topic 1: atoms, molecules and...

Topic 1: Atoms, Molecules and Stoichiometry First Term (2012)

SMK SEKSYEN 10 KOTA DAMANSARA47810 PETALING JAYA, SELANGOR

CHEMISTRY MODULE (FIRST TERM, 2012)

TOPIC 1 : ATOMS, MOLECULES AND

STOICHIOMETRY


CHECKLIST TO SCORE A IN CHEMISTRY

(Tick after tutorial /revision class)

Topic Sub-topics Tick

1.1 Fundamental

1. describe the properties of protons, neutrons, and electrons in terms of their relative charges and relative masses

particles of an atom

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,

1. define the terms relative atomic mass, Ar, relative isotopic mass, relative molecular mass, Mr, and relative formula mass based on 12C;

molecular &formula masses

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.

1.3 1. define mole in terms of the Avogadro constant;

The mole and theAvogadro

2. calculate the number of moles of reactants, volumes of gases, volumes and concentrations of solutions;

constant 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


Sub-topic 1.1 : Fundamental particles of an atomLearning 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:

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).

Particle Symbol Charge Relative mass (a.m.u)Proton

NeutronElectron


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.

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 numbers7. 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, 4

2He2+), 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.


Sub-topic 1.2 : Relative atomic,isotopic, molecular & formula massesLearning 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


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


5. Mass Spectrometrya) Is used to determine the

i. Relative isotopic massii. Relative abundance of an isotopes in a sample of the elementiii. Relative atomic massiv. Relative molecular massv. 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.

f) The mass spectrum of ethanol :


Sub-topic 1.2 : Relative atomic,isotopic, molecular & formula massesLearning 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. ,Ace Ahead Chemistry Volume 1, Oxford Fajar2. Chemistry for SPM, Cengage Learning3. Pre-U Text STPM Physical Chemistry, Longman4. Success Chemistry SPM, Oxford Fajar

topic 1: atoms, molecules and...

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