Eyona nto yakhelwa kuyo nesisiseko se-element ibizwa ngokuba yi-atom. I-atom sisiseko sokwakhela nesisesona sakhe sasincinane kangangokuba xa ufuna ukuyibona ungayisika i-element ungakhange ude ube uyayicukuceza (uyijike ibe yi-element ekhaphukhaphu, umzekelo ngenuclear fission okanye ngeradioactive decay). I-chemical compound yi-substance eyenziwe ngee-elements ezimbini nangaphezulu. Kwi-compound, ii-atoms ezimbini nangaphezulu zithi zimanyane zenze i-molecule. Intlantsana yothulu okanye intwana yeqabaza lento engamanzi eli libonwa ngamehlo lenziwe nezigidi ngezigidi okanye ngezigidigidi zezi molecules. Imixube ziisubstances apho ii-chemicals are zixutywe khona kodwa zibe zingenantshukumo ziyenzayo okanye ibonakalayo. Umzekelo ngowaxa kudityaniswa isanti netyuwa. Oku kunokujikwa kwakhona kwenziwe ityuwa nesanti ngokwahlukana kwazo. Ii-Chemical compounds zitshintshwa yi-chemical reaction. Umzekelo ingakukutshisa i-sodium bicarbonate, i-baking powder le siyaziyo. kugalelwa amanzi, i-carbon dioxide, kunye nesodium carbonate. Lo mxube awunakujikwa okanye ezi zinto azinakwahlukaniswa.