Which of these has the lowest first-ionization energy? A) Cs
B) Ag
C) Pb
D) Br
E) Se

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.

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.