1. 04/01/12
EdExcel Additional Science
Chemical Structures
W Richards
The Weald School

2. Compounds
04/01/12
Compounds are formed
when two or more
elements are
chemically combined.
Some examples: Methane
Sodium
chloride (salt)
Glucose

3. Some simple compounds…
04/01/12
Carbon
Methane, CH4 Water, H2O dioxide, CO2
Key
Hydrogen
Oxygen
Ethyne, C2H2
Sulphuric Carbon
acid, H2SO4
Sulphur

4. Bonding Revision
04/01/12
Cl Hi. My name’s Johnny Chlorine.
I’m in Group 7, so I have 7
electrons in my outer shell
Cl
I’d quite like to have a full outer
shell. To do this I need to GAIN
an electron. Who can help me?

5. Ionic Bonding Revision
04/01/12
Cl Here comes my friend again,
Sophie Sodium Na
Hey Johnny. I’m in Group 1 so I have
one electron in my outer shell. Unlike
Harry, this electron is far away from
the nucleus so I’m quite happy to get
Okay rid of it. Do you want it?
- +
Cl Na
Now we’ve both got full outer shells
and we’ve both gained a charge.
We’ve formed an IONIC bond.

6. Covalent Bonding
04/01/12
Cl Here comes another one of my
friends, Harry Hydrogen
Hey Johnny. I’ve only got one
electron but it’s really close to H
my nucleus so I don’t want to lose
it. Fancy sharing?
Cl H
Now we’re both really stable.
We’ve formed a covalent bond.

7. Covalent bonding
04/01/12
Consider an atom of hydrogen:
Notice that hydrogen has just __ electron in its outer
shell. A full (inner) shell would have __ electrons, so two
hydrogen atoms get together and “_____” their electrons:
Now they both have a ____ outer shell and are
more _____. The formula for this molecule is H2.
When two or more atoms bond by sharing electrons we
call it ____________ BONDING. This type of bonding
normally occurs between _______ atoms. It causes the
atoms in a molecule to be held together very strongly
but there are ____ forces between individual molecules.
This is why covalently-bonded molecules have low melting
and boiling points (i.e. they are usually ____ or ______).
Words – gas, covalent, non-metal, 1, 2, liquid, share, full, weak, stable

8. Dot and Cross Diagrams
04/01/12
Water, H2O:
H
H O

9. Dot and Cross Diagrams
04/01/12
Oxygen, O2:
O O

10. Dot and cross diagrams
04/01/12
Water, H2O:
Step 1: Draw the atoms with Step 2: Put the atoms together and
their outer shell: check they all have a full outer shell:
H
O H O H
H
Oxygen, O2:
O O O O

11. Dot and cross diagrams
04/01/12
Nitrogen, N2: Methane CH4:
H
N N
H C H
H
Ammonia NH3: Carbon dioxide, CO2:
H N H
O C O
H

12. 04/01/12
Other ways of drawing covalent bonds
Consider ammonia (NH3):
H N H
H
H N H
H
H N H
H

13. Group 7 – The halogens
04/01/12
F
Cl
Br
I
At

14. The Halogens - Chlorine
04/01/12
Each molecule has a strong force
holding the atoms together, but
the forces between molecules are
very weak so chlorine is a gas at
room temperature

15. The Halogens - Bromine
04/01/12
The forces between molecules are
slightly stronger so bromine is a
liquid at room temperature.

16. The Halogens - Iodine
04/01/12
Iodine is a solid at room temperature but with gentle
heating it will melt. The atoms will remain in pairs.

17. Forms of Carbon
04/01/12
1) Diamond – very hard, doesn’t conduct
electricity, very high melting point
2) Graphite – soft, does conduct
electricity, very high melting point
3) Buckminsterfullerene – 60 carbon
atoms arranged in a sphere

18. Metals
04/01/12
+ + +
Metals are defined as elements that readily
lose electrons to form positive ions. There + + +
are a number of ways of drawing them:
+ + +
- - + + +
+ + +
-
- + +
+ +
-
-
+ + +
- + + +
-
Delocalised electrons

19. Nanoscience
04/01/12
Nanoscience is a new branch of science that refers to
structures built from a few hundred atoms and are
1-100nm big. They show different properties to the same
materials in bulk. They also have a large surface area to
volume ratio and their properties could lead to new
developments in computers, building materials etc.
Task: research nanoscience
and find two current and/or
future applications of this
science.

20. 04/01/12
Different ways of modelling atoms
H N H H N H
H H

21. Chemical-based Therapy
04/01/12
Chemical-based therapy is the use of chemicals to alleviate an
illness. Here are two examples:
Chemotherapy – drugs that are used to kill cancer cells
Antibiotics – drugs that are used to kill bacteria that cause
illnesses such as tuberculosis and cholera

22. Homeopathy
04/01/12
Homeopathic medicines are drugs that contain compounds
that, if strong enough, would cause an illness. These drugs
induce symptoms so that the body is “kick-started” into
starting the natural healing process.

23. Homeopathy
04/01/12
For Against
Homeopathy