Atomic Structure Student Copy

ATOMIC STRUCTURE
1. Relate the number of protons, neutrons and electrons in an atom (including
isotopes) or a monatomic ion, to the atomic number, mass number and charge.
2. State the electron arrangement of atoms and/or ions of the first 20 elements in
the Periodic Table.
3. Relate the charge on monatomic ions to the position of the element on the Periodic
Table.
4. State the electron arrangement of atoms and/or ions of the first 20 elements in
the Periodic Table.
5. Relate the charge on monatomic ions to the position of the element in the Periodic
Table
6. Draw Lewis diagrams of :
• atoms selected from the first 20 elements
• molecules including those with single bonds, e.g. H2O, CH4, H2, Cl2 & PCl3 and
those with multiple bonds

Monday, 3 May 2010

Term Definition GLOSSARY 1 In back of book: match term with defn -> ans’s only

A. atom 1. the absence of electrical charge.
B. element 2. a negatively charged particle that exists outside the nucleus
3. refers to electrons that occupy the outside shell or highest
C. proton
energy level around a nucleus
D. electron 4. a substance that contains only one type of atom
5. the number of particles (protons & neutrons) in the nucleus of
E. neutron
the atom
F. neutral 6. a positively charged particle in the nucleus.
G. atomic number 7. a row of the periodic table
8. the smallest particle that can not be made smaller by simple
H. mass number
chemical means
9. an atom that has the same atomic number as another atom
I. group
but a different mass number
J. period 10. a particle inside the nucleus that has no charge
K. valence 11. the number of protons in the nucleus of an atom
12. a rule that states that most atoms will have a tendency to gain
L. relative
a full outer shell of 8 valence electrons
M. isotope 13. a vertical column of the periodic table
N. octet rule 14. compared to

Monday, 3 May 2010

Term Definition GLOSSARY 1
the smallest particle that can not be made smaller by simple
atom
chemical means
element a substance that contains only one type of atom
proton a positively charged particle in the nucleus.
electron a negatively charged particle that exists outside the nucleus
neutron a particle inside the nucleus that has no charge
neutral the absence of electrical charge.
atomic number the number of protons in the nucleus of an atom
the number of particles (protons & neutrons) in the nucleus of
mass number
the atom
group a vertical column of the periodic table
period a row of the periodic table
refers to electrons that occupy the outside shell or highest
valence
energy level around a nucleus
relative compared to
an atom that has the same atomic number as another atom but
isotope
a different mass number
a rule that states that most atoms will have a tendency to gain
octet rule
a full outer shell of 8 valence electrons
Monday, 3 May 2010

Term Definition GLOSSARY 2 In back of book: match term with defn -> ans’s only

A. a model of a molecule that shows valence electrons as bonding and
1. duet rule
non-bonding pairs
2. valence B. the flow of charge
3. molecule C. a 3D, regular arrangement of particles (ions).
4. crystal D. a non-bonding pair of electrons
E. a bond that comprises three pairs of electrons that are shared
5. lattice
between two nuclei
6. Lewis F. the rule that is obeyed by hydrogen, stating that a hydrogen atom will
structure have a tendency to gain a full outer shell of two electrons.
7. lone pair G. a solid substance that has sharp edges and flat faces
8. single bond H. refers to electrons that occupy the highest energy level of an atom
9. double bond I. a small group of atoms that are covalently bonded to each other
J. a bond that comprises two pairs of electrons that are shared
10. triple bond
between two nuclei
11. anion K. a positively charged ion
12. cation L. a negatively charged ion
13. reactivity M. a measure of the ability of a substance to dissolve in a solvent
N. a bond that comprises one pair of electrons that are shared
14. solubility
between two nuclei
O. a measure of the ability of a substance to participate in a chemical
15. electric current
reaction
Monday, 3 May 2010

