Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
SMK SEKSYEN 10 KOTA DAMANSARA
47810 PETALING JAYA, SELANGOR
CHEMISTRY MODULE
(FIRST TERM, 2012)
TOPIC 1 :
ATOMS, MOLECULES AND
STOICHIOMETRY
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
CHECKLIST TO SCORE A IN CHEMISTRY
(Tick after tutorial /revision class)
Topic
1.1
Fundamental
particles of an
atom
Sub-topics
1. describe the properties of protons, neutrons, and electrons
in terms of their relative charges and relative masses
Tick
2. predict the behaviour of beams of protons,neutrons, and
electrons in both electric and magnetic fields
3. describe the distribution of mass and charges within an
atom
4. determine the numbers of protons, neutrons, and electrons
present in both neutral and charged species of a given
proton number and nucleon number
5. describe the contribution of protons and neutrons to
atomic nuclei in terms of proton and nucleon number
6. distinguish between isotopes based on the Number of
neutrons present; state examples of both stable and
unstable isotopes
1.2
Relative
atomic,
isotopic,
molecular &
formula
masses
1. define the terms relative atomic mass, Ar, relative isotopic
mass, relative molecular mass, Mr, and relative formula
mass based on 12C;
2. interprete mass spectra in terms of relative abundance of
isotopes and molecular fragments;
3. calculate relative atomic mass of an element from the
relative abundance of its isotopes or its mass spectrum.
1. define mole in terms of the Avogadro constant;
1.3
The mole and
the
Avogadro
constant
2. calculate the number of moles of reactants, volumes of
gases, volumes and concentrations of solutions;
3. deduce stoichiometric relationships from the calculations
above
**SEKIRANYA MASIH ADA SUB-TOPIC YANG TIDAK FAHAM,
SILA JUMPA GURU ANDA DENGAN SEGERA ATAU
MEMBUAT
ULANGKAJI
SERTA-MERTA.
PRACTICE MAKE PERFECT
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
Sub-topic 1.1 : Fundamental particles of an atom
Learning outcomes: Candidates should be able to:
(a) describe the properties of protons, neutrons and electrons in terms of their relative charges and relative masses;
(b) predict the behaviour of beams of protons, neutrons and electrons in both electric and magnetic fields;
(c) describe the distribution of mass and charges within an atom;
(d) determine the number of protons, neutrons and electrons present in both neutral and charged species of a given
proton number and nucleon number;
(e) describe the contribution of protons and neutrons to atomic nuclei in terms of proton number and nucleon
number;
(f) distinguish isotopes based on the number of neutrons present, and state examples of both stable and unstable
isotopes.
1. The properties of the subatomic particles of an atom:
Particle
Proton
Neutron
Electron
Symbol
Charge
Relative mass (a.m.u)
2. The effect of electric field on subatomic particles:
3. The effect of magnetic field on subatomic particles:
4. The distribution of mass and charges within an atom:
In this atomic model (James Chadwick):
(a) The nucleus of an atom consists of
___________ and ____________
occupying a small space in the centre of
the atom.
(b) Electrons are moving around the nucleus
in permissible orbits or electron shells
(also known as quantum shells).
This implies that a big section of an atom is made up of empty space. However, 99.98% of the mass of the
atom is concentrated in the nucleus.
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
5. Number of neutron in a nucleus = nucleon number – proton number
Element
Symbol
Number of protons
Number of nucleons
Number of electrons
No. of electrons
Aluminium
Aluminium
ion
Argon
Beryllium
Boron
Calcium
Carbon
Chlorine
Chloride ion
Fluorine
Fluoride ion
Helium
Hydrogen
Lithium
Lithium ion
Magnesium
Neon
Nitrogen
Oxygen
Phosphorus
Potassium
6. The contribution of protons and neutrons to atomic nuclei in terms of proton number and nucleon number
a) The ____________________is the number of protons in the nucleus of an atom. Atoms are neutral
particles. Hence, the number of protons in the nucleus of an atom is the same as the number of electrons
surrounding the nucleus.
b) The elements in the Modern Periodic Table are arranged in ascending order of proton numbers
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
7. Isotopes are atoms of the same element with the same __________ number but different ________ number.
a) The isotopes of an elementhave the same __________ properties because they have the same electron
arrangement but their __________ properties differ.
b) Stable isotopes : the nuclei of stable isotopes will not disintegrate spontaneously
c) Unstable isotopes = radioactive isotopes, which will disintegrate spontaneously by emitting alpha
particles (α particles, 42He2+), beta particles (β particles, 0-1e) and gamma-rays (γ rays) which are
electromagnetic waves with very short wavelength. This disintegration is known as radioactive decay.
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
Sub-topic 1.2 : Relative atomic,isotopic, molecular & formula masses
Learning outcomes: Candidates should be able to:
a) define the terms relative atomic mass, Ar, relative isotopic mass, relative molecular mass, Mr, and relative formula
mass based on 12C;
b) interprete mass spectra in terms of relative abundance of isotopes and molecular fragments;
c) calculate relative atomic mass of an element from the relative abundance of its isotopes or its mass spectrum.
1.
Relative atomic mass, Ar = the average mass of an atom of the element compared to 1/12 the mass of 12C
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
2.
Relative molecular mass, Mr = the ratio of the average mass of 1 molecule of a substance to 1/12 the
mass of 12C
3.
Relative isotopic mass = the ratio of the mass of an atom of the isotope to 1/12 the mass of 12C
Formula:
4.
Relative formula mass = the ratio of the average mass of 1 molecule of ionic compound to 1/12 the mass of 12C
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
5. Mass Spectrometry
a) Is used to determine the
i.
Relative isotopic mass
ii.
Relative abundance of an isotopes in a sample of the element
iii.
Relative atomic mass
iv.
Relative molecular mass
v.
Structure of organic compounds
b) Apparatus used : mass spectrometer
c) Ar = ah1 + bh2
h1+h2
Relative abundance
h1
h2
a
b
m/e
d) relative abundance/isotopic abundance = the abundance of each isotope in the mixture. It can
be express in terms of fractional abundance or percentage abundance.
e) The mass spectrum of methane :
The CH4+ is called the molecular ion (M) or the parent ion and appear at the m/e value of 16,
corresponding to the Mr of methane. Naturally occurring carbon is made up of 99% of 12C
isotope and 1% 13C isotope (peak M+1). The peak M+1 can be ignored in the determining of the
Mr of the compound.
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Topic 1: Atoms, Molecules and Stoichiometry
f)
First Term (2012)
The mass spectrum of ethanol :
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Topic 1: Atoms, Molecules and Stoichiometry
First Term (2012)
Sub-topic 1.2 : Relative atomic,isotopic, molecular & formula masses
Learning outcomes: Candidates should be able to:
a) define mole in terms of the Avogadro constant;
b) calculate the number of moles of reactants, volumes of gases, volumes and concentrations of solutions;
c) deduce stoichiometric relationships from the calculations above.
1.
One mole is defined as the quantity of a substance that contains the same number of particles ( atoms, ions,
or molecules) as there are atoms in exactly 12g of 12C. The number of atoms present in 1 mol of 12C is called
the Avogadro constant and is equivalent to 6.02 X 1023.
Source :
1.
2.
3.
4.
,Ace Ahead Chemistry Volume 1, Oxford Fajar
Chemistry for SPM, Cengage Learning
Pre-U Text STPM Physical Chemistry, Longman
Success Chemistry SPM, Oxford Fajar
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