C4: The Periodic Table

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C4 The Periodic Table
OCR Gateway Additional Science
W Richards
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Fundamental Concepts
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Elements
If a solid, liquid or gas is made up of only one
type of atom we say it is an element. For
example, consider a tripod made up of iron
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Compounds
Compounds are formed when two or more elements
are chemically combined. Some examples
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Chemical formulae
The chemical formulae of a molecule or compound
is simply a way of showing the ratio of atoms in
it. For example
sodium chloride (NaCl)
potassium iodide (KI)
potassium nitrate (KNO3)
K
N
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Some simple compounds
Carbon dioxide, CO2
Water, H2O
Ethyne, C2H2
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Chemical formulae

• Try drawing these
• Water H2O
• Carbon dioxide CO2
• Calcium sulphate CaSO4
• Magnesium hydroxide Mg(OH)2

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Naming compounds
Rule 1 If two identical elements combine then
the name doesnt change
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Naming compounds
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Naming compounds

1. Potassium hydrogen oxygen
2. Lithium hydrogen oxygen
3. Calcium hydrogen oxygen
4. Mg(OH)2

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Naming compounds
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Balancing equations
Consider the following reaction


This equation doesnt balance there are 2
hydrogen atoms on the left hand side (the
reactants and 3 on the right hand side (the
products)
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Balancing equations
We need to balance the equation


Now the equation is balanced, and we can write it
as
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Some examples
2 2 2 3
2 2 2 2 3
2 2 2 2 2 4
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Simple formulae to learn
Covalent formulae
Ionic formulae
H2O CO2 NH3 H2 O2 N2 SO2
Water Carbon dioxide Ammonia Hydrogen Oxygen Nitro
gen Sulphur dioxide
NaCl CaCl2 MgO HCl H2SO4 HNO3 NaOH Ca(OH)2 CaCO3 A
l2O3 Fe2O3
Sodium chloride Calcium chloride Magnesium
oxide Hydrochloric acid Sulphuric acid Nitric
acid Sodium hydroxide Calcium hydroxide Calcium
carbonate Aluminium oxide Iron oxide
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C4a Atomic Structure
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Atomic Structure Revision
19/06/2014
I did some experiments in 1808 that showed that
everything in the world was made up of particles
called atoms which are only 10-10 m big and
have a mass of 10-23 g
Dalton
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Mass and atomic number
19/06/2014
Particle Relative Mass Relative Charge
Proton 1 1
Neutron 1 0
Electron Very small (0) -1
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Mass and atomic number
19/06/2014
How many protons, neutrons and electrons?
1
11
16
H
B
O
1
5
8
23
35
238
Na
Cl
U
11
17
92
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Isotopes
19/06/2014
An isotope is an atom with a different number of
neutrons
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Electron structure
19/06/2014
Consider an atom of Potassium
Potassium has 19 electrons. These electrons
occupy specific energy levels shells
The inner shell has __ electrons The next shell
has __ electrons The next shell has __
electrons The next shell has the remaining __
electron
Electron structure 2,8,8,1
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Electron structure
19/06/2014
Draw the electronic structure of the following
atoms
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24
14
Ca
Mg
N
7
20
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Electron structure 2,8,8,2
Electron structure 2,8,2
Electron structure 2,5
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The Development of Atomic Structure Theory
Task Find out how the following people have
contributed to our understanding of atomic
theory, including what they discovered and how
their ideas were proved
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C4b Ionic Bonding
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Bonding introduced
19/06/2014
Hi. My names Johnny Chlorine. Im in Group 7,
so I have 7 electrons in my outer shell







Id quite like to have a full outer shell. To do
this I need to GAIN an electron. Who can help me?
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Bonding
19/06/2014
Here comes my friend, Sophie Sodium
Hey Johnny. Im in Group 1 so I have one
electron in my outer shell. Im quite happy to
get rid of it. Do you want it?
Okay
Now weve both got full outer shells and weve
both gained a charge. Were both called IONS and
weve formed an IONIC bond.
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Ions
An ion is formed when an atom gains or loses
electrons and becomes charged
If we take away the electron were left with
just a positive charge
This is called an ion (in this case, a positive
hydrogen ion)
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Ionic bonding
This is where a metal bonds with a non-metal
(usually). Instead of sharing the electrons one
of the atoms _____ one or more electrons to the
other. For example, consider sodium and chlorine
Sodium has 1 electron on its outer shell and
chlorine has 7, so if sodium gives its electron
to chlorine they both have a ___ outer shell and
are ______.
Group 1 _______ will always form ions with a
charge of 1 when they react with group 7
_______. The group 7 element will always form a
negative ion with charge -1.
Words full, transfers, positively, negatively,
metals, halogens, stable
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Some examples of ionic bonds
Magnesium chloride

MgCl2
Calcium oxide
CaO
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Giant Ionic Structures
When many positive and negative ions are joined
they form a giant ionic lattice where each ion
is held to the other by strong electrostatic
forces of attraction. This is an ionic bond

• Sodium chloride and magnesium oxide are two
  examples of chemicals bonded in this way. If
  these ions are strongly held together what affect
  would this have on the substances
• Melting point?
• Boiling point?
• State (solid, liquid or gas) at room temperature?

