Lithium burns in air to form lithium oxide, but sodium reacts with oxygen to form a mixture of sodium oxide and sodium peroxide.
lˈɪθiəm bˈɜːnz ɪn ˈɛɹ tə fˈɔːɹm lˈɪθiəm ˈɑːksaɪd, bˌʌt sˈoʊdiəm ɹɪˈækts wɪð ˈɑːksɪdʒən tə fˈɔːɹm ɐ mˈɪkstʃɚɹ ʌv sˈoʊdiəm ˈɑːksaɪd ænd sˈoʊdiəm pəɹˈɑːksaɪd.