Term Definition GLOSSARY 2
the rule that is obeyed by hydrogen stating that a hydrogen atom will
duet rule
have a tendency to gain a full outer shell of two electrons.
valence refers to electrons that occupy the highest energy level of an atom
molecule a small group of atoms that are covalently bonded to each other
crystal a solid substance that has sharp edges and flat faces
lattice a 3D, regular arrangement of particles (ions).
Lewis a model of a molecule that shows valence electrons as bonding and
structure non-bonding pairs
lone pair a non-bonding pair of electrons
a bond that comprises one pair of electrons that are shared
single bond
between two nuclei
a bond that comprises two pairs of electrons that are shared
double bond
between two nuclei
a bond that comprises three pairs of electrons that are shared
triple bond
between two nuclei
anion a negatively charged ion
cation a positively charged ion
a measure of the ability of a substance to participate in a chemical
reactivity
reaction
solubility a measure of the ability of a substance to dissolve in a solvent
electric current the flow of charge
Monday, 3 May 2010

Elements THE BASICS Complete:

Elements are like the letters of the alphabet. There are 26
letters and these can be joined together in different ways to make up to 750 000
different words. Letters cannot be split into anything simpler.

• Elements are substances that contain particles called .
• An element consists of only one type of atom only.
• Atoms cannot be easily into anything .
• There are 90 different elements and these can be .
to make all the other in the world

Atoms
Part of Where Electrical
atom found Charge
Proton
+
+ Neutron
Proton Electron

Word list: substances, atoms,
simpler, split, joined, proton,
electron, empty space, negative,
positive, neutral, neutron, in the
“History of the atom” nucleus, outside the nucleus.
Monday, 3 May 2010

Element names

H Na

He Mg

Li Al

Be Si

B P

C S

N Cl

O Ar

F K

Ne Ca

An easy way to remember the first 20 elements Flashcards
(in exercises)
Harry He Likes Beer By Cupfuls Not Over Flowing
Never Natter Magic Although Science Possesses Some Clues
Arthur Kicks Cats “Element
Bingo” (in starters)
Monday, 3 May 2010

ELECTRON
ARRANGEMENTS

Monday, 3 May 2010

THE PERIODIC TABLE

Hydrogen - not a metal
but here because of its
electron arrangement

1 2 3 4 5 6 7 8

Non-metals

Less reactive
More reactive metals Inert gases
metals

Monday, 3 May 2010

ORGANISATION OF THE PERIODIC TABLE

Atomic number
Atomic numbers are the smaller of the two numbers associated with
each element. Atomic numbers increase by one from left to right of
the table

Rows
The atoms get larger in size from left to right across a row as their
mass increases

Columns
The atoms get larger in size and increase in mass from top to bottom
of a column. Elements in a column have similar properties. Columns
are often called groups.
Groups start at 1 (at the left) and finish with group 8 (at the right of
the table)

Monday, 3 May 2010

MASS NUMBERS & ATOMIC NUMBERS

An element in the periodic table is described like this:
The mass number is 19.
19 The number of protons plus neutrons =19
9 F
Fluorine The atomic number is 9.
There are 9 protons in the nucleus and 9 electrons around it

In this example:
The 19 particles in the nucleus are protons or neutrons I’m lost!
9 of these particles are protons
therefore there are 10 neutrons in the nucleus

Summary

For an atom:
• The atomic number gives the number of protons
• The atomic number is also gives the number of electrons
• The mass number is the number of protons plus neutrons
• neutron number = mass number - atomic number
Monday, 3 May 2010

An exercise done as a class:

4
He This shows how Helium appears in the periodic table
2
Helium

This means: The atomic number is ___.

so there are: 2 protons in the nucleus
and 2 electrons surrounding it

The mass number is ____.

so the number of protons plus neutrons =4
Therefore the number of neutrons must be ___ ( = __ - __)

number of
Symbol of element number of protons number of neutrons
electrons
11 B
5

16 O
8

28 Si 14
35 Cl 20
31 P 15
Monday, 3 May 2010

Individual Exercise TRY THIS!

number of
Symbol of element number of protons number of neutrons
electrons
9 Be
4

21 Ne
10

27 Al 13
39 K 20
15P 16
42 Ca
20

12 C 6
7 Li
3

23 Na
11

24 Mg 12
14 N
7

16S 16
Monday, 3 May 2010

ELECTRON ARRANGEMENTS

Electrons in the electron cloud are not arranged randomly around the nucleus.

