1.2 c: Atomic mass and number

Atomic Number and Atomic Mass

​Syllabus dot points

• 1.2 c calculate the relative atomic mass from isotopic composition (ACSCH024)

​What we will learn

• Atomic structure review

• Periodic Table review

• Atomic number

• Atomic mass

• Calculating subatomic particles

Multiple Choice

Structure B is

• The nucleus

• An electron shell

• An energy level

Multiple Choice

Structure C is a(n)

• Proton

• Neutron

• Electron

Multiple Choice

Structure D is a(n)

• Proton

• Neutron

• Electron

Multiple Choice

Structure E is a(n)

• Proton

• Neutron

• Electron

​The Periodic Table:

• Atomic number

• Atomic mass

• Symbol

• Name

Drag and Drop

Rows in the periodic table are called

Placeholder

Columns in the periodic table are called ​

Placeholder

Drag these tiles and drop them in the correct blank above

period

group

Multiple Choice

Elements in the periodic table are sorted by:

• Increasing atomic number

• Increasing atomic mass

• Alphabetical order

• Increasing number of valence electrons

Fill in the Blanks

Write the symbol of the element Oxygen.

Fill in the Blanks

Write the symbol of the element Nitrogen.

Fill in the Blanks

Write the symbol of the element Sodium.

​Atomic number

• The main identifying number of an element

• Equal to the number of protons in the atom

• In a neutral atom, it is also equal to the number of electrons

​Atomic mass

• A trickier concept

• The average of all isotopes masses of an element

• Isotope = a form of an element's atom that has the same number of protons, but a different number of neutrons. Therefore, a different mass.

Extension: Calculating atomic mass

​Calculating subatomic particles

• Protons is easy! = the atomic number

• Electrons is also easy (for neutral atoms!) = the number of protons = the atomic number

• Neutrons is trickier...

​Calculating neutrons

• The mass of an atom is in its nucleus

• The nucleus is made up of the neutrons + protons

• If we know the number of protons, we can....

Protons + neutrons = mass number

Therefore:

Mass number - atomic number = number of neutrons

​Bohr Diagrams:

• Used to display the number of subatomic particles and especially the position of electrons in an atom

• 1st shell = 2 electrons

• 2nd shell = 8 electrons

• 3rd shell = 8 electrons (16 electrons)

Multiple Choice

Sodium has an atomic number of 11, how many protons does this atom have?

• 22

• 11

• 12

• 2

Multiple Choice

How many neutrons are in Magnesium?

• 36

• 12

• 24

• 6

Multiple Choice

How many electrons are in Aluminium?

• 40

• 27

• 13

• 14

Multiple Choice

How many protons are in Silicon?

• 7

• 42

• 28

• 14

Multiple Choice

How many neutrons are in Phosphorus?

• 16

• 15

• 31

• 46

Multiple Choice

How many electrons are in Sulfur?

• 32

• 16

• 48

• 8

Multiple Choice

How many neutrons are in Argon?

• 18

• 40

• 58

• 22

​Up next:

Electrons around the nucleus

Historical atomic structure

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