/14
11
Oxides. Metallic oxide are ionic and contain oxide ions
O2- formed by transfer of electrons from metal to oxygen.
They are basic oxides and some (e.g. Na2O, CaO, MgO)
react with water to form alkalis.
No-metalic oxides are covalent and do not contain oxide
ions. Usually they are acid anhydrides:
CO2 +H2O ↔ H2CO3 ↔ 2H+ +CO3
2-
A few non metallic oxide are neutral.(CO,N2O, NO)
12. 11/05/14
1 2 cont..
Chemical characteristic of metal and non
metals.
Metals Non metals
Oxides are basic Oxides are acidic
Displace hydrogen from acid Do not melt with dilute acids
Chlorides are ionic Chlorides are covalent
They are reducing agent They are oxidizing agent
Do not usually combine with hydrogen. Forms stable hydrides with hydrogen
13. 11/05/14
13
Action on dilute acids:
Acids contains hydrogen ions H+. Metal can transfer electrons to these ions forming
hydrogen and metallic ions.
Zn + 2H+ _____Zn2++ H2 Metals below hydrogen in reactivity series. (e.g. Cu, Hg)
can not do this.
Non metals can not transfer electrons to hydrogen ions, they form ions by gaining
electrons.
Combination with hydrogen:
Non metal can reach the noble gas configuration by sharing electrons they do this
with hydrogen and form stable hydrides, e.g. H2S, NH3
Metals tend to loose and not to share electrons and therefore rarely form hydrides.
The very electropositive metals (K, Na, Ca) lose electron so easily that they can
transfer them to hydrogen and forms hydrides (KH, NaH, CaH2). In these hydrogen
is a negative ion. i.e. form anode when molten hydride electrolyzed.
14. 11/05/14
14
Chlorides:
The chlorine atoms(2:8:7) needs 1electron to complete its
outer octet. Metal atoms transfer electrons to chlorine
atoms and forms ionic chlorides:
Na + Cl → (Na+ +Cl-)
2.8.1 2.8.7 2.8 2.8.8
Non metals share electrons with chlorine, and form ionic
chlorides which are hydrolyzed by water. PCl3 + 3H2O →
3HCl + H3PO3, phosphonic acid.
