1. Can you recall… What is Matter?
Matter is anything that has mass and takes up space.

2. What is matter made of?

3. 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.)

4. 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

5. Particles that make up of matter
Iron on Copper

6. What is an atom?
An atom is the smallest unit of an element, having the properties of that element.
Atom!
solid
liquid
gas

7. 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?

8. Let’s learn more about the ATOM

9. With nothing else inside?
Model of an Atom
Are atoms like solid balls?
With nothing else inside?

10. 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 (Rutherford–Bohr Model)
Bohr–Sommerfeld model (Refined Bohr Model)
Gryziński model (Free-fall Model)
Schrodinger model (Electron Cloud Model)

11. The Ever Changing Model…
Psy, psy, psy, psy, psy…
(Which model should I learn?)

12. Presenting to you…
electron
proton
neutron
nucleus
The Bohr Model

13. 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
nucleus
neutron
neutral
shell
negatively charged
electron

14. Subatomic Particles proton nucleus neutron electron positively charged
Symbol
Relative
Mass
Charge
Proton p 1 1+
Neutron n
Electron e-
1/1836 1-
neutral
electron
negatively charged

15. Thinking Time…
Particle
Symbol
Relative
Mass
Charge
Proton p 1 1+
Neutron n
Electron e-
1/1836 1-
Why is the term "relative mass" used rather than just mass?

16. Thinking Time… Hints… Mass of proton ≈ 1.67×10−27 kg
Mass of neutron ≈ 1.67×10−27 kg
Mass of electron ≈ 9.11×10−31 kg

17. 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.

18. Moving on…
The Periodic Table

19. The Periodic Table

20. 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…

21. 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.

22. Nucleon Number Nucleon (Mass) number =
number of protons + number of neutrons

23. Carbon atom in symbol form: C. Can also be written as carbon-12.6

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

25. Thinking Time…
What is the proton number and nucleon number of an atom of Cu?
Proton number: 29 
Nucleon number: 64

26. Thinking Time…
What is the atomic number and mass number of an atom of Ca?
Atomic number: 20 
Mass number: 40

27. 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

28. 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

29. Complete the table: Element H Na S Number of protons
Number of electrons
Number of neutrons

30. Complete the table: Element H Na S Number of protons 1 11 16
Number of electrons
Number of neutrons 12

31. Back to the Atomic Model…
The centre of an atom is called the nucleus which contains the protons and neutrons.
protons
nucleus
neutrons

32. 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.
protons
neutrons
nucleus
1st shell
2nd shell
3rd shell
4th shell
electron

33. 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

34. 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.

35. 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.

36. 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. 12 23 C vs Na 6 11

37. What are Isotopes?
Isotopes are atoms of the same element with different numbers of neutrons.
-> same proton number, different nucleon number
E.g. carbon has 3 isotopes: 12 6 C 13 6 C 14 6 C

38. Drawing the full electronic configuration
Electron Arrangement
Nitrogen-14 atom has 7 electrons
Key
- electron
p - proton
n - neutron
7 p
7 n
Drawing the full electronic configuration
Note: full electronic configuration of an atom shows the arrangement of electrons in different shells.

39. Writing the electronic configuration: 2.5
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
1st shell
2nd shell
separate the 2 shells

40. Electron Arrangement Argon-40 atom has 18 electrons
Key
- electron
p - proton
n - neutron
18 p
22 n
electronic configuration of 2.8.8

41. Valence Shell Valence shell - farthest occupied shell from the nucleus
Valence electron - electron in the valence shell
7 p
7 n

42. Valence Shell
Note: only valence electrons are involved in chemical reactions.
7 p
7 n

43. Outer electronic structure
only valence electrons are drawn
7 p
7 n
Key
- electron
p - proton
n - neutron

44. 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).

45. 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.

46. 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

47. 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

48. 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)

49. 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 H+
Li+
Na+ K+
Beryllium
Magnesium
Calcium
Copper
Iron
Copper (II)
Iron (II)
Be2+
Mg2+
Ca2+
Cu2+
Fe2+
Aluminium
Iron (III)
Al3+
Fe3+

50. 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 H+
Li+
Na+ K+ +2
Beryllium
Magnesium
Calcium
Copper
Iron
Copper (II)
Iron (II)
Be2+
Mg2+
Ca2+
Cu2+
Fe2+ +3
Aluminium
Iron (III)
Al3+
Fe3+ 3

51. Questions… Do metals generally form cations or anions? cations
Do non-metals generally form cations or anions?
anions

52. The Periodic Table
Scientists have classified all discovered elements into a chart called the Periodic Table

53. 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.