• Those close to the nucleus have low energy
• Those far away from the nucleus have high
energy

Electrons are arranged in energy levels

For the 1st 20 elements there are 4 energy levels:

Level 1 can hold a maximum of 2 electrons
Level 2 “ “ “ “ “ 8 electrons

Example 1

20 protons in the nucleus
20
(the atomic number)
Ca => 20 electrons around the
40
nucleus
2.8.8.2

Electron arrangement: “ 2 in the 1st shell, 8 in the 2nd shell, .......
Monday, 3 May 2010

CONFIGURE THIS!

Use your knowledge of electron
arrangement to complete the
table below. The electron 1
arrangements are shown below H
1
the element names Hydrogen
1
4
2 He
Helium
2
7 9 11 12 14 16 19 20
3 Li 4 Be 5 B 6 C 7 N 8 O 9 F 10 Ne
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
2.1 2.2 2.3 2.4
23 24 27 28 31 32 37 40
11 Na 12 Mg 13 Al 14 Si P S Cl Ar
Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon
2.8.1
39 40
K Ca
Potassium Calcium

Monday, 3 May 2010

SHELL DIAGRAMS

Electrons fill up an atoms shell in order, first they fill up the
inner shell (first electron shell) then the next shell and so on

An exercise done as a class:
Process:

40 x 1. Use your periodic table to find the atomic
Ca x x
x x
x

x
number.
x x
Calcium x
x x 2. The atomic number will tell you how
x x
x many electrons there are
x x
x x
x Ca 3. Fill the electrons according to the rule:
Example 2 - Silicon Level 2 “ “ “ “ “ 8 electrons

14
28
Si
28 4. Start filling the levels from level 1.
2.8.4
5. When level 1 is full start filling level 2. When
Si
level 2 is full start filling level 3 and so on.

6. Stop filling the levels when you have used all
the electrons that the atom has.
Monday, 3 May 2010

Individual Exercise A DIFFERENT WAY OF SHOWING IT! Key: p = proton
n = neutron
Example: Fluorine, 9
19F has 9p, 10n, 9e e = electron
e
e For each of the following atoms draw the
electron shell diagram. Show the nucleus as
a solid circle.
n p e e
e n p p
n p n n p A second example
n p p p n
n n
e n p 1. 13
27Al x 2. 11
23Na
x
e x x x

x x x x
e
x x x
e x

3. 14
28Si 4. 15
31P 5. 16
32S

Homework (in science books):
(i) Be (ii) F (iii) Ne (iv) Ar
Monday, 3 May 2010

ATOMS
TO IONS
Monday, 3 May 2010

ATOMS TO IONS
An ion is an atom that has lost or gained electrons
“Ions are more stable than atoms. IONS HAVE AN OUTER SHELL THAT IS FULL...
Using this knowledge it is possible to work out the arrangement of electrons in
ions.”

Sodium atom --> Sodium ion
1 electron
E x x
x x x
lost
x

X
x
x x x
x
x x x

A x x x x
x
x x 1+ charge

M Na Na+

P Chlorine atom --> Chloride ion
1 electron
L
x x
x
x x x x x
x gained
x x x x x

E
x
x x
x x x x
x x x x

S x
x

x
x
x x
x

x
x
x

Cl Cl- 1- charge

Monday, 3 May 2010

IRONING OUT THE IONS
“Metal atoms lose electrons. Non-metal atoms gain electrons.
No more than 3 electrons can be lost or gained”

Copy & complete the following table showing the electron arrangements of the atoms
and their ions:

Metal atom Metal ion Non-metal atom Non-metal ion

C: 2, 4 no ion formed Cl: 2, 8, 7 Cl-: 2, 8, 8

Mg: 2, 8, 2 Mg2+: 2, 8 N: 2, 5 N3-: 2, 8

Li: 2, 1 Li+: 2 Ar: 2, 8, 8 No ion formed

Be O

Ca S

Al F

Na P

Draw small Beryllium Sulphide Aluminium
shell diagrams
for the
following ions
Monday, 3 May 2010

