Available Answers

1. 1.

   Name the following.

   1. An element having valencies 1,3,5 and 7.
   2. A polyatomic element.
   3. The symbol for iron with valency 3.
   4. An element having valencies 2 and 4.
   5. The element whose chemical symbol is Br
2. 2.

   Write T for true and F for False.

   1. A cation is a positively charged particle.
   2. Charged particles formed when an atom or a group of atoms gain or lose electrons are called atoms.
   3. A hydrogen atom loses an electron to form a cation, which is represented as H⁺².
   4. Fluorine gains an electron and forms anion (fluoride ion) with symbol F^2-.
   5. 3O₂ mean two molecules of ozone.
3. 3.

   Write T for True and F for False.

   1. The valency of an element is the same as its atomicity.
   2. Valencies help in deriving a chemical symbol.
   3. Modern periodic table has 18 horizontal rows and 7 vertical columns.
   4. The formula for sulphuric acid is H₂SO₄.
   5. In a periodic table, the elements with similar chemical properties appear in vertical columns.
4. 4.

   Name the following.

   1. The polyatomic ion with charge.
   2. An element of group 17 of the periodic table.
   3. A member of period 3 of the periodic table.
   4. The smallest particle of a compound that can exist independently.
   5. A group of atoms that functions as a single unit.
5. 5.

   Choose the correct option.

   1. Which one of the following is an example of triatomic molecule/
      1. CO
      2. S₂
      3. CO₂
      4. HCl
   2. Which one of the following is an example of a molecule?
      1. OH-
      2. O
      3. O₂
      4. H+
   3. Identify the cation
      1. H₃O+
      2. CO
      3. H₂O
      4. F-
   4. Which polyatomic ion does NaNO₃ contain?
      1. Carbonate
      2. Nitrite
      3. Sodium
      4. Nitrate
   5. Which one of the following cannot exist independently?
      1. He
      2. H₂SO₄
      3. H₂
      4. SO₄^2-
6. 6.

   Write T for True and F for False. Correct the false statement (s).

   1. An atom or group of atoms that gains electron(s) and develops a negative charge is called cation.
   2. Oxide anion bears 2 unit charge.
   3. Sodium hydroxide is a compound in which sodium bears positive charge and hydroxide bears negative charge.
   4. Molecules of chloride and oxygen ae diatomic.
   5. Iron with a valency of 2 is written as Fe(2).