1. Isotopes

2. Subatomic Particles # protons = atomic number Carbon - atomic number 6; # of protons 6 # electrons (neutral atom) = # protons Carbon - # protons 6 = # electrons 6 # neutrons = mass number – atomic number Carbon-12 6 neutrons = 12 (mass number) – 6 (atomic number)

3. ATOMS OF THE 1 ST TEN ATOMS NAMESYMBOL ATOMIC # p+p+p+p+ n0n0n0n0 MASS # e-e-e-e- HydrogenH11011 HeliumHe22242 LithiumLi33473 BerylliumBe44594 BoronB556115 CarbonC666126 NitrogenN777147 OxygenO888168 FluorineF9910199 NeonNe1010102010

5. Isotope: two or more atoms having the same number of protons but different numbers of neutrons or Na-23 or Na-24

6. Every Cl atom has 17 protons, w/o exception, but not every Cl atom has 18 neutrons. – Atoms with the same # of protons but contain different #s of neutrons are called isotopes. Since isotopes of an element have different #s of neutrons they have different masses

7. Isotopes are chemically alike because they have identical numbers of protons and electrons – It’s the electrons and protons that are responsible for chemical behavior Isotopes can be noted using hyphen notation (Cl-35 vs. Cl-37) or (Chlorine – 35 vs. Chlorine – 37) – element symbol hyphen mass number – element name hyphen mass number

8. Hydrogen Isotopes Nuclide #p+ #n 0 # e- at. # mass number (#p+ and #n0) Protium 1 0 1 1 1 (1 + 0) Deuterium 1 1 1 1 2 (1 + 1) Tritium 1 2 1 1 3 (1 + 2)

9. 9 H 3 1 H 2 1 H 1 1 Hydrogen Isotopes

10. Write the hyphen notations for the following:

11. Average Atomic Mass This is the mass that is on the periodic table. It is a weighted average of the masses of all the isotopes of a particular element. Atomic mass = (mass isotope 1)(% abundance) + (mass isotope 2)(% abundance) +..... This is what is located on the periodic table

12. Practice 1.Naturally occurring chlorine is 75.53% chlorine- 35 and 24.47% chlorine-37. What is the average atomic mass? Ans. (0.7553)(35) + (0.2447)(37) = 1.The element Neon consists of three isotopes with masses 19.99, 20.99, and 21.99 amus. These three isotopes are present in nature to the extent of 90.51%, 0.27%, and 9.22% respectively. Calculate the atomic mass of neon.

13. Isotopes of Neon Isotopes% in Nature Atomic Number Atomic Mass (amu) 1 atom Mass Number Average Atomic Mass (amu) Ne-2090.51%1019.99244 amu 2020.183 amu Ne-210.27%1020.99395 amu 21 Ne-229.22%1021.99138 amu 22

14. 3.The element silver exists in nature as two isotopes Ag-107 and Ag-109. The accepted atomic mass of silver is 107.87amu. What isotope is more abundant?

15. 4.Calculate the average atomic mass of an element given the following information: Nitrogen-15 is 30% abundant Nitrogen-13 is 20% abundant Nitrogen-14 is 50% abundant