The mass of atoms. Objectives Today we will learn: What atomic number and mass number mean The...
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Transcript of The mass of atoms. Objectives Today we will learn: What atomic number and mass number mean The...
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
• 12g of C
• 197g of Au
• 7g of Li• 88g of Sr
• 56g of Fe
• 119g of Sn
• 48g of Ti
• 23g of Na
• 24g of Mg• 91g of Zr• 40g of Ca
• 84g of Kr• 11g of B
• 127g of I
• 80g of Br
• 1g of H
• 75g of As
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
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 HaikuConvert mass to moleThen divide it by the smallMultiply til whole
Example
Na S O
Percentage 29.1% 40.5% 30.4%
Convert Mass to
Mole
29.1 / 23 =
1.265217
40.5 / 32
1.265625
30.4 / 16
1.9
Then divide it by the
small
1.2652171.265217
=1
1.2656251.265217
=1
1.91.265217
=1.5
Multiply til whole
X 22 2 3
Convert mass to moleThen divide it by the smallMultiply 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.