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Transcript of Reactions P
BONDING
K Warne
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Periodic Table Test
Give the names of
the following
elements:
1. Na
2. S
3. N
4. C
5. Ca
6. Cu
7. F
8. Ne
9. Pt
10. Mg
Give the SYMBOL
of the following
elements:
1. Iron
2. Chrome
3. Lead
4. Mercury
5. Gold
6. Platinum
7. Phosphorus
8. Uranium
9. Nickel
10. Silicon
Bonding
O
H2O
O
H2O
O O
Two hydrogen molecules and one oxygen molecule react to form two water
molecules.
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H H
Reactions
H2 + Cl2 2HCl
3H2 + N2 2 NH3
H H Cl Cl Cl H Cl H
H H N N N
H H
N
H H H
H
H H
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Covalent bond
A shared PAIR of electrons. Electrons from one atom are attracted strongly by the
nucleus of another atom.
Formed between non metals. (Attract electrons strongly!)
Pure covalent bonds have EQUAL SHARING of the
electrons.
In diatomic Molecules; H2, O2, F2, Cl2, Br2, I2, N2,
H H
In covalent substances the electrons are strongly held in the bonds
and so the substance will NOT conduct electricity.
H H • x
Couper structure
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Covalent Molecules – Bohr Diagrams
H2, O2, F2, Cl2, Br2, N2, H2O, NH3, CH4
O O
p=8
n=8
p=8
n=8
O=O O2
Two shared
electron pairs
Two shared
electron pairs
form a DOUBLE
covalent bond!
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F F
Fluorine F2
p=9
n=10
p=9
n=10
F-F
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Diatomic Molecules
O2 indicates that two oxygen atoms are BONDED
together into an oxygen molecule.
2O just indicates that you have two oxygen atoms.
O2 2O What is the difference?
O O O O
O2=Bonded
oxygen molecule
NOT bonded = 2O
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Covalent Molecules CH4
H
H
C
C
H
methane
C H
H
H
H
Since carbon has 4
valence electrons 4
hydrogens are needed
4 shared pairs = 4
covalent bonds
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x
x
Covalent Molecules N2
N
N
N N x x x
3 shared pairs is a
triple bond
One lone or
unbonded pair
each
NN
A triple covalent bond
is very strong so
nitrogen is VERY
UNREACTIVE!
~70 % of the
atmosphere is nitrogen
– it does not react with
almost anything!
Nitrogen is used in
crisp packets to keep
the crisps fresh
because it does NOT
react with them.
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Ionic Bonding
Formed when there is a ………….
of …………………...
Formed between ………….. and ………………….
Metals …………………….. and
become ……………………... ions - CATIONS.
Non metals …………………... and become …………………………. ions - ANIONS.
…………………………… between oppositely charged ions bonds the ions together.
Na.
..
:Cl: -
.. Na
+
.
:Cl:
..
..
Na. + : Cl: --> [Na]+ [Cl]
-
.
ELECTROSTATIC
ATTRACTION
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F-
Fluoride F- Bohr Diagram
p=9
n=10
-1
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P=8
N=8
2-
+ 2e-
Oxygen
(Atom)
Oxide
(ion)
P=8
N=8
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Ionic Bonding – Bohr Diagrams
The final compound is ALWAYS NEUTRAL
The total charges of the cations and anions must balance
out.
p=17 n=18
Cl
p=17 n=18
Cl- formula
-1
p=11 n=12
Na
p=11 n=12
Na+
+1
Chlorine
atom
Chloride ion (Bohr diagram)
Sodium atom Sodium ion Na
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Li
Br2
P=
35
n=
45
p=
35
n=
45
Br -
p=
35
n=
45
2Li + Br2
2LiBr
Br -
p=
35
n=
45
- -
+ +
Li+ Li
+
Li
Formation of Lithium Bromide
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MUST BE LEARNT BY HEART! ONE TWO THREE
Hydrogen H+ Beryllium Be
2+ Aluminium Al
3+
Lithium Li+ Magnesium Mg
2+ Iron(III) Fe
3+
Sodium Na+ Calcium Ca
2+
Potassium K+ Barium Ba
2+
Silver Ag+ Lead Pb
2+
Copper(I) Cu+ Zinc Zn
2+
Ammonium NH4+ Iron(II) Fe
2+
Oxonium H3O+ Copper(II) Cu
2+
VALENCY TABLE 1
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Bonding - Metallic Bonding
- Exists between _________________.
- Metal electrons are _____________ - therefore they become ______________________ (move from one atom to another).
- This leaves _______________ - which become surrounded by a ‘sea’ of ______________________ electrons.
- A force of _______________________ exists between the delocalized ___________________ and the positive ___________- which forms the ___________________ bond.
All the _____________ of
metals can be explained
in terms of this bonding.
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Bonding Summary
Covalent Non metals
Shared
electrons
Molecules
Ionic
• Metals + non metals
• +/- Ions - Lattice
• electrostatic attraction
Metallic
• Metals
• “delocalised” electrons
H x H •
Cl- Na+
Properties • Non - conducting
• (Electrons held in
bond.)
• V Low or V High
melting points
• Insoluble (H2O)
Properties • High Melting points
• Soluble (H2O)
• Conduct electricity when
ions free to move(liquid
or solution).
Properties • Good Conductors
• Malleable
• Ductile
• Luster (shiny).
H-H
Eg Hydrogen (H2)
Bonding Element Number of Bonds(Valency)
Lithium 1
Magnesium 2
Silicon 4
Phosphorus 3
Chlorine 1
Aluminum 3
Arsenic 3
Helium 0
Nitrogen 3
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Valency - No of Bonds
Element
Symbol Group No Period
Valence
electrons
Valency
(Bonds)
Na 1 3 1 1
N
Cl
6 2
1 2
7 2
B 3 2 3 5
Be 2 2
Al 3 3
Si 4 4
H
Hydrogen is an exception - it often reacts as a metal!
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Bonding Element 1 &
Valency
Element 2 &
Valency
Element 1 -
bonds
Element 2 -
bonds
Compound Formulae
Na +1 Cl -1 Na — Cl— Na —Cl NaCl
H +1 O -2 H— O — H
O
H
H2O
Na +1 S -2
Ca O
H C
Li O
Si O
C O
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Hi -
This is a SAMPLE presentation only.
My FULL presentations, which contain loads more slides (with all the gaps filled in) as well as
other resources, are freely available on my resource sharing website:
www.sciencecafe.org.za
(paste into your browser if link above does not work)
Have a look and enjoy!
Keith Warne