1.1. Answers

Section A: Multiple Choice Questions (8 Questions)

1. Which subatomic particle has a positive charge?
   a) Proton    b) Electron    c) Neutron    d) Nucleus

2. Which element has the electronic configuration 2,8,3?
   a) Aluminium    b) Magnesium    c) Sodium    d) Chlorine

3. Which subatomic particle has almost no mass?
   a) Proton    b) Neutron    c) Electron    d) Nucleus

4. Which statement about Dalton’s Atomic Theory is correct?
   a) Atoms can be divided into smaller particles
   b) Atoms of the same element are identical
   c) Atoms of the same element have different masses
   d) Atoms are created in chemical reactions

5. Which is NOT a property of ionic compounds?
   a) High melting points
   b) Conduct electricity when molten
   c) Soft and easily melted
   d) Form crystals

6. Which is the correct symbol for an ion with 17 protons and 18 electrons?
   a) Cl⁺    b) Cl⁻    c) Cl²⁻    d) Cl²⁺

7. Which shell can hold a maximum of 8 electrons?
   a) 1st    b) 2nd    c) 3rd    d) All of these

8. What holds the ions together in an ionic bond?
   a) Sharing of electrons
   b) Electrostatic attraction
   c) Covalent forces
   d) Magnetic attraction

 

 

 

 

Section B: Fill in the Blanks (5 Questions)

9. Atoms are made of protons, NEUTRONS, and electrons.

10. A positive ion is called a CATION.

11. The number of protons in an atom is its ATOMIC number.

12. Sodium and chlorine form IONIC bonds when they react.

13. Ionic compounds form a LATTICE structure.

Section C: Short Answer Questions (8 Questions)

14. Define atomic number and mass number.

• Atomic number, Z → number of protons
• Mass number, A → number of protons + nuetrons

15. Explain why atoms are electrically neutral.

• charge on electrons (negative) and protons (positive) balance.

16. State the relative charges and masses of protons, neutrons, and electrons.

	proton (p)	neutron (n )	electron (e)
mass	1	1	∼0
charge	+1	0	-1

17. Explain why ionic compounds have high melting points.

Ionic compounds have high melting points because the ions in their structure are held together by strong electrostatic forces.

Each positive ion (cation) and negative ion (anion) is arranged in a giant lattice structure, where every ion is strongly attracted to many oppositely charged ions around it. These attractions are called ionic bonds, and they are very strong.

To melt an ionic compound, you need to supply enough energy to overcome all of those strong attractions throughout the entire lattice. This requires a large amount of heat energy, which is why ionic compounds like sodium chloride have very high melting points.

18. Define cation and anion with examples.

• Cation → positively charged ion: Na⁺  
• Anion → negatively charged ion: Cl^-

19. Describe the difference between an element, a compound, and a mixture. 

• element is a specific atom
• compound is two or more different elements bonding together
• mixture is the combination of two or more compounds and/or elements

20. Write the electronic configuration of sulfur (atomic number 16).

• 2, 8, 6

21. What information does the group and period number of an element give?

• Group number (vertical column in the periodic table):
  The group tells you how many electrons are in the outermost shell (valence electrons) of the atom.
  Example: Sodium (Na) is in Group 1, meaning it has 1 electron in its outer shell. Chlorine (Cl) is in Group 17, meaning it has 7 outer electrons.

• Period number (horizontal row):
  The period tells you how many electron shells (energy levels) the atom has.
  Example: Sodium (Na) is in Period 3, so it has 3 electron shells. Oxygen (O) is in Period 2, so it has 2 shells.

Section D: Diagram Questions (4 Questions)

22. Draw and label the structure of an atom of carbon.

23. Show the dot-and-cross diagram for NaCl.

24. Indicate the number of protons, neutrons, and electrons in an aluminum atom (₁₃²⁷Al).

• Z = 13
• N = A - Z = 27 - 13 = 14
• e = 13

25. Draw the arrangement of electrons in a magnesium atom.

Section E: Application Questions (5 Questions)

26. Explain why ionic compounds do not conduct electricity when solid but do when molten or dissolved.

27. Magnesium forms Mg²⁺ ions while sodium forms Na⁺ ions. Which compound would have a higher melting point: MgO or NaCl? Explain why.

28. Why is it important for atoms to achieve a full outer shell of electrons?

29. Predict the formula of the compound formed between aluminium and oxygen. Explain your reasoning.

30. Explain why aluminium oxide has a higher melting point than sodium chloride.