Sir Antoine Lavoisier (1743 1794)

First to classify elements into groups

It is arranged into 4 different group as shown in table

In his table, elements are classified into metals and non-metals

It is not a good periodic table as substances such as heat, light

and sun were included in his grouping as these are not element

Still, his contribution towards the periodic table is treasured as

hes the 1st one to start grouping element

Johann W. Dobereiner ((1780 1849)

Invented a classifying method named triad where 3 elements are

grouped under the same category base on their relative mass.,

where the median is the average of the highest and lowest value

Weakness : The elements that can be categorized were very

limited.

Advantage : scientist begin to realize that there were relationship

between the elements with the same properties and the relative

mass of the elements involved.

John Newland (1837 1898)

Arrange the elements that were discovered during that time in a horizontal method in ascending order of their atomic masses. Each row consisted of 7 elements

He believed that elements with the same properties will repeat in every 8th elements in his periodic table. This pattern is similar to octave notes in the music score. That is why its called octaves law

Still, it is not enough as everything went wrong after the 17th elements (from H to Ca is true)

Still it is a very large contribution toward the modern periodic table as people now learned how to arrange the periodic table using atomic mass and its repeating theoriesmass and its repeating theories

Lothar Meyer (1830 1895)

Plotted a graph of atomic volume against atomic mass for all known

elements at that time.

Realize that elements with the same chemical properties occupied

the same relative positions on the curve.

Highlighted the pattern of the graph from the elements has a trend

in the tendencies of similarity of the substance

Dmitri Mendeleev (1834 1907)

Shown properties of elements changed periodically with atomic mass

He grouped elements with the same properties placed in the same vertical column

He also left some space for elements which is yet discovered at that time

Using the emptied space, the properties of the undiscovered element were predicted and it is later found similar to the properties predicted by him.

Separate elements which cannot be placed normally into his Separate elements which cannot be placed normally into his table as transition elements

His table are basis of todays Modern periodic table

J. G. Moseley (1887 1915)

Using X-Ray method to determine the position of elements in

Periodic Table. He then plotted a graph of square root of the

frequency of the X-ray from elements against proton

numbers. A straight line is obtained.

From the information, hes able to categorise the periodic

table similar to the Modern Periodic Table. He also

successfully proved Mendeleevs prediction of the empty

element.element.

His achievement had help in developing the Modern Periodic

Table today

A periodic table of partial ground-state electron configurations

Group 18 element (Noble Gas)

Our air consists of about 1% of noble gases. These gases are

inert(non-reactive) gases.

In the Modern periodic Table the Group 18s elements are

Helium Neon Argon

Krypton Xenon Radon

Below shows some physical properties of the elements

Element He Ne Ar Kr Xe Trend

Proton

number2 10 18 36 54

Atomic

radius

(nm)

0.050 0.070 0.094 0.109 0.130

Increase when goes down to

group. More shell is required when

more electron filling in, thus

causing the atomic radius to

increase.

Melting Monoatomic gases of noble gas Melting

point

(oC)

-270 -248 -189 -156 -112

Monoatomic gases of noble gas

have very weak Van Der Waals

forces between the atoms,

resulting the amount of heat

required to break the forces

between the atoms are little.

Generally, b.p and m.p increase

when goes down the group.

Boiling

point

(oC)

-269 -246 -186 -152 -107

Physical

stateGas Gas Gas Gas Gas

Since the boiling point is below

room temperature, so it exist as

gas

Element Proton numberElectron

arrangement

Helium (He) 2

Neon (Ne) 10

Argon (Ar) 18

Krypton (Kr) 36 2.8.18.8

2

2.8

2.8.8

Xenon (Xe) 54 2.8.18.18.8

From the electron arrangement, we can tell that, all the

Group 18 gases have achieved octet states. Thus, these

gases are very stable and unreactive. The octet

arrangement of the noble gas also allows them to exist as

monoatom, as they are already stable on its own.

Application of noble gas in our daily life

Helium

(He)

Use as weather balloon and airship

Use by divers where helium is mixed with oxygen gas to use in

ocean diving

Use by physicist in measuring low temperature thermometer.

Neon

(Ne) Use in commercial / advertisement boards.

Argon

(Ar)

Fill electrical bulbs

Support welding process (prevent air to react with the hot metal)(Ar) Support welding process (prevent air to react with the hot metal)

Krypton

(Kr)

Use in flash light in camera and DV

Use in laser to repair the retina of our eyes

Radon

(Rn) Kill cancerous cell

Group 1 elements

Group 1 are also known as alkali earth metal as it is an

alkali substance

The elements of Group 1 are

Lithium (Li) Sodium (Na) Potassium (K)

Rubidium (Rb) Caesium (Cs) Francium (Fr)

Below are some physical properties of Group 1 elements Below are some physical properties of Group 1 elements

Element

sLi Na K Rb Cs

Trend

Proton

number3 11 19 37 55

All alkali metals are grey soft solid

with shiny surface. Since its soft,

its easily to cut alkali metal

Atomic

radius

(nm)

0.15 0.19 0.23 0.25 0.26

Increase when goes down to

group. More shell is required

when more electron filling in, thus

causing the atomic radius to

increase.

