Can you recall

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Can you recall

• What is Matter?
• Matter is anything that has mass and takes up
  space.

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What is matter made of?
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Democritus
if one were to break up matter into smaller and
smaller piece, there would come a point when it
could no longer be divided further. He called
this smallest indivisible bit of matter atom
(from the Greek word atomos which means
indivisible).
Greek Philosopher (460 B.C. 370 B.C.)
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Particles that make up of matter

• Using a Scanning Tunneling Microscope (STM),
  scientists are now able to observes the particles
  that make up matter.

Gold atoms
Scanning Tunneling Microscope
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Particles that make up of matter
Iron on Copper
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What is an atom?
An atom is the smallest unit of an element,
having the properties of that element.
Atom!
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Given that

• an atom is the smallest unit of an element,
  having the properties of that element
• Question for thought
• Is a copper atom identical to a zinc atom?

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Lets learn more about the ATOM
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Model of an Atom
Are atoms like solid balls?
With nothing else inside?
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The Changing Model of the Atom

• The history of atom
• Dalton model (Billiard Ball Model)
• Thomson model (Plum Pudding Model)
• Lewis model (Cubical Atom Model)
• Nagaoka model (Saturnian Model)
• Rutherford model (Planetary Model)
• Bohr model (RutherfordBohr Model)
• BohrSommerfeld model (Refined Bohr Model)
• Gryzinski model (Free-fall Model)
• Schrodinger model (Electron Cloud Model)

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The Ever Changing Model
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Presenting to you
The Bohr Model
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Particles smaller than an atom

• Note
• The nucleus consists of protons and neutrons
• Nucleus is positively charged. Why?
• Electrons move around very rapidly. They tend to
  occupy layers or shells at different distances
  from the nucleus.

• Atoms - made up of subatomic particles

positively charged
proton
neutron
neutral
negatively charged
electron
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Subatomic Particles
positively charged
proton
neutron
Particle Symbol Relative Mass Charge
Proton p 1 1
Neutron n 1 0
Electron e- 1/1836 1-
neutral
electron
negatively charged
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Thinking Time
Particle Symbol Relative Mass Charge
Proton p 1 1
Neutron n 1 0
Electron e- 1/1836 1-
Why is the term "relative mass" used rather than
just mass?
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Thinking Time

• Hints
• Mass of proton 1.6710-27 kg
• Mass of neutron 1.6710-27 kg
• Mass of electron 9.1110-31 kg

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Thinking Time

• Mass of proton, neutron and electron are too
  small and inconvenient to work with.
• By using relative mass, we do not have to
  remember the exact value of the various masses.

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Moving on

• The Periodic Table

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The Periodic Table
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Counting protons

• Proton Number
• The number of protons in an atom is called the
  proton number. Proton number is also known as the
  Atomic Number.

From Periodic Table
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Counting protons neutrons

• Nucleon Number
• Nucleon number is the number of protons and
  neutrons in the nucleus of an atom. Nucleon
  number is also called the Mass Number.

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Nucleon Number

• Nucleon (Mass) number
• number of protons number of neutrons

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• Carbon atom in symbol form C.
• Can also be written as carbon-12.

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6
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Question

• How many protons, electrons, and neutrons are
  there in a C atom?
• 6 protons, 6 electrons and 6 neutrons.

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Thinking Time

• What is the proton number and nucleon number of
  an atom of Cu?
• Proton number 29 
• Nucleon number 64

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Thinking Time

• What is the atomic number and mass number of an
  atom of Ca?
• Atomic number 20 
• Mass number 40

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Thinking Time

• Using the periodic table, identify
• the mass number of an atom of bromine
• (b) the atomic number of an atom of boron
• (c) the proton number of an atom of platinum
• (d) the nucleon number of an atom of niobium

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Thinking Time

• Using the periodic table, identify
• the mass number of an atom of bromine - 80
• (b) the atomic number of an atom of boron - 5
• (c) the proton number of an atom of platinum -
  78 
• (d) the nucleon number of an atom of niobium - 93

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Complete the table
Element H Na S
Number of protons
Number of electrons
Number of neutrons
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Complete the table
Element H Na S
Number of protons 1 11 16
Number of electrons 1 11 16
Number of neutrons 0 12 16
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Back to the Atomic Model

• The centre of an atom is called the nucleus
  which contains the protons and neutrons.

protons
nucleus
neutrons
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The Atomic Model

• The electrons in an atom are arranged in shells
  (orbits) at different distances from the nucleus.
• Note Shells are also called energy levels.

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The Atomic Model
Each shell can hold a certain maximum number of
electrons.

(a) 1st shell - 2 electrons
(b) 2nd shell - 8 electrons
(c) 3rd shell - 8 electrons (1st 20 elements
only)
Advanced For elements after calcium in the 4th
period, their third shell can hold up to 18
electrons.
1st shell
2nd shell
electron
3rd shell
4th shell
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Question

• An atom can be described as an electrically
  neutral entity made up of a positively charged
  nucleus at its centre with negatively charged
  electrons moving around the nucleus.

