Compare the acidic strengths of the hydrides in periods and groups.

Explanation

In periods, the acidic strength increases in the order, `CH_4 lt NH_3 lt H_ 2O lt HF `
Acidic strength of non-metal hydrides increases with increase in the electronegativity of elements forming the hydrides. Methane almost has no acidic nature. Hydrogen fluoride is a clear proton donor in aqueous solutions.
But in groups H-Abond strength is more important factor in detemining the acidity than its polar nature. As the size of A increases down the group, H-A bond strength decreases and the acidic strength increases. eg. Acidic strength order of hydrogen halides is `HF lt HCI lt HBr lt HI`