Fill in the blanks.
(a) Hydrogen is ___ than air.
(b) Hydrogen is ___ soluble in water.
(c) Hydrogen burns with a ___ flame and ___ sound is heard.
(d) A Metal ___ hydrogen in the reactivity series gives hydrogen with ___
(e) Hydrogen reacts with metal oxides to form ___ and ___
(f) Oxidation is the removal of ___ or addition of ___
(g) In redox reactions oxidation and reduction occur ___