The document outlines a chemistry lesson focused on the atomic size of elements in the periodic table, emphasizing the trends in atomic size as one moves down groups and across periods. It details the educational objectives, group activities, and discussions aimed at helping students understand concepts like shell increase and nuclear charge. Various evaluation methods, including observations recorded in science diaries and review questions, are included to reinforce learning outcomes.

1. 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

2. 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

3. 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.

4. 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.

5. 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.