Chapter 4 Periodic Table of Elements

4.1 Analysing the Periodic Table of Elements4.2 Analysing Group 18 elements4.3 Analysing Group 1 elements4.4 Analysing Group 17 elements4.5 Analysing elements in a period4.6 Understanding transition elements.4.7 Appreciating the existence of elements and their compounds

4.1 Analysing the Periodic Table of Elements

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.

Example: to show the relationship elements in Periodic Table

Element Li Ca P OElectron arrangement of atom 2.1 2.8.8.

22.8.5 2.6

Number of valence electrons 1 2 5 6Group 1 2 15 16Number 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

Exercises 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?

4.2 Analysing Group 18 elements

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 propertiesLow melting and boiling points.

Inert which means chemically unreactive, because all elements in Group 18 has stable electron arrangement.

Colourless gases at room temperature.

Group 18 Elements Physical Properties

Helium, He2 [ 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, Ne2.8

Argon, Ar2.8.8

Kripton, Kr2.8.18.8

Xenon2.8.18.18.8

Radon2.8.18.32.18.8

[Oktet electron arrangement]

Uses of group 18 elementsNoble Gas Uses

Helium Fill weather balloons/airships/aircraft tyresLighter than air; does not burn

Argon Fill electric bulbsProvides inert atmosphere & protects filament from oxidation in air

Neon Neon lightsAs electric currents passed through neon gas to give a orange-red glow

Krypton Fill fluorescent light bulbs Xenon Used in making electron tubesRadon Small amounts of radon are sometimes used

by hospitals to treat some forms of cancer

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

4.3 Analysing Group 1 elements

Chemical Properties1. Most active metals, only found in

compounds in nature2. 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 electron4. Form +1 ion by losing that valence

electron5. Form oxides like Na2O, Li2O, K2O

Changes in physical propertis going down the group

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.

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.

Changes in chemical propertis going down the group

4.4 Analysing Group 17 elements 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 properties1. 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

Chemical properties1. 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.

4.5 Analysing elements in a period 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 numberElectron arrangement

Atomic radius 186

160

143 118 110 104 100 94

Physical state solid gasElectronegativity

0.9 1.2 1.5 1.8 2.1 2.5 3.0 -

4.6 Understanding transition elements.

LETS DO EXERCISES !!!