FORMULAE FOR SIMPLE IONS
Background
A chemical formula shows how atoms or ions are joined to make compounds. (A
compound consists of two or more different atoms that are joined chemically).
An ionic compound is formed when positive and negative ions are attracted to each
other. Some ions comprise groups of atoms that have gained or lost electrons. These
groups are the “-ides” or “-ates”.
A table of common ions is shown below:

+1 +2 +3 _,,
-1
H* Mg2* Al3+ c1- gz-
hydrogen magnesium aluminium chloride oxide

Li* Ca2* Fe3* oH- COr'-
lithium calcium iron(III) hydroxide carbonate

Na+ Fe2* No,* Soo'-
sodium iron(II) nitrate sulfate

K+ Cu2* HCO3- PO43-
potasslum copper(II) hydrogen carbonate Phosphate

Zn2*
zinc

Pb2+
lead

Monday, 3 May 2010

GETTING TO KNOW THE “-IDES” AND “-ATES”

“-ates” end in O4 and O3
An exercise done as a class: the rest are “-ides”

+ ion - ion Formula + ion - ron Formula
Znzr N3- ZneNz Ca2* NOs- Ca(NOs)z

Pb2* Br PbBrz Fe3* SO+2- Fe2(S04)3

I Ag* s2- Li* COs2- LizCOs

) Fe3* cl- 6 Ag* PO+3-

3 Na* 02- 7 NH+* SO+2-

K+ t- KI 8 Pbz* COs2-

Cu2* SO+2- CuSOa 9 Al3* oH-
4 Mgz+ COs2- 10 Cu2* s2-

5 Zn2* 02- 11 (+ HCOg-

On the table (above):
1. Circle the “-ates” using a red pen
2. Circle the “-ides” using a blue pen
3. and name them Exercises: “-ide or -ate”
Monday, 3 May 2010

ION FORMATION AND THE PERIODIC TABLE

1 2 Groups of the periodic table 3 4 5 6 7 8

1+ 2+ Charge on ions formed by atoms in each group 3+ 3- 2- 1-

Do not form ions

Monday, 3 May 2010

INTRODUCTION

Monday, 3 May 2010

HISTORY of the atom

See “Nigel’s” ppt on the shared drive

Monday, 3 May 2010

MATTER Nature & State

Monday, 3 May 2010

PROPERTIES OF SOLIDS, LIQUIDS AND GASES BOB: Unscramble

Appearance & Particles Energy Compressibility Melting &
behaviour in a arrangement boiling
container points
A D. Particles are G. The very high J. high M. Moderate
disordered energy of the
and widely particles
SOLID
spaced causes random
& rapid

E. Particles H. The low K. very little N. High
closely energy of the
spaced & particles
arranged in causes them
LIQUID B a lattice. to vibrate
This explains about fixed
the positions
crystalline
appearance
F. Particles are I. The moderate L. virtually O. Low
disordered energy of the none
and closely particles
GAS C
spaced causes them
to move
randomly
Answers: SOLID __ __ __ __ __ LIQUID __ __ __ __ __ GAS __ __ __ __ __
Monday, 3 May 2010

http://
PROPERTIES OF SOLIDS, LIQUIDS AND GASES www.harcourtschool.com/
activity/states_of_matter/

Appearance & Particles Energy Compressibility Melting &
behaviour in a arrangement boiling
container points
Particles are The low energy virtually none High
closely of the particles
spaced and causes them to
arranged in a vibrate about
SOLID fixed positions
lattice. This
explains the
crystalline
appearance
Particles are The moderate very little Moderate
LIQUID and closely particles causes
spaced them to move
randomly
Particles are The very high high Low
GAS and widely particles causes
spaced random & rapid
movement

Monday, 3 May 2010

CHANGES OF STATE

Monday, 3 May 2010

ATOMS, ELEMENTS, COMPOUNDS & MIXTURES

P
U
R
E

Element Element Compound

N
O
T

P
U
R
E
Mixture Mixture
of elements of element with compound

Monday, 3 May 2010

Interactive Complete the mind map

All substances
X
.............. Not pure

...................
Elements ...................

