Name a gaseous element whose molecule and atom are identical.

Two strands of DNA molecules are identical.

Name two micro elements.

Name an atom in which the molecules of that atom does not contain any neutrons?

Name an inert radio element.

Name the main element of biogas.

Name a bivalent element whose oxide is soluble in excess NaOH solution.

Name the element whose positon in the periodic table is still controversial.

Name two crystalline elements.

State the group number in the modern periodic table where solid, liquid and gaseous elements are present at ordinary temperature. Identify the solid and liquid elements.