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Covalent bonding
1. Covalent bonding
Sharing outside electrons
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2. Remember.
How many atoms in the following:-
Sulphuric acid H2SO4
2 Hydrogen 1 Sulphur 4 Oxygen
7 atoms; 3 different elements.
Sodium hydrogen carbonate NaHCO3
6 atoms; 4 different elements
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3. If both elements in a compound are
non-metals
Neither of them need to lose electrons.
Both of them need to gain electrons.
To fill both outer shells they must share.
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4. Hydrogen - 1H
Electronic structure 1 – each H needs 1 more
HH HH
Forming H2 molecules allows each Hydrogen
atom to have a share of a full outside shell
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5. Hydrogen formulae
The displayed formula of Hydrogen shows
the pair of electrons as a single bond.
H
H-H H
The molecular formula just counts the atoms
present
H2
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6. Chlorine Cl2
Electronic structure 2.8.7 – each needs 1 more
Forming Cl2 molecules allows each Chlorine
atom to have a share of a full outside shell
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8. Methane – CH4
6C (2.4) 1H (1)
Carbon needs 4 more electrons.
Each Hydrogen needs 1 more electron
H H
H
H
H C
H
H
H
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9. Methane
H
Displayed H
H-C-H
Formula
H
H
H C
Molecular H
CH4
Formula
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10. Water - H2O
8O (2.6) 1 H (1)
Oxygen needs to 2 more electrons
Each hydrogen needs 1 more electron
H
O
H
H H
Each Hydrogen has a share of 2 electrons; the Oxygen
has a share of 8
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11. Water
Displayed O
Formula H H
O
H
H
Molecular
H2O
Formula
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12. Oxygen
O (2.6)8
Both Oxygen atoms need to 2 more electrons
O O O O
Both oxygen share an outer shell of 8.
2 pairs of electrons are shared – a double bond.
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14. Carbon dioxide – CO2
6C (2.4) Carbon needs 4 more electrons
8O (2.6) Each Oxygen needs 2 more electrons
O O
C
O
O
All atoms have a share of 8 electrons in their outer shell.
Two double bonds O=C=O
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16. Consequences of Covalent
bonding.
There are no charged particles to move
about.
So covalent compounds are poor
conductors.
Molecules form that are only weakly
attracted to each other.
So boiling/melting points are low.
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17. Periodic Table
Elements in a group (column) share similar
chemical properties because they have similar
electronic structures
Group 1 0
Group 2 Group 3 4 5 6 7
Period 1
Period 2
Period 3
etc
Elements in
a row are
not similar
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18. Group 1
Each element
has the 1
electron in the
outer shell.
So group 1
elements react
in similar ways
19. Each group 0
Group 0 element has a
full outer shell.
So every element
has similar
properties.
Because each
outer shell is full
with different
numbers we say
the next shell
has 0 electrons
20. Period 3
Elements in period 3 have some electrons in the
first 3 shells and none in the fourth
21. Period 2
Each element has electrons in the first 2 shells.
Some need to gain electrons, some need to lose
electrons. Neon already has a full outer shell.
They behave differently
