Mention three gaseous elements and write their molecular formulae.

What is a molecular formula?

Based on the group valency of elements write the molecular formula of the following compounds giving justification for each: (i) Oxide of first group elements. (ii) Halide of the elements of group thirteen, and (iii) Compounds formed when an element, A of group 2 combines with an element, B of group seventeen.

What are synthetic elements ? Mention two synthetic elements and write the nuclear equations leading to their synthesis.

Indicate wheter the following pairs of elements form ionic or covalent compounds Also write their molecular formula (a) C and S (b) Na and CI (c ) S and O (d) Ca and H .

The glucose has the molecular formula?

An element P(atomic number 20) reacts with an element Q (atomic number 17) to form a compound. Answer the following questions giving reasons : (a) Write the positions of P and Q in the Modern Periodic Table. (b) Write the molecular formula of the compound when P reacts with Q.

Write the structure of eh isometric adehydes and ketones with the molecular formula C_(5)H_(10)O . Give their IUPAC names.

The commonest disaccharide has the molecular formula?

Correct the following statement: An element is represented by molecular formula.

Write the names and structures of three isomers which have the same molecular formula C_(4)H_(8)O .