Nitrogen is an unreactive gas because breaking the strong triple bond in the dinitrogen molecule (N2) requires a lot of energy.
nˈaɪtɹədʒən ɪz ɐn ʌnɹɪˈæktɪv ɡˈæs bɪkˈʌz bɹˈeɪkɪŋ ðə stɹˈɔŋ tɹˈɪpəl bˈɑːnd ɪnðə dˈɪnaɪtɹədʒən mˈɑːlɪkjˌuːl ˈɛn tˈuː ɹᵻkwˈaɪɚz ɐ lˈɑːt ʌv ˈɛnɚdʒi.