Understand it from this compound:

HC (TRIPLE BOND) CH.  called ethyne or acetylene.

the hybridisation of carbon in this is sp. therefore it has 50% s character. there are 2 pi bonds and one sigma bond, so there is electron cloud above and below the molecular plane, making it highly electro negative.

Since the carbon becomes highly electronegative, it tends to attract electron pair towards itself from its Bond with hydrogen. So, Carbon will gain a partial negative charge and hydrogen will get a partial positive charge.  and bond becomes weaker. hence, in presence of a proton loving reagent, the H+ can easily leave ethyne.

That is why we say that H has become acidic and we call it Acidic Hydrogen in all similar types of compound.

Got it?

hiiii

An acidic hydrogen atom is a hydrogen atom that has lost its electron and

is running around as a hydrogen ion. The lone proton (in 1H) has loaned out

its electron in a chemical reaction, like to chlorine in HCl, and when HCl is

combined with water, the H and the Cl separate into H+ and Cl- ions. That

H+ ion is the acidic hydrogen atom   !!!!