Transcript The Periodic Table

KS4 Chemistry
The Periodic Table
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Atomic number, charge and electrons
Atoms contain equal numbers of protons and electrons.
This means that atoms are neutral.
What is the charge of a fluorine atom?
9 protons
9 electrons
10 neutrons
= +9
= -9
= 0
Total charge =
0
What links atomic number and the number of electrons?
atomic number = the number of electrons in an atom
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Mendeleev and the periodic table
Mendeleev created the first modern periodic table by
grouping together elements with similar properties.
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Atomic number and patterns of behaviour
If the elements are arranged in order of increasing atomic
number, patterns in their properties can be seen.
reactive gases
reactive metals
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K
unreactive gases
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Positions of similar elements
Compare the positions of similar elements:
reactive gases
reactive metals
H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K
unreactive gases
How many elements from one reactive gas to the next?
8
How many elements from one reactive metal to the next?
8
How many elements from one unreactive gas to the next? 8
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Arranging elements
Divide the elements at set intervals into separate rows:
cut here
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H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K
Arrange these rows so elements with matching properties
are together:
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K
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Arranging elements into columns
When elements are arranged according to their properties
what patterns do you see?
hydrogen
is a special
case
H
He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K
reactive metals
reactive gases
unreactive gases
Similar elements go into the same columns.
Hydrogen is an exception – it is best positioned above the
reactive metals.
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The periodic table
Arranging all the elements by their atomic number and their
properties led to the creation of…
H
…the periodic table
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
11 12
2
They are called the lanthanides
5 6 7 8 9 10
and actinides and are only
shown on some periodic tables. 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 38 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
H
groups
3 4 5 6 7 0
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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Rows of elements
What are rows of elements called?
periods
1
H
2
Li Be
B C N O F Ne
3 Na Mg
Al Si P S Cl Ar
4
He
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
7 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? ? ? ? ?
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Multiple-choice quiz
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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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Patterns of electron arrangements
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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Groups and periods
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What’s the electron arrangement?
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