Element
................ with Different
elements compound .................

Questions
1. Explain the difference between Co and CO
__________________________________________________________________
__________________________________________________________________

2. Explain the difference between O2 and 2O
__________________________________________________________________
__________________________________________________________________
Monday, 3 May 2010

Copy ATOMS, ELEMENTS, COMPOUNDS & MIXTURES

• An atom is a particle that cannot be made smaller by simple chemical methods.
• An element is a substance that contains only one type of atom.
• A compound is a substance that contains two or more types of atom chemically
joined together in a constant ration by mass.
• A mixture contains two or more different types of particle.
• A solution is a special mixture where the solid particles are spread evenly
throughout a liquid medium

All substances

Pure Not pure

Mixture
Elements Compounds

Element
Different with Different
elements compound compounds

Ex 3A: 1 to 4 - Answers only
Monday, 3 May 2010

SEPARATING
MIXTURES

Monday, 3 May 2010

SOLUTIONS PRE - TEST (out of 8)

Use the diagram, word list and prior knowledge to complete the cloze
exercise:

1. Salt added to water will form a ______________.

2. Salt is an example of an _________ solid
3. The ions present in salt are ___________ and _____________ .
4. Theses ions arrange themselves into a _____________.

5. Solids with __________ structures have a _____________ appearance. This
means the visible particles have __________ edges and __________ faces.

Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
lattice sodium ionic flat chloride sharp solution crystalline

Monday, 3 May 2010


exercise:
solution



Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
lattice sodium ionic flat chloride sharp crystalline

Monday, 3 May 2010


exercise:
solution
ionic


Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
lattice sodium flat chloride sharp crystalline

Monday, 3 May 2010


exercise:
solution
ionic
sodium


Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
lattice flat chloride sharp crystalline

Monday, 3 May 2010


exercise:
solution
ionic
sodium chloride


Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
lattice flat sharp crystalline

Monday, 3 May 2010


exercise:
solution
ionic
sodium chloride
lattice


Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
flat sharp crystalline

Monday, 3 May 2010


exercise:
solution
ionic
sodium chloride
lattice

Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
flat sharp crystalline

Monday, 3 May 2010


exercise:
solution
ionic
sodium chloride
lattice crystalline

Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
flat sharp

Monday, 3 May 2010


exercise:
solution
ionic
sodium chloride
lattice crystalline
sharp

Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list
flat

Monday, 3 May 2010


exercise:
solution
ionic
sodium chloride
lattice crystalline
sharp flat

Cl- Na+ Cl-

Na+ Cl- Na+

Cl- Na+ Cl-

Word list

Monday, 3 May 2010

SEPARATING MIXTURES
SOLUTIONS VIDEO

Monday, 3 May 2010

Solutions SEPARATING MIXTURES
http://phet.colorado.edu/new/simulations/sims.php?sim=Salts_and_Solubility
An animation showing how substances dissolve:

Solvent

Solute

Solution

Reading with exercises ->
Monday, 3 May 2010

SEPARATING MIXTURES

• Separation techniques based on the differences in the physical properties of the
substances making up the mixture.

Separation Why it can be separated using this
Type of mixture
technique technique
Decanting The particles in the mixture are different
Suspension (Liquid & sizes. Small liquid and solid particles
insoluble solid) pass through whilst larger solid particles
Filtration
do not

The solvent has a lower boiling point and
evaporates away. In the case of two
Solution (containing a Evaporation liquids that are mixed, the liquid with the
solvent & a solute or lower boiling point will evaporate away
two liquids that are
mixed) Based on evaporation but allows the
Distillation solvent or high boiling point liquid to be
kept

Different solvents have different
Solutions that contain solubility in the solvent used so they
Chromatography travel at different speeds alont the
many solutes
chromatography paper

