atomic structure and bonding

1. Good Morning
&
Welcome

2. What and When
• Term 1 ( Sept – Dec)
– Unit 2, 5, 19, 3
• Term 2 (Jan – March)
– Unit 6, 12, 4, 7
• Term 3 (April – Jun)
– Unit 7, 16, 22

3. Unit 2 – Chemistry and our universe

4. Unit Content
Learning aim A: Investigate chemical reactivity and bonding
Learning aim B: Investigate how the uses of chemical
substances depend on their chemical and physical properties
Learning aim C: Investigate the factors involved in the rate of
chemical reactions.
Learning aim D: Understand the factors that are affecting the
Earth and its environment

5. Learning Objectives:
1. Describe the physical and chemical properties of group
1 and 7 elements.
2. Describe trend in the physical and chemical properties
of group 1 and 7 elements.
3. Explain the trend in chemical properties in terms of
electronic structure.
4. Explain the formation of ionic and covalent substances
5. Compare and explain the properties of ionic & covalent
substances, and their applications.
Learning aim A: Investigate chemical reactivity and bonding

6. What we will study today?
• The atomic structure.
• Ionic and covalent bonding
– Properties
– Dot and cross diagram
• Practical – properties of elements.

7. Starter
• Label the atomic diagram
• Complete the fill in gap work sheet
• 10 min

8. Atomic structure
&
Chemical bonding
What things are made of

9. Structure of
magnesium
atoms

10. Closer still…
electron - 12
proton + 12
neutron 0 12
24
12
Mg

11. The Atom: SomeFacts
• Atomsareneutral.Theyhaveno overall charge becausethe numberofprotonsandelectrons
arethe same.
Particle Relative Mass Relative Charge
proton 1 +1
neutron 1 0
electron very small -1
• Atomshavearadiusof0.1 nanometers.

12. Elements
Elements are made of one type of atom only.
Theyarerepresented bybothanameanda symbol.Forexample,
carbon= C andsodium= Na(noticehowthe firstletteris alwaysshownbyacapitalandthe
second is lowercase).

13. Elements
Lookatyourcopyofthe periodictable.Apartfromthe element nameandsymbol,whatelsedo
younotice?
Atomic Number
Mass Number
The atomic number is the number of
protons each atom contains.
The mass number is the total number of
protons and neutrons in the atom.
O
16
8

14. How many protons, electrons and
neutrons does fluorine have?
19
9
F
Atomic weight
Number of protons AND
neutrons
Atomic number
Number of protons
(Number of electrons too)
electron -
Proton +
Neutron 0
9
9
10

15. Atoms andElements Activity
Eachpersonwillbe given a cardwith a question on it. Each
card also has a questionnumber.
Read your questionand recordyour answeron the answer
sheetnextto the appropriatenumber.
Move around the room swapping questioncardswith other
pupils. Each timeyou swap a card, read the questionand
recordyour answer.
There are 30 questions in total.
How many can you complete in
10 minutes?

18. Making of Substances
 There are millions of substances and all have different properties.
But why?
 This is because:
 They are made up of different elements
 How they are held together (the bonding)
 How they are arranged (the structure)

19.  Substances and Molecules are produced by forming different types
of chemical bond.
 In chemical bond, the electrons in the outer shell of the atoms are
rearranged by sharing or transferring.
 When electrons are shared, it is called covalent bonding.
 When electrons are transferred, it is called ionic bonding.
Making of Substances

20. Covalent bonding and substances
 A covalent bond is only formed between two non-metal atoms by
sharing electrons.
 The electrons shared are only from the outer shell – so no electrons
are lost or gained.
 Covalent substance are either separate molecules, e.g. water; or giant
structure like diamond.