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Question

• An atom can be described as an electrically
  neutral entity made up of a positively charged
  nucleus at its centre with negatively charged
  electrons moving around the nucleus.
• (a) Why is the atom electrically neutral?
• Number of electrons number of protons. Equal
  positive and negative charges
• (b) Why is the nucleus positively charged?
• The nucleus contains protons and neutrons.
  Protons are positively charged while neutrons are
  electrically neutral.

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Differentiating different elements

• How do I differentiate the atoms of one element
  from the atoms of another element?
• All atoms of the same element have the same
  number of protons while those of different
  elements contain different number of protons.

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C
Na
vs
6
11
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What are Isotopes?

• Isotopes are atoms of the same element with
  different numbers of neutrons.
• -gt same proton number, different nucleon number
• E.g. carbon has 3 isotopes

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Electron Arrangement

• Nitrogen-14 atom has 7 electrons

• Key
• - electron
• p - proton
• n - neutron

7 p 7 n
Note full electronic configuration of an atom
shows the arrangement of electrons in different
shells.
Drawing the full electronic configuration
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Electron Arrangement

• Nitrogen-14 atom has 7 electrons

• Key
• - electron
• p - proton
• n - neutron

7 p 7 n
shows arrangement of electrons in different
shells.
Writing the electronic configuration 2.5
2nd shell
1st shell
separate the 2 shells
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Electron Arrangement

• Argon-40 atom has 18 electrons

• Key
• - electron
• p - proton
• n - neutron

18 p 22 n
electronic configuration of 2.8.8
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Valence Shell

• Valence shell - farthest occupied shell from the
  nucleus
• Valence electron - electron in the valence shell

7 p 7 n
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Valence Shell

• Note only valence electrons are involved in
  chemical reactions.

7 p 7 n
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Outer electronic structure

• only valence electrons are drawn

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Formation of Ions

• During chemical reactions, some atoms might
  lose/gain electron(s). Atom becomes an ion
  (charged particle) when it gains or loses
  electron(s).

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Question

• Why does an atom become a charged particle when
  it gains or loses electron(s)?
• An atom is electrically neutral because number
  of electrons number of protons (equal positive
  and negative charges).
• When it gains or loses electron(s), the positive
  and negative charges are not balanced.
  Therefore, the atom becomes a charged particle.

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Formation of cations

• When an atom loses one or more electrons, it
  becomes a positively charged particle called
  cation.

Lithium atom (Li) 3 electrons 3 protons Net
charge 0
Lithium ion (Li) 2 electrons 3 protons Net
charge 1
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Formation of anions

• When an atom gains one or more electrons, it
  becomes a negatively charged particle called
  anion.

Fluorine atom (F) 9 electrons 9 protons Net
charge 0
Fluoride ion (F-) 10 electrons 9 protons Net
charge -1
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Question for Thought

• Why do atoms become ions?
• To obtain a full valence shell
• To obtain the same electronic structure of a
  noble gas so as to be stable. (Note this will be
  covered under Chemical Bonding)

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Fill up the blanks
Charge of ion Element Name of ion Symbol of ion No. of electron gained No. of electron lost
Oxygen Sulfur Oxide Sulfide O2- S2-
Fluorine Chlorine Fluoride Chloride F- Cl-
Hydrogen Lithium Sodium Potassium Hydrogen Lithium Sodium Potassium H Li Na K
Beryllium Magnesium Calcium Copper Iron Beryllium Magnesium Calcium Copper (II) Iron (II) Be2 Mg2 Ca2 Cu2 Fe2
Aluminium Iron Aluminium Iron (III) Al3 Fe3
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Fill up the blanks
Charge of ion Element Name of ion Symbol of ion No. of electron gained No. of electron lost
-2 Oxygen Sulfur Oxide Sulfide O2- S2- 2
-1 Fluorine Chlorine Fluoride Chloride F- Cl- 1
1 Hydrogen Lithium Sodium Potassium Hydrogen Lithium Sodium Potassium H Li Na K 1
2 Beryllium Magnesium Calcium Copper Iron Beryllium Magnesium Calcium Copper (II) Iron (II) Be2 Mg2 Ca2 Cu2 Fe2 2
3 Aluminium Iron Aluminium Iron (III) Al3 Fe3 3
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Questions

• Do metals generally form cations or anions?
• cations
• Do non-metals generally form cations or anions?
• anions

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The Periodic Table

• Scientists have classified all discovered
  elements into a chart called the Periodic Table

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The Periodic Table

• In the Periodic Table, elements are arranged in
  order of increasing proton (atomic) number and
  are classified according to Groups and Periods.

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Vertical Row Group
Elements in the same group have similar chemical
properties and will undergo the same type of
chemical reactions
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Horizontal Row Period
As you move across a period, the properties of
the elements will change gradually from metallic
to non-metallic
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Group

• Groups are numbered from I to VII and then 0

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Group
Transition metals
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Group

• Elements in the same group have similar chemical
  properties and will undergo the same type of
  chemical reactions.

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Elements in the Periodic Table
Li Na K Rb Cs Fr

• Group I Alkali Metals
• Lithium, Sodium, Potassium, Rubidium, Cesium,
  Francium.
• Metals and solid at room temperature.
• Very reactive.

