Question

EXCERCISE 1(A)
1. What is a symbol ? What information does it convey ?
2. Why is the symbol S for sulphur, but Na for sodium and Si
for silicon ?
3. Write the full form of IUPAC. Name the elements
represented by the following symbols :
Au, Pb, Sn, Hg.
4. If the symbol for Cobalt, Co, were written as CO, what
would be wrong with it?
5. What do the following symbols stand for?
(a) H (b) H (c) 2H (d) 2H,
6. What is meant by atomicity ? Name a diatomic element.
7. (a) Explain the terms 'valency' and 'variable valency'.
(b) How are the elements with variable valency named ?
Explain with an example.
8. Give the formula and valency of :
(a) aluminate
(b) chromate
(c) aluminium
(d) cupric
9. (a) What is a chemical formula ? (b) What is the
significance of a formula ? Give an example to illustrate.
10. What do you understand by the following terms ?
(a) Acid radical (b) Basic radical
11. Select the basic and acidic radicals in the following
compounds.
(a) MgSO4
(b) (NH4)2SO4
(C) Al2(SO4)3 (d) ZnCo
(e) Mg(OH)2
12. Write chemical formulae of the sulphates of Aluminium,
Ammonium and Zinc.
13. The valency of an element A is 3 and that of element B
is 2. Write the formula of the compound formed by the
combination of A and B.​

Answer 1

Answer:

1. The first letter/ first two letters of the Latin/Greek(most time) name of a chemical element is Symbol. ... It conveys the definite identity of chemical element in shorter and scientific way. It also provide the easiest way to know Atomic Number of any element.
2. The symbols for the elements are derived from their Latin and Greek synonyms to avoid confusion due to English words. For Sodium the symbol is Na derived from Natrium, because the symbol S was already taken for Sulphur so Si is the symbol for Silicone.
3. A chemical nomenclature is a set of rules to generate systematic names for chemical compounds. The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC).

The wrong thing in writing cobalt as CO is that we can't write o as O because O represent Oxygen and symbols representing an element with two letters have first one as capital and next one should be in small letter.

5. H2 means two hydrogen atoms. O2 means two oxygen atoms. The number before the element is the number of molecules. 2H2 means two molecules of hydrogen and four hydrogen atoms.

6. Atomicity is defined as the total number of atoms that constitute a molecule. ... Diatomic-composed of 2 atoms e.g. H2 , N2 , O. Triatomic-composed of 3 atoms e.g. O. 3. Polyatomic-composed of 3 or more atoms e.g. P4 , S.

7.A) The combining power or the combining capacity of an atom or an element is called its valency. Valency of an element is decided by numer of outermost shell electrons. If an element exhibit more than one valency . This is known as variable valency

B) For example, the valency of Hydrogen is 1 as it has one electron in its outermost shell and requires one electron to become stable. Some elements differ in their capacity to combine with other elements depending on the nature of the reaction; this property is called variable valency

8 in photo

9 chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.

(B) Formula also represents one mole of molecules of the substance. That is, formula also represents 6.022 × 1023 molecules of the substance. Formula gives the name of all the elements present in the molecule. Formula gives the number of atoms of each element present in one molecule.

10 The ion formed after removal of Hydrogen ion (H+) from an acid is called acid radical. ... The ion formed after removal of hydroxyl ions (OH-) from a base is called basic radical.

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