10th Science Book Back Answers Unit 8 – Periodic Classification Of Elements:
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Samacheer Kalvi 10th Science Book Back Answers Chemistry Unit 8 – Periodic Classification Of Elements:
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10th Science – Chemistry
Unit 8: Periodic Classification Of Elements
I. Choose the best answer:
1. The number of periods and groups in the periodic table is.
a) 6,16 b) 7,17 c) 8,18 d) 7,18
Ans : (d) 7,18
2. The basis of modern periodic law is.
a) atomic number b) atomic mass c) isotopic mass d) number of neutrons
Ans : (a) atomic number
3. group contains the member of halogen family.
a) 17th b) 15th c) 18th d) 16th
Ans : (a) 17th
4. is a relative periodic property.
a) Atomic radii b) Ionic radii c) Electron affinity d) Electronegativity
Ans : (d) Electronegativity
5. Chemical formula of rust is .
a) FeO.xH2O b) FeO4.xH2O c) Fe2O3.xH2O d) FeO
Ans : (c) Fe2O3.xH2O
6. In the alumino thermic process the role of Al is.
a) oxidising agent b) reducing agent c) hydrogenating agent d) sulphurising agent
Ans : (b) reducing agent
7. The process of coating the surface of the metal with a thin layer of zinc is called.
a) painting b) thinning c) galvanization d) electroplating
Ans : (c) galvanization
II. Fill in the blanks
1. If the electronegativity difference between two bonded atoms in a molecule is greater than 1.7, the nature of bonding is. Ans : Ionic
2. is the longest period in the periodical table. Ans: 6, 7
3. forms the basis of the modern periodic table. Ans: Atomic Number
4. If the distance between two Cl atoms in the Cl2 molecule is 1.98Å, then the radius of the Cl atom is.
Ans: 0.99 A
5. Among the given species A–, A+, and A, the smallest one in size is. Ans: A+
6. The scientist who propounded the modern periodic law is. Ans: Henry Moseley
7. Across the period, ionic radii (increases, decreases). Ans: decreases
8. _______ and ______ are called inner transition elements. Ans: Lanthanides and Actinides.
9. The chief ore of Aluminium is ______. Ans: Bauxite (Al2O3.2H2O).
10. The chemical name of rust is ______.
Ans: Hydrated ferric oxide.
III. Match the following:
1. Galvanisation – (a) Noble gas elements
2. Calcination – (b) Coating with Zn
3. Redox reaction – (c) Silver–tin amalgam
4. Dental filling – (d) Alumino thermic process
5. Group 18 elements – (e) Heating in the absence of air
Answer:
1 – (b), 2 – (e), 3 – (d), 4 – (c), 5 – (a).
III. True or False (Correct the Statement if it is false)
1. Moseley’s periodic table is based on atomic mass.
Ans: False. Mosley’s periodic table is based on atomic numbers.
2. Ionic radius increases across the period from left to right.
Ans: False. Ionic radius decreases across the period from left to right.
3. All ores are minerals, but all minerals cannot be called as ores;
Ans: True.
4. Al wires are used as electric cables due to their silvery white colour.
Ans: False. Aluminum wires are used as electric cables due to their good conductor of heat and electricity.
5. An alloy is a heterogeneous mixture of metals.
Ans: False. An alloy is a homo
V. Assertion and Reason
Answer the following questions using the data given below:
a) A and R are correct, R explains the A.
b) A is correct, R is wrong.
c) A is wrong, R is correct.
d) A and R are correct, R doesn’t explains A.
1. Assertion: The nature of bond in HF molecule is ionic.
Reason: The electronegativity difference between H and F is 1.9.
Ans : (a) A and R are correct, R explains the A
2. Assertion: Magnesium is used to protect steel from rusting.
Reason: Magnesium is more reactive than iron.
Ans : (c) A is wrong, R is correct
3. Assertion: An uncleaned copper vessel is covered with greenish layer.
Reason: Copper is not attacked by alkali.
Ans : (a) A and R are correct, R explains the A
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