Higher chemistry

1
Higher chemistry

• Unit 1
• Section 1 Elements and Bonding

2
1.1 Metallic elements

• See intro on scholar 5.2 chemical bonding with
  animation on structure of sodium atom
• Follow with 5.2.1 metallic bonds animation
• http//courses.scholar.hw.ac.uk/vle/scholar/sessio
  n.controller?actionviewContentcontentGUID4981b4
  82-45ec-4ad4-dd4c-47960338e6a3

3
1. Metallic lattice

• Metallic bonding is the electrostatic force of
  attraction between positively charged ions and
  delocalised outer electrons.
• A metallic structure consists of a giant lattice
  of positively charged ions and delocalised outer
  electrons.

4
2. Physical properties

• In a metallic lattice the delocalised electrons
  can move freely so it is a good conductor of
  electricity
• Metals are malleable (able to be rolled into
  sheets) and ductile (able to be stretched out)
  because the metallic bond can move around as the
  atom is moved.

5
3 Melting and Boiling points

• Melting and boiling involve breaking bonds or
  forces of attraction. The higher the melting and
  boiling points are, the greater the number and/or
  strength of the bonds.
• See scholar melting point animation on 7.2 and
  look at trends down group 1 and across a period
  for metals

6
Melting / boiling point trend down the group

• The melting point decreases down the group.
• As the metal increases in size the delocalised
  outer electrons are further from the positively
  charged centres so the force of attraction
  decreases.
• Breaking the weaker forces requires less energy
  and therefore a lower temperature is enough to
  melt the metal.

7
Melting / boiling point trend across the metallic
elements

• The melting point increases across the period.
• As the metal increases in size there are more
  delocalised outer electrons so the force of
  attraction increases.
• Breaking the stronger forces requires more energy
  and therefore a higher temperature is needed to
  melt the metal.

8
1.2 Monatomic Elements

• See scholar melting point animation on 7.2 and
  look at group 0.
• Van der Waals' forces of attraction are the only
  type of force holding the particles of Group 0
  elements together as a solid.
• The larger the atom the stronger the van der
  Waals' forces.

9
2.Van der Waals Forces

• See scholar 6.2 Van der Vaals forces and play the
  induced dipoles animation
• Draw the examples of the induced dipole into
  notes.
• A temporary dipole is a momentary separation of
  charge due to electrons being unevenly
  distributed.
• The temporary dipole causes an induced dipole to
  be formed in neighbouring particle
• Van der Waals force is an example of an
  intermolecular attraction.

10
3 Noble gas series

• Use data booklet to find boiling points of noble
  gases. Sketch a graph of boiling point for the
  noble gases.
• As atomic size increases so does the wobble and
  so increases the Van der Waals force.
• The larger the force the more energy needed to
  separate so higher boiling point.

11
1.3 Molecular elements

• Atoms in a covalent bond are held together by
  electrostatic forces of attraction between
  positively charged nuclei and negatively charged
  shared electrons.
• A covalent molecular structure consists of
  discrete molecules held together by
  intermolecular forces.

12
1 Diatomic elements

• Draw diagram of two fluorine molecules to show
  both covalent bond within molecule and the Van
  der Waals between them.
• Use data booklet to find melting points of
  halogens (group 7). Sketch a graph of melting
  point for the halogens
• What type of bonding / force is broken on melting
  the halogens?

13
2 Larger covalent molecules

• Check if animation on scholar 5.2.2.2 is working
• Use models of chlorine, phosphorus and sulphur to
  illustrate m.p.
• White phosphorus (Youtube link)
• The larger the molecule the larger the Van der
  Waals so more energy needed to separate the
  molecules so higher temperature needed to
  separate the molecules.

14
3. Molecular carbon

• Fullerenes exist as molecules containing 60 or
  more carbon atoms. C60
• Cut out sheet
• Covalent molecules have low melting and boiling
  points as only weak forces between the molecules
  are broken on melting

Recently carbon nanotubes have been developed
BBC weblink
15
1.4 covalent network elements

• Check if animation on scholar 5.2.2.2 is working
• Show diamond model or 7.1 on scholar
• Cut out sheet
• Diamond has strong bonds linked in a giant
  covalent network.
• The structure is very hard and rigid, since
  breaking a few bonds means breaking up the whole
  network.

