How to write the chemical formulae

Why does the number of chlorine atoms differ in these compounds? Try to find out by analysing the valency of the elements Na,Al,Cl and C . Analyse Table Examine the above table and identify how t write the chemical formula from valency. Compare your findings with the following. First write the element with lower elctronegativity. Exchange the valency of each element and write as sufix. Divide the suffix with the common factor. If the suffix is 1, it need not be written. .

write the chemical formula of oleum?

What is rust?Write the chemical formula .

Write the chemical formula of urea.