If an isotope of hydrogen has two neutrons in its atom,its atomic number and atomic mass number will respectively be

Which element forms the maximum number of compounds in chemistry?

The element used for welding metals with high melting points is:

What is the sum of the number of neutrons and protons in the heaviest isotope of hydrogen?

In which of the following reactions,hydrogen is evolved?
$I$. Reaction of sodium borohydride with iodine
$II$. Oxidation of diborane
$III$. Reaction of boron trifluoride with sodium hydride
$IV$. Hydrolysis of diborane

Give the uses of $Dihydrogen$.