Loading....
Coupon Accepted Successfully!

 

General Characteristics of a Period

1. Valence Electrons
In a period, from left to right, the number of valence electron increases from 1 to 8.


2. Atomic Size
The atomic radius decreases while moving from left to right along a period. This is due to an increase in nuclear charge which tends to pull the electron closer to the nucleus and reduces the size of the atom.


3. Valency with respect to Oxygen
From left to right in a period, valency with respect to oxygen increases from 1 to 7.

 

Table: 5.4 Valence electron and valency with respect to hydrogen in first short period

Element

Lithium

Berylium

Boron

Carbon

Nitrogen

Oxygen

Fluorine

Property

  (Li)

 (Be)

 (B)

(C)

 (N)

(O)

(F)

Group

IA

IIA

IIIA

IVA

VA

VIA

VIIA

Valance electrons

1

2

3

4

5

6

7

Valency with respect to hydrogen

1

2

3

4

3

2

1

Example:

 

 

 

 

 

 

 

Hydride

LiH

 

BH3

CH4

NH3

H2O

HF

Chloride

LiCl

BeCl2

BCl3

CCl4

NCl3

Cl2O

ClF


4. Valency with respect to Hydrogen
Valency with respect to hydrogen increases from 1 to 4 and then decreases from 4 to 1 which is shown below in a tabular column.

 

Table 5.5 Valence electron and valency with respect to hydrogen in first short period

Element

Lithium

Berylium

Boron

Carbon

Nitrogen

Oxygen

Fluorine

Property

(Li)

(Be)

(B)

(C)

(N)

(O)

(F)

Group

IA

IIA

IIIA

IVA

VA

VIA

VIIA

Valance electrons

1

2

3

4

5

6

7

Valency with respect to hydrogen

1

2

3

4

3

2

1

Example

 

 

 

 

 

 

 

Hydride

LiH

 

BH3

CH4

NH3

H2O

HF

Chloride

LiCl

BeCl2

BCl3

CCl4

NCl3

Cl2O

ClF


5. Metallic Nature
In a period, from left to right, the metallic character gradually decreases. Therefore, in the extreme left of the periodic table are typical metals while on the extreme right of the periodic table are the typical non-metals.


6. Nature of Oxides
In a period, from left to right, the nature of oxide gradually changes from strongly basic to strongly acidic. This difference in the properties of oxides is one of the criteria used to classify as metals, non-metals and metalloids.


7. Diagonal relationship
It is the close similarity in properties of certain elements which are placed diagonally across in the periodic table.

 



The following pairs have a diagonal relationship: Lithium with magnesium, beryllium with aluminium, and boron with silicon.




Test Your Skills Now!
Take a Quiz now
Reviewer Name