Monday, 3 May 2010

ISOTOPES &
ATOMIC MASS

Monday, 3 May 2010

ATOMIC THEORY
History
1803 - Dalton’s model: “Atoms are indestructible spheres”
1911 - Rutherford: An atom is mainly empty space. It has a central dense,
positively charged nucleus. The nucleus is tiny compared
to the overall size of the atom.
1932 - Chadwick shows that neutrons exist

Atoms
Electron

+ Neutron
+

Proton

Part of Where Relative Electrical
atom found mass Charge
Proton nucleus 1 positive
Neutron nucleus 1 neutral
outside
Electron 0.0005 negative
nucleus

p31 & 32 - ESA -> Ex. 4A: Q.1 to 4 - answers only
Monday, 3 May 2010

ISOTOPES

16 17 18

O O O
8 8 8

Monday, 3 May 2010

ISOTOPES

Atoms with the same atomic number but different mass numbers.
Example
Below are the symbols of the common isotopes of Oxygen.

Notice that the mass numbers are different

16 17 18

O O O
8 8 8

Each isotope has 8 protons
8 neutrons 9 neutrons 10 neutrons
Each different isotope has
different numbers of neutrons

Monday, 3 May 2010

ATOMIC MASS
An isotope has a mass number.
An element that consists of different isotopes will have an atomic mass.

Ex 4B Q.1 to 3 - answers only
Monday, 3 May 2010

ATOMIC MASS

The atomic mass of an element is the weighted average of the mass numbers of all
the isotopes in that element.

Monday, 3 May 2010

ATOMIC MASS


Example
A naturally occurring sample of Copper has 3 atoms of 63
Cu to each one atom of
65
Cu:

63
Cu 63
Cu 63
Cu 65
Cu

Monday, 3 May 2010

ATOMIC MASS


Example
65
Cu:

Atomic mass = 63 + 63 + 63 + 65
63
Cu 63
Cu 63
Cu 65
Cu 4
= 63.5
(or “3 x 63 + 65”)

Monday, 3 May 2010

ATOMIC MASS


Example
65
Cu:

Atomic mass = 63 + 63 + 63 + 65
63
Cu 63
Cu 63
Cu 65
Cu 4
= 63.5
(or “3 x 63 + 65”)

Chlorine is another element which consists of different isotopes. It has an atomic
mass of 35.5

Monday, 3 May 2010

ATOMIC MASS


Example
65
Cu:

Atomic mass = 63 + 63 + 63 + 65
63
Cu 63
Cu 63
Cu 65
Cu 4
= 63.5
(or “3 x 63 + 65”)

Chlorine is another element which consists of different isotopes. It has an atomic
mass of 35.5

Most elements consist mainly of one isotope and therefore their atomic mass is
close to a whole number.

Monday, 3 May 2010

ESA p41 Boron is unshaded because it does not covalently bond with itself??

LEWIS
STRUCTURES
I
Monday, 3 May 2010

ELECTRON CONFIGURATION

• Electrons around the nucleus of the atom have different levels of energy:
• High energy electrons move in regions which are further away from the nucleus
than low energy electrons.

• Greater stability is achieved when the outer energy level is fully occupied by
electrons (usually 8) - this is the octet rule.

Ion formation occurs according to this rule

Example Sodium atom GREATER
Sodium ion
STABILITY

Na Na+

1 electron is lost

Note: Inert gases are stable because the outer level is fully occupied by electrons
Monday, 3 May 2010

ELECTRON PAIRS AND ELECTRON SPINS

“MORE THAN YOU NEED TO KNOW!!”

Electron spins cause magnetic moments.
Think of a magnetic moments as being
like a tiny magnet

Monday, 3 May 2010

ATOM MODELS

Models are used to explain things that we can’t see and/or understand.

Showing only the outer electrons (valence electrons) is a useful model.

