Organic chemistry refers to the branch of science that deals with which element? oxygen nitrogen carbon aluminum

Organic  chemistry  is a branch  of science that deal  with carbon element

   organic  chemistry  is a sub discipline of chemistry which involve  the scientific  study of the structure,properties and reactions of organic  compounds, that is  compound  that contain carbon atoms. Carbon atom  form  covalent  bond  with itself and other element to create a mind boggling  array   of structure which  is  studied in organic chemistry  sub discipline 

☆ionisation energy increases across a period from na -> ar☆ionisation energy decreases down a group from li -> fr☆ionic radius decreases across a period from na -> cl☆ionic radius increases down a groupfrom f -> ii hope it clarifies your doubts