A.12克 B.12 C.1.66×10-27千克 D.1.66×10-27
A.12 B.14 C.16 D.18
A.質(zhì)子數(shù)為20 B.電子數(shù)為20 C.中子數(shù)為20 D.質(zhì)量數(shù)為20