Examples - “electron dot diagrams”

Electron configuration is 2.5 but only the 5 valence electrons
N are shown
(the 7 protons and 7 neutrons are not shown in this model)

Electrons are displayed as dots and shown in pairs as they are
thought to occupy the same region in an energy level.
Cl

Monday, 3 May 2010

“CAN YOU SEE THE PATTERN?”

Metal
Key
Borderline but more non - metal

Non - metal

“Which atoms will bond covalently to form molecules?”

Monday, 3 May 2010

COVALENT BONDING

Covalent bonds are formed between non-metal atoms. The bond is
based on the mutual attraction of 2 different positively charged nuclei to the
same pair of negatively charged electrons.

Molecules are formed.

Example: Chlorine, Cl2
Chlorine does not normally exist as individual atoms. Two chlorine atoms pair up to
make a molecule. A pair of electrons is shared between the two atoms:

Each chlorine atom
7 valence
Cl + Cl Cl Cl now has 8 valence
electrons
electrons

A lone pair of electrons A shared pair

“The octet rule is nearly always obeyed except where Hydrogen is involved
in a covalent bond. The outer energy level of hydrogen is fully occupied
when it contains 2 electrons. Hydrogen obeys the duet rule”

Monday, 3 May 2010

LEWIS STRUCTURES

The chlorine molecule drawn (above) is an example of a Lewis structure

Other Lewis structures

Water H2O
O H

H

Hydrogen chloride HCl H Cl

Note
Both the octet and duet rules are both obeyed in the examples (above)
The attraction between atoms is called a bond
A bond can be drawn as a line:

H
H - Cl
O O

Ex 5A Q.1 to 3 - answers only
Monday, 3 May 2010

LEWIS
STRUCTURES
II
DOUBLE & TRIPLE BONDS

Monday, 3 May 2010

DOUBLE BONDS

Sometimes, in order to obey the octet rule, two atoms will need to share
two pairs of electrons.
This TWO shared pair of electrons forms the basis of a double bond.

Examples
Silicon dioxide, SiO2 contains 2 double bonds

O Si O O Si O

TWO pairs are shared The octet rule is
satisfied for each atom
Carbon tetrachloride CCl4 contains only in the molecule
single bonds
Cl Cl

Cl C Cl Cl C Cl

Cl Cl

Monday, 3 May 2010

TRIPLE BONDS

When three pairs of electrons are shared, a triple bond is formed.

Example
Propyne, C3H4

H

H C C C H

H
THREE pairs are shared

Note
• Two atoms joined by a double bond are closer together than two atoms joined by a
single bond. The double bond is shorter and stronger but allows the molecule to be
more reactive because there are more electrons concentrated there.
• The same applies for a triple bond compared to a double bond.

Monday, 3 May 2010

DIFFICULT
LEWIS
STRUCTURES
Monday, 3 May 2010

RESONANCE STRUCTURES

Monday, 3 May 2010

PROCESS FOR DRAWING LEWIS STRUCTURES

1. Add up the total number of electrons
2. Place electron pairs (lone pairs first) around the outer atoms so that the octet/duet
rule is obeyed for these atoms
3. Any lone pairs left over should then be placed around the central atom/s.
4. If you find that the central atom/s does not have an octet then use double or triple
bonding to achieve this

Monday, 3 May 2010



H

H C C C H

H

Monday, 3 May 2010



Step 1: 16 electrons in total H

H C C C H

H

Monday, 3 May 2010



Step 2:
Placing the electron pairs around H C C C H
the outer atoms. (They will all be
bonding pairs in this case).
H

Monday, 3 May 2010



Step 2:
H
There are now 8 remaining pairs

Monday, 3 May 2010



Step 2:
H

Step 3:
Placing the remaining pairs around
the central atoms.

Monday, 3 May 2010



Step 2:
H
There are now 8 remaining pairs This carbon does not
have an octet !!!
Step 3:
the central atoms.

Monday, 3 May 2010



Step 2:
H
There are now 8 remaining pairs This carbon does not
have an octet !!!
Step 3:
Step 4
We will need to use a triple bond on this
the central atoms.
carbon to give it an octet.