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Elements in the Periodic Table
Be Mg Ca Sr Ba Ra

• Group II Alkaline Earth Metals
• Beryllium, Magnesium, Calcium, Strontium, Barium,
  Radium.

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Elements in the Periodic Table
B Al Ga In Tl

• Group III
• Boron, Aluminum, Gallium, Indium, Thallium
• Except B, Group III elements are all metals.
• B is a metalloid.

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Elements in the Periodic Table
C Si Ge Sn Pb

• Group IV
• Carbon, Silicon, Germanium, Tin, Lead
• Carbon is a non-metal.
• Si and Ge are metalloids.
• Sn and Pb are metals.
• A metalloid is an element that has some of the
  physical characteristics of a metal but some of
  the chemical characteristics of a non-metal.

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Elements in the Periodic Table
N P As Sb Bi

• Group V
• Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth.
• Non-metals (N, P) to metalloids (As, Sb) to
  metals (Bi).

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Elements in the Periodic Table
O S Se Te Po

• Group VI
• Oxygen, Sulfur, Selenium, Tellurium, Polonium.
• Non-metals (O, S, Se) to metalloids (Te) to
  metals (Po).

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Elements in the Periodic Table
F Cl Br I At

• Group VII the Halogens
• Fluorine, Chlorine, Bromine, Iodine, Astatine.
• All non-metals.

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Elements in the Periodic Table
He Ne Ar Kr X Rn

• Group 0 the Noble Gases
• Helium, Neon, Argon, Krypton, Xenon, Radon.
• Least reactive elements.
• Also known as inert gases, or rare gases.

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Elements in the Periodic Table

• The Transition Elements
• All metals

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Period
1st period
2nd period
3rd period
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Fill up the blanks.
Element Proton number Number of electrons in Number of electrons in Number of electrons in Number of electrons in Electronic configuration Period Group
Element Proton number 1st shell 2nd shell 3rd shell 4th shell Electronic configuration Period Group
H 1
He 2
Li 3
Be 4
B 5
C 6
N 7
O 8
F 9
Ne 10
Na 11
Mg 12
Al 13
Si 14
P 15
S 16
Cl 17
Ar 18
K 19
Ca 20
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Fill up the blanks.
Element Proton number Number of electrons in Number of electrons in Number of electrons in Number of electrons in Electronic configuration Period Group
Element Proton number 1st shell 2nd shell 3rd shell 4th shell Electronic configuration Period Group
H 1 1 1 1 -
He 2 2 2 1 0
Li 3 2 1 2.1 2 I
Be 4 2 2 2.2 2 II
B 5 2 3 2.3 2 III
C 6 2 4 2.4 2 IV
N 7 2 5 2.5 2 V
O 8 2 6 2.6 2 VI
F 9 2 7 2.7 2 VII
Ne 10 2 8 2.8 2 0
Na 11 2 8 1 2.8.1 3 I
Mg 12 2 8 2 2.8.2 3 II
Al 13 2 8 3 2.8.3 3 III
Si 14 2 8 4 2.8.4 3 IV
P 15 2 8 5 2.8.5 3 V
S 16 2 8 6 2.8.6 3 VI
Cl 17 2 8 7 2.8.7 3 VII
Ar 18 2 8 8 2.8.8 3 0
K 19 2 8 8 1 2.8.8.1 4 I
Ca 20 2 8 8 2 2.8.8.2 4 II
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8 valence e-
1 valence e-
number of valence electrons for each element
group number
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Group I
1 valence e-
Electronic configuration 2.1
elements with similar electronic configurations
have similar chemical properties elements in the
same group have similar chemical properties
Electronic configuration 2.8.1
Electronic configuration 2.8.8.1
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Group I Reactivity
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Metals vs Non-metals
Non-metals
Metals
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Non-metals
Metals
Across the period, the properties of elements
change from metallic to non-metallic.
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Periodic Table An organised table that consists
of all the elements discovered.
Non-metals
Metals
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Periodic Table An organised table that consists
of all the elements discovered.
Non-metals
Metals
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Charges on ions
Charges on the ions formed are related to the
group number and number of valence electrons.
Element Na Mg Al Si P S Cl Ar
Group number I II III IV V VI VII 0
Formula of ion Na Mg2 Al3 - P3- S2- Cl- -
e- gain/lost 1 2 3 3 2 1
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Charges on ions
Element Na Mg Al Si P S Cl Ar
Group number I II III IV V VI VII 0
Formula of ion Na Mg2 Al3 - P3- S2- Cl- -
e- gain/lost 1 2 3 3 2 1

• Metal atoms lose their valence electrons to form
  cations with charges corresponding to their group
  number.
• Non-metal atoms gain electrons to form anions.
  The charges on the anions corresponding to the
  number of electrons gained to fill their valence
  shells with eight electrons.

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Try this!

• Draw a labelled diagram to show the full
  electronic configuration in an atom of
• (i) S

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Try this!

• Draw a labelled diagram to show the full
  electronic configuration in an atom of
• (ii) Ca