The mass of atoms
Objectives
• Today we will learn:
• What atomic number and mass number mean
• The relative masses of subatomic particles
• What isotopes are
• That masses of atoms can be compared by their relative atomic masses
• That carbon 12 is used as a standard to measure relative atomic mass from
• That the relative masses of compounds can be calculated
True or False
• Atoms are charged particles
• Atoms contain charged particles
• Electrons are found in energy levels or shells
• Electrons have a negative charge
• Protons are found in the nucleus of an atom
• Neutrons are found in shells around the outside of an atom
What do you know about the atom…
Find the number of Protons, Electrons and
Neutrons and the mass number of the following…
• Li
• Na
• Al
•C
• Ar
• Ca
• Au
•N
•W
• Bi
• Hg4+
• F• Tc3+
What about chlorine?
Isotope
• Same number of protons different number of neutrons
Find the link between these
• 80g of Br
• 12g of C
• 56g of Fe
• 7g of Li
• 75g of As
• 127g of I
• 48g of Ti
• 88g of Sr
• 40g of Ca
• 91g of Zr
• 197g of Au
• 11g of B
• 24g of Mg
• 23g of Na
• 84g of Kr
• 119g of Sn
• 1g of H
The Mole
• Is based on Avogardos number
• 6.022 x 1023 particles in one
mole
Find the relative mass of the following…
• Li
• Na
• CO2
• Al2O3
• CH4
• Ar
• CaCO3
• Au
• N2
•W
• Bi
• H2O
• CuSO4•5H2O
Working out the number of moles
• 12g carbon
• 16g oxygen gas
• 9g gold
• 45g hydrogen
• 10g argon
Mass
No Moles
Relative Mass
Objectives
• Today we will learn:
•
•
•
•
•
•
What atomic number and mass number mean
The relative masses of subatomic particles
What isotopes are
That masses of atoms can be compared by their relative atomic masses
That carbon 12 is used as a standard to measure relative atomic mass from
That the relative masses of compounds can be calculated
• You can now
• Define atomic number and mass number
• Use the periodic table to get atomic & mass number to work out the number of each
subatomic particle that an atom has
• Give a definition of atomic mass
• Calculate relative formula masses
• State what a mole is
Calculations with Percentages, Formulae &
Equations
• You will learn…
• How to calculate the percentage of an
element in a compound from its
formula
• How to calculate the empirical
formulae of a compound from its
percentage composition
• That balanced symbol equations
show the relative numbers of
molecules of reactants and products
in a reaction
• That balanced symbols equations can
be used to calculate the masses of
reactants and products
• Teaser…
• How could you work out the % of
carbon in
CaCO3
Define
• Click here
Percentage of an element in a compound
• By Mass!
• Find the relative mass of the
compound
• Divide the total relative mass of
the element of interest by the
relative mass of the compound.
Mass of element of interest
Total Relative mass of substance
Percentage of an element in a compound
• For example…
• Find the percentage of oxygen in
magnesium oxide
• Magnesium oxide = MgO
• Mg = 24
• O = 16
• MgO = 40
• 16/40 = 40%
Mass of element of interest
Total Relative mass of substance
Questions
Empirical Formulae
• Empirical formula Haiku
Convert mass to mole
Then divide it by the small
Multiply til whole
Example
Na
S
O
Percentage
29.1%
40.5%
30.4%
Convert
Mass to
Mole
29.1 / 23 =
40.5 / 32
30.4 / 16
1.265217
1.265625
1.9
Then divide
it by the
small
1.265217
1.265217
=
1
1.265625
1.265217
=
1
1.9
1.265217
=
1.5
Multiply til
whole
X2
2
2
3
Convert mass to mole
Then divide it by the small
Multiply til whole
Questions
Calculations with Percentages, Formulae &
Equations
• You will learn…
• How to calculate the percentage of an
element in a compound from its
formula
• How to calculate the empirical
formulae of a compound from its
percentage composition
• That balanced symbol equations
show the relative numbers of
molecules of reactants and products
in a reaction
• That balanced symbols equations can
be used to calculate the masses of
reactants and products
• You have learnt…
• To calculate the percentage
composition of an element in a
compound
• To calculate the empirical formulae of
compounds from percentage
composition.