ELEMENTS IN A PERIOD

PERIODIC TABLE OF ELEMENTS (PG 72)

Period 3 elements – Na, Mg, Al, Si, P, S, Cl and Ar

ELEMENTS IN PERIOD 3 AND THE ELECTRON ARRANGEMENTS IN ALL

ELEMENTS IN PERIOD 3.

Element of period 3

Na Mg Al Si P S Cl Ar

Electron arrangement

2.8.1 2.8.2 2.8.3 2.8.4

2.8.5

2.8.6

2.8.7

2.8.8

+ e-e-

e-

e-e-

e- e-

e-e-

e-e-

2.8.1

+ e-e-

e-

e-e-

e-e-e-e-

e-e-

2.8.8

e-e-

e-e-

e-e-

e-+ e-e-

e-

e-e-

e- e-

e-e-

e-e-

2.8.4

e-

e-

e-

PROPERTIES OF ELEMENTS IN PERIOD 3

Element of period 3

Na Mg Al Si P S Cl Ar

Proton number

11 12 13 14 15 16 17 18

Electron arrangement

2.8.1 2.8.2 2.8.3 2.8.4

2.8.5

2.8.6

2.8.7

2.8.8

Electronic structure

Atomic radius (pm)

186 160 143 118 110 104 100 94

Physical state at room temperature

Solid Solid Solid Solid

Solid

Solid

Gas Gas

Electronegativity

0.9 1.2 1.5 1.8 2.1 2.5 3.0 -

THE CHANGES IN THE PROPERTIES OF ELEMENTS

ACROSS PERIOD 3

• THE PHYSICAL STATE OF ELEMENTS IN PERIOD 3 ARE SOLIDS EXCEPT CHLORINE AND ARGON WHICH ARE GASES.

• ATOMIC RADIUS OF ELEMENTS DECREASES DUE TO INCREASING NUCLEI ATTRACTION ON THE VALENCE ELECTRONS.

• ELECTRONEGATIVITY OF ELEMENTS INCREASES DUE TO INCREASING NUCLEI ATTRACTION ON THE VALENCE ELECTRONS AND THE DECREASE IN ATOMIC SIZE.

THE CHANGE OF PROPERTIES OF THE OXIDES OF ELEMENTS

ACROSS PERIOD 3

• SODIUM AND MAGNESIUM FORM BASIC METAL OXIDES.

• ALUMINIUM FORM AMPHOTERIC OXIDE. [AN AMPHOTERIC OXIDE CAN REACT WITH BOTH ACIDS AND BASES TO FORM SALTS AND WATER].

• SILICON, PHOSPHORUS, SULPHUR AND CHLORINE FORM ACIDIC NON-METAL OXIDES.

THE ACID-BASE PROPERTIES OF THE OXIDE

OF PERIOD 3 ELEMENTS

OxideObservation

InferenceWith water

pH Value

With NaOH With HNO3

Na2O Soluble. Forms

colourless solution

13 - 14 Insoluble Soluble. Forms colourless solution

Strong base.Strong alkali.

MgO Slightly soluble.

Colourless solution

8 - 9 Insoluble Soluble. Forms colourless solution

A basic oxide.Weak alkali.

Al2O3Insoluble 7 Soluble.

Forms colourless solution

Soluble. Forms colourless solution

An amphoteric oxide, with acidic

and bacic properties.

SiO2Insoluble 7 Soluble.

Forms colourless solution

Insoluble An acidic oxide.

THE ACID-BASE PROPERTIES OF THE OXIDE OF PERIOD 3 ELEMENTS

OxideObservation

InferenceWith water pH Value With NaOH

With NH3

P4O10Soluble. Forms

colourless solution

2 - 3 Soluble. Forms

colourless solution

Insoluble An acidic oxide.

SO2Soluble. Forms

colourless solution

2 - 3 Soluble. Forms

colourless solution

Insoluble Form an acid.An acidic oxide.

Cl2O7Soluble. Forms

colourless solution

1 Soluble. Forms

colourless solution

Insoluble Strong acid formed.

An acidic oxide.

CONCLUSION

The oxide of elements in period 3 change from basic to amphoteric and then to an acidic nature as we go across the period towards the right.

PREDICT THE CHANGES IN THE PROPERTIES OF ELEMENTS ACROSS OTHER PERIODS

• THE ELEMENTS CHANGES FROM:• STATE - SOLID TO GAS

• METAL TO NON-METAL

• CONDUCTOR TO

NON-CONDUCTOR

• THE FOLLOWING PROPERTIES DECREASES FROM LEFT TO RIGHT:• ATOMIC SIZE

• MELTING POINTS

• BOILING POINT

• THE FOLLOWING PROPERTIES INCREASE FROM LEFT TO RIGHT:• PROTON NUMBER

• THE NUMBER OF VALENCE ELECTRON

• ELECTRONEGATIVITY

SEMI METALS @ METALLOID• SEMI-METALS OR METALLOIDS ARE WEAK

CONDUCTORS OF ELECTRICITY.

• SEMI-METALS SUCH AS SILICON AND GERMANIUM ARE USED AS SEMICONDUCTORS.

• SEMICONDUCTORS ARE USED TO MAKE DIODES AND TRANSISTORS.

• DIODES AND TRANSISTORS ARE USED TO MAKING OF MICROCHIPS.

• SEMICONDUCTORS ENABLES US TO SURF INTERNET AND WATCH TELEVISION.

USES OF SEMI METALS IN INDUSTRY

Uses of semi metals