Thursday_26: Calculating Ar

• Chemistry
• Secondary Education

Pres_Template

CHEMISTRY 9

16 - Isotopes

state the 

A_r equation

use the A_r equation to calculate elements' relative atomic mass

reflect on my thinking and learning using the self-reflection checklist.

Daily Review

• Complete the table in your notebook.
• Use your pen to complete your task.

Sulfur

Chlorine

Argon

Potassium

Calcium

• Complete the table in your notebook.
• Use your pen to complete your task.

Sulfur

Chlorine

Argon

Potassium

Calcium

S

Cl

Ar

K

Ca

16

-16

+16

17

-17

+17

18

19

20

-18

-19

-20

+18

+19

+20

Starter

• Open your Google Classroom.
• Look for " I need to read this in advance.". 

• Open your Google Classroom.
• Look for " I need to read this in advance.". 

Main Lesson

Isotopes

Similarities

• same chemical characteristics
• appearance, so a sample of C-14 would look no different from C-12

Differences

• Neutrons within the nucleus and mass only
• Differences in mass affect physical properties such as density, boiling point, and melting point

Relative atomic mass

• A unit called the relative atomic mass (Ar) is used
• Relative atomic mass unit = 1/12th the mass of a carbon-12 atom

Relative atomic mass

• A unit called the relative atomic mass (Ar) is used
• Relative atomic mass unit = 1/12th the mass of a carbon-12 atom

• Imagine you have 90 balls with a mass of 200 g and 10 balls with a mass of 300 g. The average mass of the balls is given by:

• Imagine you have 90 balls with a mass of 200 g and 10 balls with a mass of 300 g. The average mass of the balls is given by:

• Imagine you have 90 balls with a mass of 200 g and 10 balls with a mass of 300 g. The average mass of the balls is given by:

Sample:

Pres_Template

CHEMISTRY 9

16 - Isotopes

state the 

A_r equation

use the A_r equation to calculate elements' relative atomic mass

reflect on my thinking and learning using the self-reflection checklist.

Practice Activity

Guided Practice: You do it together!

• Prepare your notebook and pen.
• Prepare the calculator of your device or a calculator.
• Look for the copy of the A_r worksheet in your notebook.
• Calculate the A_r of the given elements.
• Share your work with the class.

Plenary session

state the 

A_r equation

use the A_r equation to calculate elements' relative atomic mass

explain the difference between mass number and relative atomic mass