Topic 12 - Periodicity

Question 1

What is Periodicity

Answer 1

Recurrence of similar properties at regular intervals when elements arranged in increasing atomic number

Question 2

Periodicity in one period

3 types

Answer 2

Metals Semi-metals Non-metals
Giant MeTalLic Structure Giant Covalent Structure Simple Molecular Structure
MEtAllic Bond Covalent Bond

Question 3

Graph of Periodicity of Melting point

Answer 3

Group 4: C Si at Maxima
- Giant Covalent structure

Mg = Al
- Repulsion of 3 electrons - Weakens bond of Al

S>P>Cl
- Molecular size

Increases from Gp 1 to Gp 3
- More Electrons and +ve Charged ions

Decreases from Gp 5 to Gp 0
- Molecular Size

Question 4

Boron Structure

Answer 4

Giant Covalent Structure

Boron is a Semi Metal

Question 5

Breaking of Metallic bonds and Covalent Bonds to Melt the substance
Difference

Answer 5

Metallic bonds - A part of bonds
Covalent bonds - Most of the bonds

Ergo - Mp Covalent > Mp Metallic

Question 6

Graph of Relative Electrive Conductivity

Answer 6

Al Be - Peak

Gp 1 < Gp 3
- More delocalized e

Si B - low

• Semi-metals
• no delocalized e

Gp 5 to Gp 0

• Simple molecular
• No delocalized e or mobile ions

Question 7

Periodicity of Oxides from Na to Cl ×4

Answer 7

Basic: 11 12 Amphoteric: 13 Acidic Oxides: 14 15 16 17

Giant Ionic Giant Covalent Simple Molecular

Ionic Bonds Covalent bonds

White solid Colourless g/l: 16 Orange g/l: 17

Question 8

Structure difference related to electronegativity

Answer 8

Na < Cl electronegative
Na lose e Ionic
Cl shares e Covalent

Question 9

Basic Oxides
Which
Reactions

Answer 9

Na2O
MgO

With H2O - NaOH Mg OH2
With acid - H2O + Na Salt MgOH2 slightly soluble -

Question 10

Amphoteric Oxides
Which
Reaction

Answer 10

Al2O3

With H2O - Insoluble
With Acid - Al2O3 + 6H+ -> 3H2O + Al³
With Alkali - Al2O3 + 2OH- + 3H2O -> 2Al(OH)4-

Question 11

Acidic Oxides
Which
Reaction

Answer 11

w/H2O          w/alkali
SiO2        insoluble      SiO3 2-
P4O10    H2PO4       
SO2         H2SO3          SO3 2-
Cl2O        HClO

Question 12

Transition Metal Electronic Configuration

Answer 12

Sc 2 8 9 2
Ti 2 8 10 2
V 2 8 11 2
Cr 2 8 13 1

Question 13

Transition Metal Characteristics

Answer 13

Next inner shell can receive more e-

High Melting Point
High density
Hard + Right
- Both outermost shell and Next inner shell e- can be Delocalized
-- Stronger metallic bond

Similar Chemical Properties
- either 1 or 2 outermost e-

Question 14

Transition Metal Main Group Metal

Comparison

Answer 14

Transition Main Group

• Coloured aq ions - Colourless
• Variable Oxidative State - One Oxi State
• Catalytic Prop - No Catalytic Prop