SPM Chemistry (KSSM) Paper 1

01 Introduction to Chemistry
1.1 Chemistry and Its Importance
1 Lesson
1.1.1 Chemistry and Its Importance
1.2 Scientific Investigation
1 Lesson
1.2.1 Scientific Investigation
02 The Structure of Atoms
2.1 The Basic Concept of Matter
2 Lessons
2.1.1 The Particle Theory of Matter
2.1.2 The Three States of Matter
2.2 The History of Development of the Atomic Model
1 Lesson
2.2.1 The History of Development of the Atomic Model
2.3 The Structure of Atom
2 Lessons
2.3.1 The Structure of Atom
2.3.2 Electrons Arrangement in Atom
2.4 Isotopes and Their Uses
1 Lesson
2.4.1 Isotopes and Their Uses
2.5 The Structure of Atom – Practices
03 Concept of Mole, Formulae and Equations
3.1 Relative Atomic Mass and Relative Molecular Mass
1 Lesson
3.1.1 Relative Atomic Mass and Relative Molecular Mass
3.2 Concept of Mole
3 Lessons
3.2.1 Concept of Mole
3.2.2 Number of Mole and Mass
3.2.3 Number of Mole and Volume of Gases
3.3 Chemical Formulae
2 Lessons
3.3.1 Chemical Formulae
3.3.2 Formula of Ionic Compounds and Molecule
3.4 Chemical Equations
1 Lesson
3.4.1 Chemical Equations
3.5 Chemical Formulae and Equations – Practices (Coming Soon)
04 Periodic Table of Elements
4.1 The Development of Periodic Table
1 Lesson
4.1.1 Development of Periodic Table
4.2 Arrangement of Element in Periodic Table
1 Lesson
4.2.1 Arrangement of Electrons in Periodic Table
4.3 Group 18 Elements
1 Lesson
4.3.1 Group 18 Elements
4.4 Group 1 Elements
2 Lessons
4.4.1 Group 1 Elements
4.4.2 Chemical Properties of Group 1 Elements
4.5 Group 17 Elements
2 Lessons
4.5.1 Group 17 Elements
4.5.2 Chemical Properties of Group 17 Elements
4.6 Elements in Period 3
1 Lesson
4.6.1 Elements in Period 3
4.7 Transition Elements
1 Lesson
4.7.1 The Transition Elements
4.8 Periodic Table – Practices (Coming Soon)
1 of 3
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2.3.1 The Structure of Atom

SPM Chemistry (KSSM) Paper 1 2.3 The Structure of Atom 2.3.1 The Structure of Atom

The Modern Atomic Model

According to the modern atomic model,
  1. The central nucleus consists of protons and neutrons. It containing almost all the mass of the atom.
  2. the nucleus of an atom is very small compared to the size of the atom
  3. the electrons are orbiting outside the nucleus in the electron shells
  4. the electrons are moving in electron shells at a very high speed and we cannot determine the position of the electrons at a particular time
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The Subatomic Particles of an Atom​

  1. Atoms are made up of tiny particles called subatomic particles.
  2. An atom contains three types of subatomic particles:
    1. proton,
    2. neutron and
    3. electron,
  3. The proton and neutron form the nucleus at the centre of an atom. They are also called the nucleon of an atom.
  4. The electron moves around the nucleus at a very high speed.
  5. The nucleus is positively charged because of the presence of protons, which are positively charged. The neutrons are neutral.
  6. The symbols, charge and relative masses of proton, neutron and electron are as below.
ParticleSymbolRelative chargeRelative mass
Proton
p
+1
1
Neutron
n
0
1
Electron
e
-1
1/1840
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The Charge of Particles

  1. A neutral atom contains the same number of electrons as the protons.
  2. The positive and negative charges of the protons and electrons respectively neutralise each other, for example, (+4) + (-4) = 0
  3. If the number of protons is greater than the number of electrons, the particle is positively charged.
  4. If the number of protons is greater than the number of electrons, the particle is positively charged.

Example:

Number of protonsNumber of electrons
Charge
3
3
0
5
2
+3
9
10
-1
11
10
+3
16
18
-2
17
18
-1
20
18
+3
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Proton Number and Nucleon Number

  1. Proton number = the number of protons
  2. Nucleon number = Number of protons + Number of neutrons

Proton Number

  1. The proton number (Z) represent the number of protons found in the nucleus of an atom.
  2. Proton number = the number of protons
  3. The proton number is also known as the atomic number.
  4. In an atom of neutral charge, the number of electrons also equals the atomic number.
  5. Hence, the proton number of an atom can also represent the number of electrons.

Nucleon Number

  1. The nucleon number (A), also called atomic mass number or mass number, is the number of protons plus the number of neutrons in an atomic nucleus. (Nucleon number = Number of protons + Number of neutrons)
  2. The nucleon number of an atom is about the same as the mass of the atom because the mass of an electron is very small and can be ignored.
Atom
Proton Number
Nucleon Number
Amount of Proton
Amount of Neutron
Helium
2
4
2
2
Oxygen
8
16
8
8
Sodium
11
23
11
12
Chlorine
17
35
17
18
[Notes: In ion, the amount of protons IS NOT equal to the amount of electrons]
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