Monday, 3 May 2010

“Try again .... and this time GET IT SORTED”

Monday, 3 May 2010


H

H C C C H

H

Monday, 3 May 2010


Step 1: 16 electrons in total

H

H C C C H

H

Monday, 3 May 2010



H
Step 2:
Placing the electron pairs around
the outer atoms. (They will all be H C C C H
H

Monday, 3 May 2010



H
Step 2:
H

Monday, 3 May 2010



H
Step 2:
H

Step 3:
the central atoms.

Monday, 3 May 2010



H
Step 2:
H
There are now 8 remaining pairs THREE pairs are shared

Step 3:
the central atoms.

Monday, 3 May 2010

EXAMPLES

Draw Lewis structures for the following:

(a) PBr3

(b) CH2O

Ex 5A Q.4 & 5 - answers only
Monday, 3 May 2010

EXAMPLES


(a) PBr3

Br

Br P

Br

(b) CH2O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1
Br

Br P

Br

(b) CH2O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br

Br P

Br

(b) CH2O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P

Br

(b) CH2O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O

H

H C O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O

Step 1 H

H C O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O

Step 1 12 electrons H

H C O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O


Step 2 H C O

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O


Step 2 H C O

Step 3

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O


Step 2 H C O

Step 3 But carbon doesn’t have an octet !!

Monday, 3 May 2010

EXAMPLES


(a) PBr3

Step 1 26 electrons
Br
Step 2
Br P
Step 3
Br

(b) CH2O


Step 2 H C O

Step 3 But carbon doesn’t have an octet !!

Step 4
Monday, 3 May 2010

IONIC
SOLIDS
Monday, 3 May 2010

IONIC SOLIDS

Monday, 3 May 2010

IONIC BONDING

Ionic bonds are formed between metal and non-metal ions.
The bond is based on the attraction between positively and
negatively charged ions. Ionic compounds are formed.

Cl- Na+ Cl- “Negative ions are
called anions”

Na+ Cl- Na+

“Positive ions are
Cl- Na+ Cl- called cations”

Note
• Because they are oppositely charged, Sodium and Chloride ions are attracted to
each other.
• This attraction extends in 3 dimensions and results in a huge cubic arrangement
of ions. This arrangement is called a lattice.

Ex 6A Q.1 to 5 - answers only
Monday, 3 May 2010

This is Ann Ion.

Monday, 3 May 2010

This is Ann Ion.
She’s unhappy and
negative.

Monday, 3 May 2010

+ +

This is Ann Ion.
She’s unhappy and
negative.

Monday, 3 May 2010

+ +

This is Ann Ion. This is a cat-ion.
She’s unhappy and
negative.

Monday, 3 May 2010

+ +

This is Ann Ion. This is a cat-ion.
She’s unhappy and He’s a “plussy” cat!
negative.

Monday, 3 May 2010

PERIODIC
TRENDS
Monday, 3 May 2010

THE PERIODIC TABLE

(numbers given to columns)

3 4

(numbers given to rows) Key: show relative atomic size.
Size increases across a row &
decreases down a column.

Note
• There are columns of less reactive metals (transition elements)
between groups 2 and 13
• The dotted line separates metals from non-metals
Monday, 3 May 2010

REACTIVITY OF METALS

The reactivity of a metal is a measure of the metal’s ability to participate in a
chemical reaction.

Metals react when their atoms lose their valence electrons. The easier the electrons
are lost, the more reactive they will be.

Decreasing reactivity

As we move down As we move across a
the group the Li Be period (left to
valence electrons get Lithium Beryllium right),the positive
Increasing reactivity

further from the 2.1 2.2 nucleus increases in
nucleus so they charge so the
become easier to attractive force on
remove.
Na Mg Al the valence electrons
Sodium Magnesium Aluminium increases. Valence
2.8.1 2.8.2 2.8.3 electrons become
Highly more difficult to
reactive
Ca remove.
K
Potassium Calcium
2.8.8.1 2.8.8.2

Monday, 3 May 2010

Atomic Structure Student Copy

Atomic Structure Student Copy

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