1. mass # atomic # protons + neutrons = protons = Atomic Symbols

2. ElementAtomic Number ProtonsNeutronsElectrons 19 20 S17 39 Ca 14 6 K 19 39 16 33 20 1920 668 6 C Elements are identified by atomic number (protons).

3. 1111 H 2121 H 3131 H protium deuteriumtritium element: mass: _________: same or different same # of protons & electrons, BUT different # of neutrons Isotopes

4. 1.The number of protons in the nucleus is… A.the mass number. B.the atomic number. C.the same as the number of neutrons. D.the total of protons and neutrons. Quick (but challenging) Quiz!

5. 2.The mass number is… A.the number of protons. B.the number of neutrons. C.the total of protons and electrons. D.the total of protons and neutrons. Quick (but challenging) Quiz.

6. 3. Isotopes of an element have… A.the same mass number. B.different atomic numbers. C.the same number of protons but different mass numbers. D.the same number of protons but different numbers of neutrons. Quick (but challenging) Quiz.

7. 4. How many neutrons are in an atom of potassium–40 ? ( 40 K) (Atomic Number = 19) A.19 neutrons B.21 neutrons C.40 neutrons D.59 neutrons Quick (but challenging) Quiz.