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

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

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. 5. 14 Sisilicon-28 6. 26 Fe iron-56 7. 56 Ba barium-138 138 28 Answers 56