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ISOTOPES!. What is the average number of fingers on one human hand?. Data: 6,000,000 people have 5 fingers, 240,000 people have 4 fingers and 1,800 people have 6 fingers (*NOTE: Mrs. Baker made this data up: I’m sure there are people with 0, 1 & 2 fingers). Review
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What is the average number of fingers on one human hand? Data: 6,000,000 people have 5 fingers, 240,000 people have 4 fingers and 1,800 people have 6 fingers (*NOTE: Mrs. Baker made this data up: I’m sure there are people with 0, 1 & 2 fingers)
Review • All atoms of an element have the same # of protons (EXAMPLE: EVERY SINGLE CARBON ATOM IN THE WORLD HAD 6 PROTONS) • However, atoms of the same element can have different numbers of neutrons • Since mass = p + n, these atoms have different mass numbers
Isotope: An atom with the same number of protons, but a different number of neutrons. C-12 C-13 C-14 12 13 14 C C C 6 6 6 6 p+, 6 n 6 p+, 7 n 6 p+, 8 n 12.011—average atomic mass
How do we measure the mass of a tiny atom? Atomic mass units (amu): The mass of a single atom is called its atomic mass and units are labeled “amu”. 1 amu is = to 1/12 of a carbon atom with a mass # of 12. (6 protons @ 1 amu each + 6 neutrons @ 1 amu each = 12 amu)
225,000,000,000,000,000,000,000,000 amu = 1 pound!!!!!!!!!!!!!!!!!!!!!
You’ll often see elements written like this: Mass Number 23 Na 11 Atomic number
Naming Isotopes • Scientists usually name isotopes by their mass #. Example: Cobalt-60 (60 = the mass number) You try: Ex #1: How would you write the name and symbol for a neon atom with 10 protons and 11 neutrons? Ex #2: How would you write the name and symbol for an atom with 15 protons and 17 neutrons?
How do you calculate average atomic mass? (atomic mass)(relative abundancy) + (am)(ra) + … Example: Oxygen Oxygen-16 mass = 16, 99.759% Oxygen-17 mass = 16.995, 0.037% Oxygen-18 mass = 17.995, 0.207% (15.995)(0.99759) + (16.995)(0.00037) + (17.995)(0.00207) = 15.99998985
Let’s do a problem! Unknown Element X has 2 isotopes Mass= 12.00000g, 98.89% 13.00335g, 1.11% What is the mystery element X? (12.0000)(0.9889) + (13.00335)(0.0111) 12.011 Carbon