The intermolecular forces of Melting

point

(oC)

181 98 64 39 28

The intermolecular forces of

metal solid : metallic bonding;

Strength : how the free electrons

of metal are able to interact with

the nucleus of the atom. When

going down to group, metallic

bond decrease as the electrons

are getting further away from the

nucleus when the radius

gradually increase.

Boiling

point

(oC)

1347 890 774 689 677

Element Li Na K Rb Cs Trend

Proton

number3 11 19 37 55

Physical

stateSolid Solid Solid Solid Solid

Since the melting point of alkali

metal are all above room

temperature, so alkali metal exist

as solid.

Density

Even though alkali metals are

solid, some of them are actually Density

(g/cm3)0.53 0.86 0.97 1.53 1.88

solid, some of them are actually

less dense than water (Li, Na, K).

The mass / volume of Li, Na and

K are lower than 1.00Conducti

vity of

heat and

electricit

y

Good Good Good Good Good

Since its a metal usually it

conducts heat. As for electricity, it

has free mobile ion to move

around and conduct electricity.

Elements Lithium

(Li)

Sodium

(Na)

Potassium

(K)

Rubidium

(Rb)

Caesium

(Cs)

No. of

electrons3 11 19 37 55

Electron

arrangemen2.8.18.8.1 2.8.18.18.8.12.1 2.8.1 2.8.8.1

Reactive

Electroposi

tivity

Cation

formed

Reactivity increase when going down to Group 1

Electropositivity increase when going down to Group 1

Li+ Na+ K+ Rb+ Cs+

Since all Group 1 elements possessed the same number of

______________ so they exhibit similarity in terms of chemical

properties.

All Group 1 elements will ______ 1 electron away to achieve octet.

Reactiveness _______ as the electropositivity ________.

Electropositivity measures on how easy an atom release an

electron to become positively charges ion (cation). So, when

the distance between the outer-most electron and nucleus

increase, more ______ for the atom to release the outer-most

electron, thus it is more ____________

valance electron

donateincrease increase

easier

electropositiveelectron, thus it is more ____________electropositive

To study the chemical properties of Group 1 through

the reaction with water and oxygen.

Alkali metal become more reactive in their reaction

with water when goin down Group 1.

Type of alkali metal

Reactivity of alkali metal

Water and size of alkali metal

Lithium melted and

moved slowly at

random on the

surface of water

with plenty of fizz.

A colourless

solution is formed

Sodium melted

and moved rapidly

at random on the

surface of water

with hissing sound.

A colourless

solution is formed

Potassium melted

and moved very

fast at random on

the surface of

water and ignited

with a lilac flame,

gave out pop and solution is formed

which turn red

litmus red to blue

solution is formed

which turn red

litmus red to blue

gave out pop and

hissing sound. A

colourless solution

is formed which

turn red litmus red

to blue

2 Li (s) + 2 H2O (l) 2 LiOH (aq) + H2 (g)

2 Na (s) + 2 H2O (l) 2 NaOH (aq) + H2 (g)

2 K (s) + 2 H2O (l) 2 KOH (aq) + H2 (g)

This is due to the formation of the solution of metal hydroxide

which are alkaline

The reaction of potassium and sodium is too reactive, so its

too dangerous to be carried out by students

Alkali metal become more reactive in their reaction

with oxygen when going down Group 1.

Type of alkali metal

Reactivity of alkali metal

Oxygen gas and size of alkali Oxygen gas and size of alkali

metal

Lithium burned

slowly with red

flame. White fumes

which become a

white solid when

cooled to room

temperature, were

produced

Sodium burned

rapidly with a bright

yellow flame. White

fumes which

become a white

solid when cooled to

room temperature,

were produced

Potassium burned

very rapidly with a

lilac flame. White

fumes which

become a white

solid when cooled to

room temperature,

were produced

White solid

dissolved in water to

form colourless

solution that turned

red litmus paper to

blue colour.

White solid

dissolved in water to

form colourless

solution that turned

red litmus paper to

blue colour.

White solid

dissolved in water to

form colourless

solution that turned

red litmus paper to

blue colour.

4 Li (s) + O2 (l) 2 Li2O (s)

Li2O (s) + H2O (l) 2 LiOH (aq)

Yes, since all alkali metal has the same valence electron,

which is 1.

Lithium, sodium and potassium react similarly with oxygen. The

reactivity increase from Li , Na , K