For an object to be seen, light must leave ___ and enter ___. A. the eye; the brain

B. the object; the eye

C. the eye; the object

D. the brain; the eye

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8