16
1.4.2 covalent network elements
There are only three elements that have covalent
network structures. Boron, carbon and silicon.
They are all solids due to a covalent network
structure.
C
They have high melting points as it is strong
covalent bonding that has to be broken when
melting
17
1.4.3 graphite

• Check if animation on scholar 5.2.2.2 is working
• Model of graphite structure
• Cut out sheet
• Graphite will conduct electricity as it has
  electrons that can move freely along the layers.
• Graphite can be used as a lubricant as it has
  layers that can slide.

18
1.5 atomic size

• Draw diagram to show the difference between
  covalent radius and the van der waals radius.
• Down a group the covalent radius increases due
  to more energy levels
• Across a row the covalent radius decreases
  because the nucleus has a stronger attraction for
  the outer electrons

19
Periodic Trends- Covalent Radius.
Trend across the second Period (Lithium to
Fluorine).
Note- there are no values given for the noble
gases in group 8 as they do not form covalent
bonds.
20
3. Atomic size and density

• Use scholar 4.3.1 to help with this
• Density is the mass per volume
• The greater the mass the greater the density and
  the larger the size the less its density.
• Size however only affects the density of liquids
  and solids.

21
3. Atomic size and density

• For metals
• Down a group the density increases because the
  atomic mass increases more than the increase in
  size
• Across a row the density increases because atomic
  mass is increasing and the atomic size is
  decreasing.

22
1.6 Ionisation Energies

• The first ionisation energy is the energy needed
  to remove one electron from every atom in a mole
  of free atoms
• It is measured in kilojoules per mole
• kJmol -1
• Write out symbol equations and values for first
  ionisation of sodium and for chlorine

23
2. Trends across row and down group

• See graph on scholar 4.4 and figures 4.13 and
  4.14
• Explain fully the trend down a group
• Explain fully the trend across a row

24
Periodic Trends- First ionisation energy.
The first ionisation energy for lithium is the
energy that has to be supplied for remove one
mole of electrons from one mole of lithium atoms
in the gas state ie it is DH for Li(g) ?
Li(g) e-
2500
2250
First ionisation energy (kJ mol-1)
2000
Group 1
1750
1500
1250
1000
750
500
250
H He Li Be B C N O F
Ne Na Mg Al Si P S Cl Ar K
Ca
Element
25
2. Trends across row and down group

• See graph on scholar 4.4 and figures 4.13 and
  4.14
• Explain fully the trend down a group
• Explain fully the trend across a row

26
Periodic Trends- First ionisation energy.
The first ionisation energy for lithium is the
energy that has to be supplied for remove one
mole of electrons from one mole of lithium atoms
in the gas state ie it is DH for Li(g) ?
Li(g) e-
2500
2250
First ionisation energy (kJ mol-1)
2000
Row 2
1750
1500
1250
1000
750
500
250
H He Li Be B C N O F
Ne Na Mg Al Si P S Cl Ar K
Ca
Element
27
3. Second ionisation energy

• See scholar 4.4
• Write out definition of second ionisation energy.
• Write out symbol equation to illustrate second
  ionisation energy of carbon with the energy value

28
1.7 Periodic Pattern

• See scholar 4.2 history of periodic table
• Work through the animations on Newlands octaves
  and Mendeleevs periodic table

weblink
29

• The Periodic Table is based on the work of
  Mendeleev who arranged the known elements in
  order of increasing atomic masses in conjunction
  with similar chemical properties, leaving gaps
  for elements yet to be discovered.
• The modern Periodic Table lists the elements in
  order of atomic number and takes into account the
  electron arrangements of the atoms of the
  elements.

30
Bonding in the first 20 elements
H
He
Be
C
N
Li
F
Ne
B
O
Na
Si
P
Al
Cl
Ar
S
Mg
K
Ca
31
H
He
Ne
Be
C
N
Li
F
B
O
Ar
Na
Al
Si
P
Cl
S
S
Mg
K
Ca