1. The document discusses the organization of elements in the periodic table according to their proton number and electron configuration. 2. Elements are arranged in periods from Period 1 to 7 based on the number of electron shells, and in groups from 1 to 18 based on their chemical properties and number of valence electrons. 3. Elements within the same group have similar chemical properties because they have the same number of valence electrons.

2. 1. Elements in Periodic Table are arranged in an
increasing order of proton number.
2. Each vertical column of elements is called a
group, known as Group 1- Group 18.
3. Each horizontal rows of elements is called a
period, known as Period 1- Period 7.
4. Elements in same Group, has same chemical
properties.
5. Elements in same period because its arranged
occording same number of shell.

3. Element Li Ca P O
Electron arrangement of atom 2.1 2.8.8.2 2.8.5 2.6
Number of valence electrons 1 2 5 6
Group 1 2 15 16
Number of shells occupied with
electrons
2 4 3 2
Period 2 4 3 2
# For elements with 3 to 8 valence electrons,
The group number of an element
= number of valence elctrons + 10

4. 1. Element D has a proton number of 19.
where is element D located in the
Periodic Table?
2. An atom of elements X is located in
Group 18 and period 2 of the Periodic
Table. What is the electron arrangement
and proton number of atom X?

5. 1. Very useful in our daily lives. Make up
almost 1% in air.
2. Also known as Noble gases.
3. Noble gases are monoatomic.
Physical Properties Chemical properties
Low melting and boiling
points.
Inert which means chemically
unreactive, because all
elements in Group 18 has
stable electron arrangement.
Colourless gases at room
temperature.

6. Group 18 Elements Physical Properties
Helium, He
2 [ duplet electron arrangement] Low melting and boiling point
going down the group 18,
melting and boiling point
increases
BECAUSE
as the atomic size increases
going down the group,
the forces of attraction
between the atoms of element
become stronger,
thus more heat energy is
required to overcome the
stronger forces of attraction.
High melting and boiling point
Neon, Ne
2.8
Argon, Ar
2.8.8
Kripton, Kr
2.8.18.8
Xenon
2.8.18.18.8
Radon
2.8.18.32.18.8
[Oktet electron
arrangement]

7. Noble Gas Uses
Helium Fill weather balloons/airships/aircraft tyres
Lighter than air; does not burn
Argon Fill electric bulbs
Provides inert atmosphere & protects filament from
oxidation in air
Neon Neon lights
As electric currents passed through neon gas to give a
orange-red glow
Krypton Fill fluorescent light bulbs
Xenon Used in making electron tubes
Radon Small amounts of radon are sometimes used by
hospitals to treat some forms of cancer

8.  Physical Properties
1. Grey solid with shiny surface.
2. Softer and the density is lower
compare other metals.
3. Lower melting and boiling points
compare to other metals

9. 1. Most active metals, only found in
compounds in nature
2. React violently with water to form
hydrogen gas and a strong base:
2 Na (s) + H2O (l) 2 NaOH (aq) + H2(g)
3. 1 valence electron
4. Form +1 ion by losing that valence
electron
5. Form oxides like Na2O, Li2O, K2O

10. 1. Atomic size increases
because number of shells
increases.
2. Density increases because
the mass increases.
3. Melting and boiling points
decrease because when the
atomic size increases, the
attraction between nucleus
and valence electron
becomes weaker.

11. Reactivity of alkali metals
increases going down the
group,
- because the number of shells
increses,
- atomic size increases, and
- valence electron gets further
away from nucleus,
- so the strength of attraction
becomes weaker and
- valence electron easier to be
released.

12.  Also known halogen gases
 Poisonous elements
 Exist as diatomic molecules, eg, Cl2, F2, Br2, I2
 Must handle in fume chamber, wear
goggles and gloves.
Physical properties
1. Low boiling and melting points.
2. Going down group, at room temperature
physical changes from gas to liquid, then
to solid.
•Fluorine- paleyellow gas
•Chlorine- greenish yellow gas
•Bromine- reddish brown liquid
•Iodine- purplish black solid

13. 1. Halogens react with water to form two
acids.
Eg: Cl2 + H2O HCl + HOCl
2. Halogens gases react with hot iron to form
brown solid, iron(III) halides
Eg: 2Fe + 3Br2 2FeBr3
3. When down group 17, the atomic size
increase, outermost occupied atom get
futher from nucleus, so the strenght to
attract one electron become weaker and
causes reactivity decrease down the group.

14.  Elements across a period are changes in
properties.
# atomic radius decrease because increasing
nucleus attraction on valence electron
# electronegativity is strenght of atom to atract
electron towards nucleus.
Elements period 3 Na Mg Al Si P S Cl Ar
Proton number
Electron
arrangement
Atomic radius 186 160 143 118 110 104 100 94
Physical state solid gas
Electronegativity 0.9 1.2 1.5 1.8 2.1 2.5 3.0 -

16. LETS DO
EXERCISES !!!