1. Isotopes

2. Atomic Number • Atomic number = number of protons • Which makes it always a whole number • Atomic number is always the same for a given element • Can be found on the periodic table

3. Isotope • Atoms of the same element with different number of neutrons • They have different mass numbers • They have the same number of protons • Nuclide • General name for an isotope of an atom

4. Mass Number • Atoms of the same element may have different numbers of neutrons • Mass number • Sum of protons + neutrons • Mass number can not be found on the periodic table • Not found by rounding atomic mass • Given through words or symbols

5. Atomic Mass • Weighted average of the masses of naturally occurring isotopes of an element • Can be found on the periodic table • It is not usually a whole number

6. Calculating Average Atomic Mass • Depends on both mass and relative abundance • How do you find average atomic mass? • Naturally occuring copper consists of 69.15% copper-63 which has an atomic mass of 62.929601 amu and 30.85% copper-65 which has an atomic mass of 64.927794 • Multiply the atomic mass of each isotope by its relative abundance(expressed as a decimal) and add the results • 0.6915 x 62.929601 amu + 0.3085 x 64.927794 amu = 63.55 amu

7. Calculating average atomic mass • Three isotopes of Argon occur in nature. Calculate the average atomic mass of Argon to decimal places: Argon-36 (35.97 amu; 0.337%) Argon-38 (37.96 amu; 0.063%) Argon-40 (39.96 amu; 99.600%) Answer: 39.95 amu

8. Isotopes of Hydrogen • Protium • Deuterium • Tridium

9. Isotopes of Hydrogen faculty.weber.edu/bdattilo/shknbk/notes/time.htm

10. Isotopes • Hydrogen isotopes are different because most isotopes do not have their own specific name • They are identified by their mass number

11. C 12 6 Illustrating isotopes/nuclides Nuclear Notation: Hyphen Notation: C-12

12. Isotope Stability • Stable nucleus • a correct ratio of neutrons and protons should be present in the nucleus. • Unstable nucleus • radioactive • Elements 83-112  radioactive • Elements 93-112  man-made

13. 1. Sodium-23 2. calcium-40 3. Cu 4. Ag 64 Problems – determine the # of p+, n, and e- in each of these. 1. 11 p+, 11 e-, 12 n 2. 20 p+, 20 e-, 20 n 3. 29 p+, 29 e-, 35 n 4. 47 p+, 47 e-, 61 n 29 108 47

14. Problems – write the nuclear notation and hyphen notation for • 5. mass number 28, atomic number 14 • 6. 26 protons and 30 neutrons • 7. 56 electrons and 82 neutrons

15. Answers • 5. 14Si silicon-28 • 6. 26Fe iron-56 • 7. 56Ba barium-138 28 56 138