21. Types of covalent bonding
Single Covalent Bond
Double Covalent Bond
Quadrupole Covalent
Bond

22. Ionic bonding
 When an atom, or a group of atoms lose or gain electrons to obtain full
outer shells, a new charged particle is formed – called Ions.
 Ions from in reaction between a metal and a non-metal.
In the reaction:
 the metal atoms lose electrons to form positively charged ions
 the non-metal atoms gain electrons to form negatively charged ions
Ionic bonds are strong
electrostatic forces
between oppositely
charged ions

23. Activity
• Identify the statement related to either
covalent or ionic bonding
• 10 min

24. • The bonding between atoms in a covalent molecule is very strong.
• But, there are only very week forces/attraction between the two
molecules in a substance.
• So, simple covalent substances:
 do not conduct electricity even when melted
 have low melting and boiling point – so often gases or liquids
 Not usually soluble in water, but may dissolve in organic solvent.
Properties of simple covalent substances

25. Properties of giant covalent substances
Do you know why diamond is the hardest natural substances? Why
diamond take thousands of year to form?
 Diamond is made up of carbon, which has
four electrons in the outer shell.
 So, it can form four covalent bonds, and
this structural bonding goes on and on
 As a result, it forms a very strong
tetrahedral structure.
 Thereby, it has very high melting and
billing points
Examples of giant covalent substance
include silica, polymer, graphite

26. Properties of Ionic substances
Does an sodium chloride (salt) molecule exist?
NO
 Ions in a solid ionic substances are not
randomly arranged.
 They have a regular, repeating arrangement
called an ionic lattice.
 So, ionic compounds don’t form small
molecules, instead they form crystal with
regular shapes.
 A sodium can surround itself with six chlorides
ions and vice versa – forming a giant ionic
structure.
Properties: high melting and boiling points,
conduct electricity & dissolve in water.

27. Useful Ionic bonds
Since ionic bonds are formed between positively charged and negatively
charged atoms, ionic compounds are strong and with regular structure.
 Most of the earth’s rocks have ionic bonds.
 As a result, the rocks are hard and durable.
 They have high melting and boiling points – solid at RT
 Ionic compounds conduct electricity when melted or in solution.
 They are insulator when solid.

28. Activity
• Complete the table to summarise the properties
of ionic and covalent substances.
• 10 min
Property Covalent substances Ionic substances
Appearance
Solubility
Melting & boiling
points
Electrical
conductivity

29. Properties of ionic & covalent substances
Property Covalent substances Ionic substances
Appearance Solid, liquid or gas at room
temperature
Most are solid or
crystalline at room
temperature
Solubility Many dissolves in organic
solvents, but not in water
Dissolve in water, not in
organic solvent
Melting &
boiling points
Many have low melting and
boiling points
High melting and boiling
points
Electrical
conductivity
Do not conduct electricity Conduct electricity when
molten or dissolved
Discuss in your group to explain why the ionic and covalent substances
have these properties?

30. Activity
• Discuss in your group to explain why the ionic
and covalent substances have the properties.
• Write down your answer

31. Learning Objectives
• Be able to draw and label dot-and-cross
diagram

32. Dot and Cross Diagrams
 Dot and cross diagrams show the arrangement of the outer-shell
electrons in an ionic or covalent compound or element.
 The electrons are shown as dots and crosses
 In a dot and cross diagram:
 Only the outer electrons are shown
 The charge of the ion is spread evenly which is shown by using brackets
 The charge on each ion is written at the top right-hand corner

33. Ionic
compounds
How to draw Dot and Cross Diagrams?
Covalent
compounds
Step 1: Draw the atoms with
their outer shell.
Step 2: Put the atoms together and
check they all have a full outer shell.

34. Example 1: water, H2O
Example 2: oxygen, O2:
O
H H
O O
H
H
O
O O
Step 1: Draw the atoms with
their outer shell.
Step 2: Put the atoms together and
check they all have a full outer shell.
Dot and cross diagrams

35. Activity
Draw dot-and-cross diagrams and write formulae
for the following:
• Covalent: hydrogen, chlorine, carbon dioxide, methane,
water, oxygen.
• Ionic: sodium chloride, magnesium oxide, magnesium
chloride.

37. Practical
Apparatus that I know how to use That I don’t know how to use