Lesson Notes By Weeks and Term - Senior Secondary 1

Chemical combinations I

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Term: 2nd Term

Week: 1

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:       

Subject:      Chemistry

Topic:-       Chemical combinations I

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. State the first 20 elements on the periodic table and their symbols
  2. Discuss the electronic configuration of atoms
  3. List and explain the types of strong bonds

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S ACTIVITY

STEP 1

INTRODUCTION

The teacher reviews the previous lesson on particulate nature of matter

Students pay attention

STEP 2

EXPLANATION

He states the first 20 elements on the periodic table and their symbols. He further discusses the electronic configuration of atoms

 

Students pay attention and participates

STEP 3

DEMONSTRATION

He lists and explains the types of strong bonds

Students pay attention and participate

STEP 4

NOTE TAKING

The teacher writes a summarized note on the board

The students copy the note in their books

 

NOTE

CHEMICAL COMBINATIONS
ELECTRONIC CONFIGURATION OF ATOMS

This is the arrangement of electrons in energy levels around an atomic nucleus. This can be expressed by the following models

  1. Shell atomic model
  2. Spdf notation or Quantum mechanical model

 

SHELL ATOMIC MODEL

This may be expressed by indicating the number of electrons in each shell beginning with the first

Example

          K      L       M      N

 

17Cl  2       8       7

 

20Ca 2       8       8       2

 

SPDF NOTATION

This follows Aufbau principle which states that in the building up of atoms, electrons enter into orbitals in order of increasing energy.

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p The minimum number of electrons for each sub orbital are as follows s=2

p=6

d= 10

f= 14

Example

17Cl = 1s2 2s2 2p6 3s2 3p5

20Ca = 1s2 2s2 2p6 3s2 3p6 4s2

 

PERIODIC TABLE

Brezelius in 1814 proposed the modern symbols being used on the periodic table. This involved the use of the letter or letters of the name of the respective elements; which could be English name, Latin, Greek, or as obtained. This also involved using capital letter for the first letter of the alphabets for the name of the element or the first letter and any other letter within the letters of the name of the element.

The table below shows the first 30 elements of the periodic table

 

 

 

Hydrogen

H

 

Helium

He

 

 

 

Lithium

Li

 

Beryllium

Be

 

 

 

Boron

B

 

Carbon

C

 

 

 

Nitrogen

N

 

Oxygen

O

 

 

 

Fluorine

F

 

Neon

Ne

 

 

 

Sodium

Na

 

Magnesium

Mg

 

 

Aluminum

Al

 

Silicon

Si

 

 

Phosphorus

P

 

Sulphur

S

 

 

Chlorine

Cl

 

Argon

Ar

 

 

Potassium

K

 

CHEMICAL COMBINATION

During a chemical reaction valence electrons are exchanged. Some of the strong bonds that take place are

  1. Electrovalent bond (Ionic Bond) is the transfer of electron during a chemical reaction. An element donates while another one accepts for the bonding to take place

Metallic ion donates electron while acidic radical accepts the electron. This is done with the view to obey the octet or duplet configuration of their outermost shell and is thus held together by a strong electrostatic force of attraction. i.e

Sodium atom loses electron to become positively charged sodium ion

Na0   Na+ + e-

On the other hand chlorine atom gains the lost electron to become negatively charged ion.

Clo + e- --à Cl-

The complete reaction is written as

Na+ + Cl- -à Na+ Cl-

  1. COVALENT BOND involves sharing of the bonding electrons donated by the atoms involved in the chemical bonding process. This occurs when elements of relative electro negativity pair together. Molecules are formed.

There is no electrostatic force between the combining atoms,

DIFFERENCES BETWEEN ELECTROVALENT AND COVALENT COMPOUND

PROPERTY

Electrovalent

Covalent

Melting point

Compound High ;more than 2500C

Compound Low; less than 2500C

Boiling point

High ; more than 5000C

Low less than 5000C

Electrical Conductivity

Good conductor in molten or aqueous form

Usually non conductor

Solubility in water

Usually soluble

Usually insoluble

Solubility in organic solvent

Usually insoluble

Usually soluble

 

 

  1. COORDINATE COVALENT BOND (DATIVE BOND) this type of bond involved the sharing of a pair of electron called “LONE PAIR ELECTRON” donated by only one of the reacting atoms

 

  1. METALLIC BOND this is a strong force of attraction created by formation of electron cloud as a result of the valence electron in the positive nuclei of metals

 

EVALUATION:    1. State the first 20 elements of the periodic table and                                    their symbols

2. Define electronic configuration. What is the electronic                    configuration of 20Ca using the shell atomic model?

3. Explain

  1. Electrovalent bonds
  2. covalent bonds
  3. coordinate covalent bonds
  4. metallic bonds

4. Highlight three differences between electrovalent and                    covalent bonds

5. Complete the following table

Particles

number of

Number of

Number of

Mass number

 

Neutrons

Electrons

Protons

 

W2+

12

 

 

24

X2-

 

 

8

16

Y

 

13

 

27

Z

12

11

 

 

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively