Lesson Transcript

Curricular Objective

To identify the characteristic properties of elements through experiments, observations and discussions at the same time analyze the atoms and

realize its size variations in down the groups and along the periods.

Content Analysis

Facts and Concepts

A. Moving down the groups, the atomic size of atom increases

B. As the no of shells increases, atomic size also increases.

C. The biggest atom in each group is placed at the bottom.

D. Across the period, the positive charge of nucleus will increase from left to right.

E. Across the period, the number of shells remains constant.

F. Across the period, the biggest atom will remain at the left.

G. The size of Lithium is bigger than Hydrogen

H. Lithium has two shells while Hydrogen has only one shell.

I. The size of Lithium is larger than Beryllium.

Name of School : Standard : IX

Name of Teacher : Julie S.R. Strength :

Subject : Chemistry Date :

Unit : Periodic Table and Chemical Bond Duration : 45 Minutes

Topic : Atomic Size

Learning Objective

The pupil

remembers the above mentioned facts and concepts related to the topic atomic size.

develop understanding about the terms, facts and concepts related to it.

applies the knowledge about atomic size in new unfamiliar situation.

analyze the various situations related to atomic size and facts and concepts inherent in them.

evaluate various situations where atomic size is applicable.

develops components of creativity by constructing and visualizing various aspects related to atomic size

Strategies

- Group Activity

- Discussion

Pre-requisite

The students know the elements in each groups and periods.

Learning Aids

The Bohr model of elements in first group and second period (Still Model).

Process of Activity Response or Evaluation Orientation

We will start the class by asking the question whether all elements have

the same atomic size or not.

Group Technique

To divide the students into 4 groups such as 1,2,3 and 4

Presentation

Activity-1

To show the Bohr model of first group and second period elements in

the periodic table and discuss about, what changes happened in the sizes

of atoms from top to bottom in first group. Ask the students to write the

observations in science diary.

Points to be consolidated

- In group the number of shells will increase from top to bottom.

- Due to the increase of shells in each group from top to bottom,

the size of atom will also increase.

Activity-II

Discuss about the size of an atom varying across a period from left to

right based on Bohr model and ask the students to write their

observations in their science diary.

Points to be consolidated

- In period the nuclear charge will increase from left to right

- Due to the increase of nuclear charge in each period from left to

right, the size of atom will also increase.

Review

- What happens to the size of the atom when we are moving down the group?

- Where we can find the biggest atom in a group?

- What happens to the size of the atom when we are moving across the period?

- What happens to the charge of the nucleus of the atom when we are moving across a period?

Follow up Activity

Draw the Bohr model of atoms in group2 period 3 in periodic table and compare the variations in their atomic size.