Which of the following symbols of elements are incorrect? Give their correct symbols

(a) Cobalt	CO
(b) Carbon	C
(c) Aluminium	AL
(d) Helium	He
(e) Sodium	So

Write the cations and anions present (if any) in the following compounds

(a) CH₃COONa

(b) NaCl

(c) H₂

(d) NH₄NO₃

Give the formulae of the compounds formed from the following sets of elements

(a) Calcium and fluorine

(b) Hydrogen and sulphur

(c) Nitrogen and hydrogen

(d) Carbon and chlorine

(e) Sodium and oxygen

(f) Carbon and oxygen

Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them. (You may use appendix-III).

(a) Ammonia

(b) Carbon monoxide

(c) Hydrogen chloride

(d) Aluminium fluoride

(e) Magnesium sulphide

State the number of atoms present in each of the following chemical species

(a) CO₃^2-

(b) PO₄^3–

(c) P₂O₅

(d) CO