Name the acid whose formula is ${\mathrm{H}}_2{\mathrm{CO}}_3$.

State which element exists in the highest percentage in
(i) Earth's crust

(ii) Atmosphere

(iii) Human body.

Give the symbols of the following elements and state in each case whether they are metals, non-metals, metalloids or noble gases.

a) Potassium
b) Carbon
c) Oxygen
d) Mercury
e) Fluorine
f) Neon
g) Sulphur
h) Zinc
i) Boron
j) Copper
k) Calcium
l) Xenon
m) Arsenic
n) Mercury
o) Chlorine
p) Silicon
q) Neon
r) Lead
s) Antimony
t) Sodium
u) Iodine
v) Platinum

w) Radon
x) Phosphorus
y) Bromine
z) Aluminium.