54. Vertical Row: Group
Elements in the same group have similar chemical properties and will undergo the same type of chemical reactions

55. Horizontal Row: Period
As you move across a period, the properties of the elements will change gradually from metallic to non-metallic

56. Group
Groups are numbered from I to VII and then 0

57. Group Alkali metals Noble gases Alkaline earth metals Halogens
Transition metals

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

59. Elements in the Periodic TableLi Na K Rb Cs Fr
Group I – Alkali Metals
Lithium, Sodium, Potassium, Rubidium, Cesium, Francium.
Metals and solid at room temperature.
Very reactive.

60. Elements in the Periodic TableBe Mg Ca Sr Ba Ra
Group II – Alkaline Earth Metals
Beryllium, Magnesium, Calcium, Strontium, Barium, Radium.

61. Elements in the Periodic TableAl Ga In Tl
Group III
Boron, Aluminum, Gallium, Indium, Thallium
Except B, Group III elements are all metals.
B is a metalloid.

62. Elements in the Periodic TableGe 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.

63. Elements in the Periodic TableAs Sb Bi
Group V
Nitrogen, Phosphorus, Arsenic, Antimony, Bismuth.
Non-metals (N, P) to metalloids (As, Sb) to metals (Bi).

64. Elements in the Periodic TableSe Te Po
Group VI
Oxygen, Sulfur, Selenium, Tellurium, Polonium.
Non-metals (O, S, Se) to metalloids (Te) to metals (Po).

65. Elements in the Periodic TableF Cl Br I At
Group VII – the Halogens
Fluorine, Chlorine, Bromine, Iodine, Astatine.
All non-metals.

66. Elements in the Periodic TableNe 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.

67. Elements in the Periodic Table
The Transition Elements
All metals Au Hg Pt Fe Cu Ti Rh Mn Zr V Cr Ni Zn Ag

68. Period 1st period 1st shell fully occupied 2nd period
2nd shell fully occupied
3rd period

69. Electronic configuration
Fill up the blanks.
Element
Proton number
Number of electrons in
Electronic configuration
Period
Group
1st shell
2nd shell
3rd shell
4th shell 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

70. Electronic configuration
Fill up the blanks.
Element
Proton number
Number of electrons in
Electronic configuration
Period
Group
1st shell
2nd shell
3rd shell
4th shell H 1 - He 2 Li 3
2.1 I Be 4
2.2 II B 5
2.3
III C 6
2.4 IV N 7
2.5 V O 8
2.6 VI F 9
2.7
VII Ne 10
2.8 Na 11
2.8.1 Mg 12
2.8.2 Al 13
2.8.3 Si 14
2.8.4 P 15
2.8.5 S 16
2.8.6 Cl 17
2.8.7 Ar 18
2.8.8 K 19 Ca 20

71. number of valence electrons for each element = group number

72. elements in the same group have similar chemical properties
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 –

73. Group I Reactivity

74. Metals vs Non-metals
Non-metals
Metals 74

75. Non-metals
Metals
Across the period, the properties of elements change from metallic to non‐metallic.

76. Periodic Table: An organised table that consists of all the elements discovered.
Non-metals
Metals 76

77. Periodic Table: An organised table that consists of all the elements discovered.
Non-metals
Metals 77

78. 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
Formula of ion
Na+
Mg2+
Al3+ -
P3-
S2-
Cl-
e- gain/lost 1 2 3

79. Charges on ions
Element Na Mg Al Si P S Cl Ar
Group number I II
III IV V VI
VII
Formula of ion
Na+
Mg2+
Al3+ -
P3-
S2-
Cl-
e- gain/lost 1 2 3
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.

80. Try this!
Draw a labelled diagram to show the full electronic configuration in an atom of (i) S

81. Try this!
Draw a labelled diagram to show the full electronic configuration in an atom of (ii) Ca