Lesson Plan: Grade 9 Science Unit Title: Atoms and Elements Lesson Title: Determining number of protons, electrons, and neutrons from Atomic number and mass number– Lesson S1-2-04

Atomic Number

• # of protons

• # of electrons

•APE

• Atomic number = # of protons = # of electrons

•Always the smaller number

Atomic Mass number

• Mass of an atom of the element

• Sum of protons + neutrons

• Electrons are not included because they do not contribute significantly to the total mass

• Mass number – atomic number = # of neutrons

• Rounded to the nearest whole number

Magnesium

• Atomic number = 12

• Atomic mass number = 24

• Protons = 12

• Electrons = 12

• Neutrons = 12

Chlorine

• Atomic number = 17

• Atomic mass number = 35

• Protons = 17

• Electrons = 17

• Neutrons = 18

Atomic Number

Mass Number

Number of Protons

Number of Neutrons

Number of Electrons

Element

9 19 9 10 9 Fluorine

14 7

20 20

13 27

56 26

Atomic Number

Mass Number

Number of Protons

Number of Neutrons

Number of Electrons

Element

9 19 9 10 9 Fluorine

7 14 7 7 7 Nitrogen

20 20

13 27

56 26

Atomic Number

Mass Number

Number of Protons

Number of Neutrons

Number of Electrons

Element

9 19 9 10 9 Fluorine

7 14 7 7 7 Nitrogen

20 40 20 20 20 Calcium

13 27

56 26

Atomic Number

Mass Number

Number of Protons

Number of Neutrons

Number of Electrons

Element

9 19 9 10 9 Fluorine

7 14 7 7 7 Nitrogen

20 40 20 20 20 Calcium

13 27 13 14 13 Aluminum

56 26

Atomic Number

Mass Number

Number of Protons

Number of Neutrons

Number of Electrons

Element

9 19 9 10 9 Fluorine

7 14 7 7 7 Nitrogen

20 40 20 20 20 Calcium

13 27 13 14 13 Aluminum

26 56 26 30 26 Iron

Questions

• Distinguish between atomic mass and atomic number.

• Distinguish which particles can be used to identify an element.

• Determine which particles represent the mass of an atom.

Assignment

• Complete “Determining the Number of atomic particles” worksheet