078 145 46 78
Marks
Garde 8
Chemistry 2025/26
Name: …………………………………………………………
Date: …………………………………………………………..
1. Chose the correct answer.
1.
The atomic number of an element tells you its number of
1.
Neutrons
2. Protons
3. electrons plus protons
4. nucleons
2. In Bohr’s model, electrons occupy concentric circles called
1.
Orbitals
2. Shells
3. Lattices
4.layers
3. Which group in the Periodic Table contains the noble gases?
1.
Group 1
2. Group 7
3. Group 8
4. Group 0
4. An ionic bond forms when atoms
1.
share electrons
2. transfer electrons
3. share protons
4. transfer neutrons
5. A covalent bond is correctly represented by
1.
Na⁺ and Cl⁻
2. electron shells
3. shared electron pairs
4.lattice of ions
6. Which allotrope of carbon has a giant three-dimensional lattice?
1.
Graphite
2. Diamond
3. Fullerene
4. Carbon dioxide
7. Dot and cross diagrams are used to show
1.
ionic lattices
2. proton arrangement
3. electronic structure of bonds
2. concentric shells
8. The outermost electron shell determines
1.
atomic number
2. mass number
3. chemical reactivity
4. density
9. Intermolecular forces are weakest in
1.
Solids 2. Liquids
3.gases
4. lattices
10. Kinetic particle theory explains that in a gas, particles
1.
vibrate in place
2. slide over one another
3. move randomly at high speed
4. form a fixed lattice
2. Write Short Answer for the following questions.
1.
Define mass number.
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2. What is an ion?
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3. State the general trend of atomic radius across a period.
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4. Explain the role of electrostatic forces in ionic bonding.
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5. Give the electronic configuration of chlorine (atomic number 17).
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6. List two properties of alkali metals.
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7. What makes a molecule stable?
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8. Define a giant covalent structure.
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9. Name three factors that affect the rate of evaporation.
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10. Briefly describe the kinetic particle theory for liquids.
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3. Answer the following questions.
1.
Explain how to calculate the number of neutrons in an atom given its atomic and mass numbers.
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2. Describe the arrangement of particles in graphite and explain why it conducts electricity.
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3. Draw a dot and cross diagram for sodium chloride and label its ions.
4. Draw a dot and cross diagram for a water molecule, showing all electron pairs.
5. Discuss how the Periodic Table is organized in terms of energy levels and group properties.
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6. Explain why halogens become less reactive down the group, referring to outermost electron shells.
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4. Match each term in Column A with the correct description in Column B.
Column A
Column B
A. atomic number
1. atoms share electrons
B. concentric shells
2. charged atom
C. noble gases
3. number of protons
D. covalent bond
4. particle arrangement in gases
E. ion
5. group with very low reactivity
F. lattice
6. three-dimensional array of particles
G. intermolecular forces
7. forces between molecules
H. alkali metals
8. group 1 elements
I. outermost electron shell
9. highest occupied energy level
J. mass number
10. protons + neutrons
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5. True (T) or False (F) Questions
1.
The mass number equals the sum of protons and electrons.
2. Alkali metals are found in Group 1 of the Periodic Table.
3. Noble gases readily form ionic bonds.
4. Covalent compounds generally have high melting points.
5. In a lattice, electrostatic forces act between oppositely charged ions.
6. Diamond has layers that slide over each other easily.
7. Graphite conducts electricity because of delocalized electrons.
8. The kinetic particle theory states that particles in a solid move freely.
9. Ionic compounds conduct electricity when molten or dissolved.
10. Halogens have seven electrons in their outermost shell.
6. Calculation Questions
1.
An atom has atomic number 11 and mass number 23. Calculate its number of protons, neutrons, and
electrons.
2. Chlorine has two main isotopes: Cl-35 (75%) and Cl-37 (25%). Calculate its relative atomic mass.
3. A sample of aluminum has mass 54 g and volume 20 cm³. Calculate its density in g/cm³.
4. Given magnesium’s atomic number 12, write its electronic structure using shell notation.(K,L,M,N)
5. How many electrons are in the outermost shell of sulfur (atomic number 16)?
6. Neon has atomic number 10. Write its dot and cross for the outer shell only.
7. Calculate the mass of one mole of sodium chloride (Na = 23, Cl = 35.5).
8. A piece of diamond of volume 2.5 cm³ has mass 8.75 g. Calculate its density.
9. An ionic lattice of calcium fluoride (CaF₂) contains 1×10²³ formula units. How many fluoride ions are
present?
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