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Basic Atomic Structure. 1/16/09. I . Subatomic Particles subatomic particle = a particle found inside the atom nucleus = small, dense area in center of atom (p + & n 0 found here). amu (atomic mass unit) = exactly 1/12 the mass of carbon-12 atom.
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Basic Atomic Structure 1/16/09
I. Subatomic Particles • subatomic particle = a particle found inside the atom • nucleus = small, dense area in center of atom (p+ & n0 found here). • amu (atomic mass unit) = exactly 1/12 the mass of carbon-12 atom. • in a neutral atom, number of p+ = number of e- (# of n0 varies). • isotope= a variety of an atom that contains a different number of neutrons compared to others (still has same number of p+).
II. Describing the Atom • atomic symbol = a capital letter (or 1 capital, 1 lowercase) that symbolizes an element. Usually comes from current name, but can also originate from another language. • isotopic notation = way of writing the symbol to include the number of protons and neutrons (in nucleus). • C = (just symbol for carbon) • carbon-12 = form of carbon with 12 total particles in the nucleus. • C-12 = another way to write #2 (using symbol instead of name) • 12C =another wayto write #2 (must beinupper-left-hand corner)
III. Atom Numbers • atomic number = number of p+. Written in bottom-left-hand corner of symbol. Identifies the element. • mass number = number of p+ & n0. Identifies the isotope. Written in top-left-hand corner. • atomic mass (or weight) = weighted average of all the mass numbers of all the isotopes of an element. Not written on symbol, but is found on PT. 14 6 C Carbon 6 C 12.01 • atomic mass is calculated by multiplying the mass number of each isotope by its abundance in the environment (a percentage).
atomic mass is calculated by multiplying the mass number of each isotope by its abundance in the environment (a percentage). Ex: hydrogen has three isotopes… 1. protium (1 p+, 0 n0) @ 99.985% 1.0078 amu x 0.99985 = 1.007648830 amu 2. deuterium (1 p+, 1 n0) @ 0.0149% 2.0141 amu x 0.000149 = 0.000300101 amu 3. tritium (1 p+, 2 n0) @ 0.0001% 3.016 amu x 0.000001 = 0.000003016 amu 1.007951947 amu ≈ 1.008 amu Hydrogen 1 H 1.008
atomic mass tells you two very important things about an element: 1. the mass of one atom of an element, measured in amu. • hydrogen = 1.008 amu per atom • carbon = 12.01 amu per atom • gold = 196.97 amu per atom
2. the mass of one mole of an element, measured in grams. • hydrogen = 1.008 grams per mole • carbon = 12.01 grams per mole • gold = 196.97 grams per mole
mole = a counting unit (like “dozen” or “gross”), representing 6.022 x 1023 particles of an element/compound. One mole of ANY element/compound will contain 6.022 x 1023particles. • Avogadro’s number = number of atoms found in exactly 12 grams of carbon-12, which is (surprise!)6.022 x 1023. 602,200,000,000,000,000,000,000 Let’s see if you can incorporate what you’ve learned...