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Dissolving Ionic Structures
When an ionic structure like sodium chloride is
dissolved it enables the water to conduct
electricity as charge is carried by the ions
Cl-
Na
Cl-
Na
Cl-
Na
Cl-
Na
Cl-
Na
Cl-
Na
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C4c The Periodic Table and Covalent Bonding
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Bonding revision
Hi. My names Johnny Chlorine. Im in Group 7,
so I have 7 electrons in my outer shell







Id quite like to have a full outer shell. To do
this I need to GAIN an electron. Who can help me?
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Covalent Bonding
19/06/2014
Here comes one of my friends, Harry Hydrogen
Hey Johnny. Ive only got one electron but its
really close to my nucleus so I dont want to
lose it. Fancy sharing?
Now were both really stable. Weve formed a
covalent bond, a bond that often forms between
non-metals.
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Covalent bonding
Consider an atom of hydrogen
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Dot and Cross Diagrams
Water, H2O
O
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Dot and Cross Diagrams
Oxygen, O2
O
O
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Dot and cross diagrams
Water, H2O
Step 1 Draw the atoms with their outer shell
Step 2 Put the atoms together and check they all
have a full outer shell
Oxygen, O2
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Dot and cross diagrams
Nitrogen, N2
Methane CH4
Ammonia NH3
Carbon dioxide, CO2
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Properties of simple molecules
Recall our model of a simple covalent compound
like hydrogen, H2
Hydrogen has a very low melting point and a very
low boiling point. Why?
Also, the molecules do not carry a charge so
covalent compounds usually do not conduct
electricity. Carbon dioxide and water are two
more examples of covalent molecules that behave
in a similar manner.
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Periodic Table Introduction
19/06/2014
How would you arrange these elements into groups?
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Periodic table







Horizontal rows are called PERIODS
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The Periodic Table
Fact 1 Elements in the same group have the same
number of electrons in the outer shell (this
corresponds to their group number)
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg

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The Periodic Table
Fact 2 As you move down through the periods an
extra electron shell is added
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg

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The Periodic Table
Fact 3 Most of the elements are metals
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg

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The Periodic Table
Fact 4 (Most important) All of the elements in
the same group have similar PROPERTIES. This is
how I thought of the periodic table in the first
place. This is called PERIODICITY.
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg

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Development of the Periodic Table
Li Be B C N O F Na Mg Al
Li Be B C N O F Na Mg Al
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C4d The Group 1 Elements
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Group 1 The alkali metals
19/06/2014
Li
Na
K
Rb
Cs
Fr







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Group 1 The alkali metals
Some facts







1) These metals all have ___ electron in their
outer shell.
2) Density increases as you go down the group,
while melting point ________
2) Reactivity increases as you go _______ the
group. This is because the electrons are further
away from the _______ every time a _____ is
added, so they are given up more easily.
3) They all react with water to form an alkali
(hence their name) and __________, e.g
Words down, one, shell, hydrogen, nucleus,
decreases
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Properties of the Alkali Metals
Element Melting Point (OC) Boiling Point (OC) Density (g/cm3)
Lithium 180 1340 0.53
Sodium 98 883 0.97
Potassium 64 760 0.86
Rubidium 39 688 1.53
Caesium ?? ?? ??
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Trends in Group 1
Consider a sodium atom
Sodium ion
Now consider a potassium atom
Potassium ion
Potassium loses its electron more easily because
its further away potassium is MORE REACTIVE
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Flame tests for group 1
Compounds containing lithium, sodium, potassium,
calcium and barium ions can be recognised by
burning the compound and observing the colours
produced
Lithium Red
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C4e The Group 7 Elements
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Group 7 The halogens
F
Cl
Br
I
At








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Group 7 The Halogens
Some facts







1) Reactivity DECREASES as you go down the group
(This is because the electrons are further away
from the nucleus and so any extra electrons
arent attracted as much).
2) They exist as diatomic molecules (so that
they both have a full outer shell)
3) Because of this fluorine and chlorine are
liquid at room temperature and bromine is a gas
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The Halogens - Chlorine
Chlorine is commonly used to sterilise water and
to make plastics and pesticides.
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The Halogens - Bromine
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The Halogens - Iodine
Iodine is a solid at room temperature but with
gentle heating it will melt. The atoms will
remain in pairs. In solid form iodine is grey
like metal and is used to sterilise wounds.
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Properties
Element Melting Point (OC) Boiling Point (OC) Density (g/cm3)
Flourine -220 -188 0.0016
Chlorine -101 -34 0.003
Bromine -7 59 3.12
Iodine 114 184 4.95
Astatine ?? ?? ??
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Trends in Group 7
Consider a fluorine atom
Fluoride ion
Now consider a chlorine atom
Chloride ion
Chlorine doesnt gain an electron as easily as
fluorine so it is LESS REACTIVE
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The halogens some reactions
1) Halogen metal

