Download 11. Patterns in the Periodic Table

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What is the periodic table?
Mendeleev created the first modern periodic table.
What does it show and why is it always in the same order?
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What is an element?
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Where were the elements made?
There are 92 naturally-occurring elements and about 15
artificially-produced elements.
Elements were originally made in
stars. In the early stages of a star’s
life, light elements, such as
hydrogen and helium, are formed.
These fused together to make
heavier elements such as carbon.
Some of the even heavier elements
were produced deep within stars
and were sent out into the Universe
when the stars exploded.
Most of the artificially-produced elements have only been
made in nuclear reactors or particle accelerators.
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What are elements made of?
Each element is made up of one type of atom, which is
different to the atoms in any other element.
Gold is an
element made up
of only gold atoms.
Carbon is an
element made up
of only carbon atoms.
Oxygen is an
element made up
of only oxygen atoms.
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What are atoms made of?
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What is the atomic number?
Every element has a unique atomic number. This is the
number of protons in the nucleus of each atom.
What is the atomic number of
this helium atom?
Helium has 2 protons, so its
atomic number is 2.
Atoms are neutrally charged,
so what links atomic number
and the number of electrons?
electron
proton
neutron
A neutral atom must have equal numbers of protons and
electrons, so the atomic number of an element also gives
the number of electrons.
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What are the properties of elements?
A property is any characteristic feature of a substance.
Can you name any properties
of the element sodium?
Properties of sodium include:
 highly reactive
 solid but melts easily
 feels light (low density).
The chemical properties of an element are
determined by its atomic number.
Are there any patterns in the properties of the elements?
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Elements and atoms – true or false?
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How was the periodic table developed?
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How are the elements arranged?
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The periodic table
Arranging all the elements by their atomic number and their
properties led to the creation of…
…the periodic table
H
He
Li Be
B C N O F Ne
Na Mg
Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? ? ? ? ?
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Missing elements!
In this periodic table the symbols are replaced by atomic
numbers. Some of the numbers are missing – where?
Two more rows of elements fit here.
1
3
4
They are called the lanthanides
and actinides.
11 12
2
5
6
7
8
9
10
13 14 15 16 17 18
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
87 88 89 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
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The elements in the periodic table
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Columns of elements
What are columns of elements called?
1 2
groups
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3 4 5 6 7 0
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Rows of elements
What are rows of elements called?
periods
1
2
3
4
5
6
7
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Complete the sentences – periodic table
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Patterns: metals and non-metals
Where are these different types of elements grouped
together in the periodic table?
 metals
on the left and centre
 non-metals
on the right (except hydrogen)
 semi-metals between metals and non-metals
Semi-metals have some properties similar to metals and
other properties similar to non-metals.
Can you name a semi-metal element?
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Patterns: physical state
Where are these elements of different states grouped
together in the periodic table?
 solids
on the left, in the centre and on the right
 liquids
in the middle and on the right
 gases
on the far right (except hydrogen)
Only two elements are liquids at room temperature.
What are they?
 bromine and mercury
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Metals to non-metals, solids to gases
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Patterns: reactivity of metals
increase in reactivity
What happens to the reactivity of metals along a period?
What happens to the reactivity of metals down a group?
Which is the most reactive metal?
Li Be
Na Mg
Al
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po
Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg
increase in reactivity
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Which metal is more reactive?
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Patterns: reactivity of non-metals
Group 0 elements are the most unreactive of all elements.
Which is the most reactive
non-metal/semi-metal?
increase in reactivity
increase in reactivity
For the remaining nonmetals and semi-metals,
reactivity increases up a
group and along a period
from left to right.
He
B C N O F Ne
Si P S Cl Ar
Ge As Se Br Kr
Sb Te I Xe
At Rn
unreactive
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Which non-metal is more reactive?
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Patterns, atomic number and electrons
The periodic table shows that patterns in the properties of
elements are linked to atomic number.
What links atomic number and the properties of elements?
Electrons!
atomic number = number of protons
number of protons = number of electrons
atomic number = number of electrons
As atomic number increases by one, the number of electrons
also increases by one.
This means that the elements in the periodic table are
also arranged in order of the number of electrons.
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How are electrons arranged?
Electrons are arranged in shells around an atom’s nucleus.
(The shells can also be called energy levels).
Each shell has a maximum number of electrons that it can
hold. Electrons will fill the shells nearest the nucleus first.
1st shell holds
a maximum of
2 electrons
2nd shell holds
a maximum of
8 electrons
3rd shell holds
a maximum of
8 electrons
This electron arrangement is written as 2,8,8.
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Electrons in period 1
Elements in period 1 only have electrons in the first shell.
Why are there only two elements in period 1?
1
1
2
3
4
5
6
7
0
H
He
1
2
The first shell can only hold a maximum of two electrons,
so period 1 only includes the elements hydrogen and helium.
What is special about the outer shell of helium?
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Electrons in period 2
Elements in period 2 all have a complete first shell.
What happens to electrons in the second shell in period 2?
2
1
2
3
4
5
6
7
0
Li
Be
B
C
N
O
F
Ne
2,1
2,2
2,3
2,4
2,5
2,6
2,7
2,8
The second shell is completed one electron at a time going
across the period from left to right.
What is special about the outer shell of neon?
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Electrons in period 3
Elements in period 3 have complete first and second shells.
What happens to electrons in the third shell in period 3?
1
3
2
Na Mg
3
4
5
6
7
0
Al
Si
P
S
Cl
Ar
2,8,4
2,8,5
2,8,6
2,8,7
2,8,8
2,8,1 2,8,2 2,8,3
The third shell is completed one electron at a time going
across the period from left to right.
What is special about the outer shell of argon?
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What are the patterns of electron arrangement?
Consider the electron arrangements of the first 20 elements
in the periodic table.
1
2
3
4
5
6
7
0
2
1
1
2
2,1
2,2
2,3
2,4
2,5
2,6
2,7
3
2,8,1
2,8,2
2,8,3
2,8,4
2,8,5
2,8,6
2,8,7 2,8,8
4
2,8,8,1 2,8,8,2
2,8
What is the pattern of outer shell electrons in a group?
What is the pattern of outer shell electrons across a period?
What is the pattern of full electron shells in a group?
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Electron trends in the periodic table
Trends down a group:
 the number of outer shell electrons is the same;
 the number of complete electron shells increases by one.
The number of a group is the same as the number of
electrons in the outer shell of elements in that group,
except for group 0.
Trends across a period:
 the number of outer shell electrons increases by one;
 the number of complete electron shells stays the same.
The point at which a new period starts is the point at
which electrons begin to fill a new shell.
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Electrons and groups
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Groups and periods
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What’s the electron arrangement?
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Names of groups in the periodic table
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Periodic table and electron structure
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Glossary
 atomic number – The number of protons in an atom.






Sometimes called the proton number.
electron arrangement – A shorthand way of writing the
number of electrons in an atom’s electron shells.
element – A substance made up of only one type of atom.
group – A column in the periodic table containing elements
with the same number of outer shell electrons and similar
chemical properties.
period – A row in the periodic table containing elements
with the same number of full electron shells.
periodic table – The table that lists all the elements in
order of increasing atomic number, arranged into groups and
periods.
property – Any characteristic of an element.
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Anagrams
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Multiple-choice quiz
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