2. Proton A positively charged subatomic particle (found in the nucleus). A subatomic particle with no charge (found inside the nucleus). Neutron

3. Atomic Number The number of protons in the nucleus of an atom of that element. (This is also the number of electrons) Element# of protonsAtomic # Carbon66 Phosphorus15 Gold79 Atomic number

4. Element’s Name Atomic # Symbol Atomic Mass

5. Mass Number Mass number is the number of protons and neutrons in the nucleus of an isotope. Mass # = p + + n 0 Nuclidep+p+ n0n0 e-e- Mass # Oxygen - 8 - 33 - 3015 8816 Arsenic663366 Phosphorus153015

6. NuclideAtomic Number Mass Number #Protons#Electrons#NeutronsHyphen Notation Nuclear Notation Calcium – 41 20 Barium - 5683 Tin - 118 50 137 Oxygen – 17 9 Helium –4 4

7. Mass Number & Atomic Mass The number of protons (+) and electrons (-) in an atom are the same (as long as the atom is neutral). The number of protons and neutrons (0) is not always the same.

8. Isotopes Isotopes are atoms of the same element that have diff. masses because of diff. numbers of neutrons. IsotopeProtonsElectronsNeutronsNucleus Hydrogen–1 (protium) 110 Hydrogen-2 (deuterium) 111 Hydrogen-3 (tritium) 112

9. Warm Up 9/16 If you have a 65 formative average and a 72 summative average, what would your grade be?

10. Avg. Atomic Masses IsotopeSymbolComposition of the nucleus % in nature Carbon-12 12 C6 protons 6 neutrons 98.89% Carbon-13 13 C6 protons 7 neutrons 1.11% Carbon-14 14 C6 protons 8 neutrons <0.01% Atomic mass is the average of all the naturally occurring isotopes of that element. Carbon = 12.011 6 6 6

11. Practice 1.What is the average atomic mass of Lithium if 7.42% exists as Li and 92.58% exists as Li? 2.Find the average atomic mass: 78.70% Mg, 10.03% Mg, 11.17% Mg 6 7 24 25 26