CHEMISTRY FORM 2
- 1.1 Structure of the atom
- 1.2 Atomic Number and Mass Number
- 1.3 Isotopes
- 1.4 Energy levels and electron arrangement
- 1.5 Development of the Periodic Table
- 1.6 Relative Atomic Mass and Isotopes
- 1.7 Ion Formation
- 1.8 Chemical Formulae
- 1.9 Chemical Equations
- 2.1 Alkali metals (Group I elements)
- 2.2 Alkali Earth Metals (Group II elements)
- 2.3 Halogens (Group VII elements)
- 2.4 Noble gases (Group VIII elements)
- 2.5 Properties and Trends Across the Periodic Table
- 3.1 Bond
- 3.2 Ionic bond
- 3.3 Giant ionic structure
- 3.4 Covalent bond
- 3.5 Co-ordinate bond
- 3.6 Molecular structures
- 3.7 Giant covalent structures
- 3.8 Metallic Bond
- 3.9 Types of bond across a period
- 3.10 Oxides of elements in Period 3
- 3.11 Chlorides of Period 3 elements
- 4.1 What is a salt?
- 4.2 Types of salt
- 4.3 Solubility of salts in water
- 4.4 Methods of preparing salts
- 4.4.1 Reacting a Metal with an Acid
- 4.4.2 Reacting an Acid with a Base (Neutralization)
- 4.4.3 Reacting an Acid with a Carbonate (or hydrogencarbonate of metal)
- 4.4.4 Combining elements Directly (Direct Combination of elements)
- 4.4.5 Precipitation (Double decomposition)
- 4.5 Action of heat on salts
- 4.6 Uses of salts
- 5.1 Electrical conduction
- 5.2 Electrical conductivity of molten substances
- 5.3 Electrical conductivity of substances in aqueous state
- 5.4 Electrolysis
- 5.5 Applications of electrolysis
- 6.1 Allotropes of carbon
- 6.2 Chemical properties of carbon
- 6.3 Carbon (IV) oxide
- 6.4 Carbon (II) oxide (CO)
- 6.5 Large scale production of sodium carbonate and sodium hydrogencarbonate
- 6.6 Effect of carbon (II) oxide and carbon (IV) oxide on the environment
- 6.7 Carbon cycle
Structure of the Atom, and the Periodic Table: Isotopes
1.0 Structure of the Atom, and the Periodic Table
1.3 Isotopes
Study the atoms represented in Figure 1.3.1, looking for the similarities and differences between them.
Figure 1.3.1: Isotopes
Questions 1.3(b) 
- State two similarities between the atoms A, D and E.
- Identify two ways in which all the three atoms are different.
- What is the evidence that these atoms represent the same element?
- Which element do these atoms represent? Explain your answer.
- Which of the atoms A, D and E is the lightest, and which one is the heaviest?
Hint: Refer to Table 1.2.3
Answers to Questions 1.3(b)
Atoms A, D, and E are isotopes. Isotopes are atoms of the same element, with the same number of protons, but different numbers of neutrons (or mass numbers). In Table 1.2.3, helium and carbon are other examples of elements with isotopes.
We differentiate isotopes by indicating their mass numbers. For example, a hydrogen atom with no neutron is hydrogen-1, with one neutron is hydrogen-2, and with two neutrons is hydrogen-3. Similarly, helium can be helium-4 or helium-3, while carbon can be carbon-12 or carbon-14 and so on. Isotopes are represented in the form shown in Figure 1.3.2.
Figure 1.3.2: Representation of isotope
Chlorine-35 and chlorine-37 isotopes, for example, are represented as shown in Figure 1.3.3.
Figure 1.3.3: Chlorine isotopes