11. Explain how a mass number is different than an atomic mass. 12. Describe the difference between the following pairs of atoms at the st a. 3580Br&3579Br b. 3579Br& 13. Give both the name and the symbol for the elements that fits the foll a. The halogen in period 4 b. The alkaline earth metal in period 2 c. The noble gas in period 5 d. The transition metal in period 5 , group 1B