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

​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

​Re

Re

​Re

Re

​Re

Re