This quantity decreases going down the group, and so does the activation energy; thus, chemical reactions can occur faster and the reactivity increases down the group.
ðɪs kwˈɔntᵻɾi dˈiːkɹiːsᵻz ɡˌoʊɪŋ dˌaʊn ðə ɡɹˈuːp, ænd sˌoʊ dˈʌz ðɪ ˌæktɪvˈeɪʃən ˈɛnɚdʒi; ðˈʌs, kˈɛmɪkəl ɹɪˈækʃənz kæn əkˈɜː fˈæstɚ ænd ðə ɹɪɐktˈɪvᵻɾi ˈɪŋkɹiːsᵻz dˌaʊn ðə ɡɹˈuːp.