Question

why copper become green if it Left Open in air why​

Answer 1

Copper turns green because of chemical reactions with the element Just as iron that is left unprotected in open air will corrode and form a flaxy orange red outer layer , copper that is exposed to the elements undergoes a series of chemical reactions that give the shiny metal a pale green outer layer called a patina .

Answer 2

Just like iron it corrodes in air and a pale green layer called patina is formed.