Why do electrons enter the 4s orbital before entering the 3d orbital?

Which of the following statements is true? a. elements in the last period are radioactive. b. atomic weight is the same as atomic mass. c. elements in the same group have the same number of electron shells. d. atomic number equals the number of neutrons in the nucleus of an atom.

In the following redox reaction which is the oxidizing agent and which is the reducing agent? alcl3 + na nacl + al oxidizing agent = reducing agent =

How many absorptions would you expect to observe in the 13c nmr spectra of the following molecules? a) 3-chloropentane b) cis-4-methyl-2-pentene