2) Halogen non-metal

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Displacement reactions
To put it simply, a MORE reactive halogen will
displace a LESS reactive halogen from a solution
of its salt.
Potassium chloride KCl(aq) Potassium bromide KBr(aq) Potassium iodide KI (aq)
Chlorine Cl2
Bromine Br2
Iodine I2
F
Cl
Br
I
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C4f Transition Metals
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The Transition Metals







Some facts
1) They are all ______ and solid (except
_________)
2) They are ____ reactive than the alkali metals
3) They can form __________ compounds, usually
_______

1. They can be used as a ______ (a chemical that
   speeds up a reaction)
2. Copper and iron are two common examples

Words hard, coloured, mercury, less, catalyst,
insoluble
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Thermal decomposition of carbonates
19/06/2014
Transition metal carbonates undergo thermal
decomposition when heated. For example, consider
copper carbonate
Now write word and symbol equations for the
thermal decomposition of iron, manganese and zinc
carbonate.
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Testing for metal ions
Some metal ions form precipitates, i.e. an
insoluble solid that is formed when sodium
hydroxide is added to them. Consider calcium
chloride
Metal ion Precipitate formed Colour
Calcium Ca2 Calcium hydroxide Ca2(aq) OH-(aq) Ca(OH)2 (s) White
Aluminium Al3
Magnesium Mg2
Copper(II) Cu2
Iron(II) Fe2
Iron(III) Fe3
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C4h Metal structure and properties
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The Periodic Table
19/06/2014
Recall something we said earlier some of the
elements are metals
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg

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Properties of metals
19/06/2014
Metals have very high melting points (which means
that they are usually _____) whereas non-metals
will melt at lower ___________ All metals conduct
heat and __________ very well, whereas non-metals
dont (usually) Metals are strong and ______ but
bendable. Non-metals are usually _____ or they
will snap. Metals will _____ when freshly cut or
scratched, whereas non-metals are usually
dull. Metals have higher _______ than non-metals
(i.e. they weigh more) Metals can be used to make
______ (a mixture of different metals)
Words - alloys, electricity, solids, weak,
densities, temperatures, tough, shine
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Copper, Aluminium and Titanium
19/06/2014
Metal Uses and why Extraction method Problems
Copper Electrical wires good conductor Electrolysis Limited supply
Aluminium and titanium Planes light and corrrosion resistant Complicated and expensive Expensive and difficult to extract
Supplies of any raw material are limited so what
are the options?
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Using Iron
19/06/2014
Iron produced by the blast furnace (cast iron)
contains about 96 iron and 4 impurities. These
impurities make it very brittle and easy to break.
Ironbridge, Shropshire made out of cast iron
and safe for horses and carts but not modern
vehicles.
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A closer look at metals
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Understanding Resistance
Metals have delocalised electrons that enable
them to conduct electricity and heat very well
The ability of these electrons to move around
means that metals can conduct electricity.
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Superconductivity
In 1911 I discovered superconductivity. This is
when a metal can conduct electricity with zero
resistance. I won the Nobel Prize for this
discovery in 1913.
Superconductors can have many benefits, including
loss-free power transmission, super-fast
electronic circuits and powerful electromagnets
like in this train. But what are the drawbacks?
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C4h Purifying and Testing Water
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Water

• Amazing facts about water
• 95 of your body mass is water (94 in women due
  to a higher body fat content)
• Dinosaurs would have drunk the same water you do
• Water dissolves more substances than any other
  liquid most ionic substances are soluble and
  most covalent substances are insoluble
• Around 75 of the worlds surface is made of
  water
• To feel thirsty you need to lose around 1 of
  your body water
• 5,000 children die every day due to not having
  clean drinking water
• An average person in the West uses 200-300 litres
  of water every day

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Water resources
There are many different water resources in the
United Kingdom
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Pollutants in water
Many different pollutants can find their way into
our water
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Water
Water often contains various microbes, dissolved
minerals and pollutants. For water to be used as
drinking water it has to be treated
The Water Treatment Process
Pure water can also be produced by distillation
of sea water but this is expensive.
1) Sedimentation
2) Filtration
3) Chlorination
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Testing for chloride, bromide and iodide ions
For each test state 1) The colour of the
precipitate 2) What compound it is 3)
Write an equation for it
Test 1 Chloride ions Add a few drops of dilute
nitric acid to the chloride ion solution followed
by a few drops of silver nitrate.
Precipitate formed silver chloride (white)
Test 2 Bromide and iodide ions Add a few drops
of dilute nitric acid followed by a few drops of
silver nitrate solution. A pale yellow
precipitate should be formed for bromide ions and
a darker yellow precipitate for iodide ions.