Two key factors that contribute to the ease of deprotonation are the polarity of the H—A bond and the size of atom A, which determines the strength of the H—A bond.
tˈuː kˈiː fˈæktɚz ðæt kəntɹˈɪbjuːt tə ðɪ ˈiːz ʌv dᵻpɹˌoʊtənˈeɪʃən ɑːɹ ðə poʊlˈæɹᵻɾi ʌvðɪ ˈeɪtʃ—ɐ bˈɑːnd ænd ðə sˈaɪz ʌv ˈæɾəm ˈeɪ, wˌɪtʃ dɪtˈɜːmɪnz ðə stɹˈɛŋθ ʌvðɪ ˈeɪtʃ—ɐ bˈɑːnd.