Question

Chemistry:
1. Write 1 to 30 elements symbols and atomic numbers 3 times.
2. Find out the formula of the following compounds.
(A) Water (B) Salt (C) Sugar (D) Carbon dioxide (E) Carbon monoxide (F) Vinegar
(G) Washing soda (H) Baking soda (I) Hydrochloric acid (J) Magnesium chloride
3. Prepare a poster on ways of ‘saving water’.
4. Write short note on compounds and mixtures.
5. What is the difference between the symbol and the formula of oxygen?
6. Most elements are found in the Free State in nature. Do you agree? Give reasons.
7. Write the valencies of some common elements and groups
(i) Hydrogen (ii) Oxygen (iii) Aluminium (iv) Carbon (v) Nitrogen (Vi) Sulphur (vii) Iron (viii) Phosphate
(ix) Chlorine (x) Iodine
8. What is a chemical equation? Why is it necessary to balance an equation?
9. Define the following
(a).Atomicity (b).Valency (c).Symbol
10. What information does a formula give?

Answer 1

formula of water is H2O salt naal carbon dioxide CO2 carbon mono oxide CO

Answer 2

What is valency ?

=> Valency is the combining capacity of an atom with another atom (s) .

This is normally given by the number of Valence electrons or by 8 minus the Valence electrons (Only when the number of Valence electrons is more than 4) .

Valency of first 20 elements is given below.
1) Hydrogen (H) = 1

2) Helium (He) = 0

3) Lithium (Li) = 1

4) Beryllium (Be) = 2

5) Boron (B) = 3

6) Carbon (C) = 4

7) Nitrogen (N) = 3

8) Oxygen (O) = 2

9) Fluorine (F) = 1

10) Neon (Ne) = 0

11) Sodium (Na) = 1

12) Magnesium (Mg) = 2

13) Aluminium (Al) = 3

14) Silicon (Si) = 4

15) Phosphorus (P) = 3, 5

16) Sulphur (S) = 2

17) Chlorine (Cl) = 1

18) Argon (Ar) = 0

19) Potassium (K) = 1

20 ) Calcium (Ca) = 2

#Be Brainly !!