Available Answers

1. 1.

   State whether the following statements are true or false. If false, write the correct statement.

   1. A symbol is the short form or abbreviated name of an element.
   2. Symbol 'O' represents one molecule of the element - oxygen.
   3. A symbol represents - the weight of the element equal to its molecular weight.
   4. The symbol 'Zn' distinguishes element -  Zn from other elements.
   5. The symbol 'C' - the first letter of the element carbon is not approved as a symbol since calcium & copper also begin with 'C',
   6. The symbol 'Mg' for magnesium was derived from its Latin name - 'Magnesia'.
   7. An element named from the first two letters of the name of the element - was an inert gas - the second element of the modern periodic table.
   8. The symbol for bromine is 'Br' & of bromide is 'Br₂'.
   9. The element boron - a metalloid has the symbol 'Be'.
2. 2.

   Complete the statements by selecting the correct word/s from the choice 'A', 'B' or 'C'.

   1. Valency is the number of 'X' atoms which can combine with or displace one atom of the element or radical forming a compound.
      1. 'X' = oxygen
      2. 'X' = hydrogen
      3. 'X' = nitrogen
   2. In the compound ammonia - 'NH₃' - three atoms of hydrogen, combine with one atom of nitrogen. The valency of nitrogen is -
      1. One
      2. Three
      3. Two
   3. Magnesium combines with oxygen to give magnesium oxide (MgO). The valency of oxygen is two, so the valency of magnesium is -
      1. One
      2. Two
      3. Three
   4. The valency of sodium in sodium sulphite is
      1. One
      2. Two
      3. Three
   5. The valency of copper in the compound 'Cu₂O' is
      1. Two
      2. One
      3. Three
   6. The valency of iron in the compound 'Fe₂S₃' is
      1. One
      2. Two
      3. Three
   7. Lead exhibits variable valency of
      1. Two & four
      2. One & four
      3. Three & four
   8. The valency of nitrogen in magnesium nitride - 'Mg₃N₂' is
      1. One
      2. Two
      3. Three
   9. Calcium [2, 8, 8, 2] donates two electrons to form a cation. It's valency is
      1. 2^-
      2. 2⁺
      3. 1¹⁺
   10. Copper & silver exhibit - variable valency of
       1. 1¹⁺ & 2⁺
       2. 1^- & 2^-
       3. 2⁺ & 1^-
3. 3.

   Complete the table given below by filling in the blanks with the
   a) correct symbols
   b) valency of the elements & radicals

   Element/Radical	Symbol	ion
   Potassium	K	K1+
   Sodium
   Hydrogen
   Ammonium
   Calcium
   Magnesium
   Zinc
   Barium
   Nickel
   Aluminium
   Chromium

    

   Element/Radical	Symbol	ion
   Chlorine	Cl	Cl1-
   Bromine
   Iodine
   Nitrate
   Hydroxide
   Bicarbonate
   Bisulphite
   Bisulphate
   Aluminate
   Permanganate
   Oxygen
   Sulphur
   Sulphite
   Sulphate
   Carbonate
   Dichromate
   Zincate
   Plumbite
   Phosphate
   Nitrogen

    

   Variable Valency

   	1+	2+	3+	4+
   Copper
   Silver
   Mercury	Hg	Hg
   Iron
   Tin		Sn		Sn
   Lead

4. 4.

   Complete the table given below of the -
   a) symbols
   b) electronic configuration
   c) valency of the first 20 elements

   

5. 5.

   Complete the table given below pertaining to a step by step simple method for writing a formula - of a chemical compound.

   

6. 6.

   Fill in the blanks - with the correct formula for the given compounds - or with the names of the compounds whose formulas are given.