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Chapter 3.3 The number of protons in the nucleus of each atom of that element. Total number of protons and neutrons in the nucleus of an isotope. Mass Number ---> 12 C Atomic Number ---> 6C General term for any isotopes of any element Grams is too large for a unit to use for measuring the mass of an element. Scientists use one element to be the standard for atomic mass -- carbon 12 carbon 12 = 12 atomic mass units 1 u is equal to 1/12 the mass if a carbon 12 atom (1.6605402 x 10 g Atomic mass - the mass of an atom expressed in atomic mass units. Relative atomic mass of atoms of that nuclide Most element occur naturally as mixtures of isotopes - % nearly always the same Atomic Masses on the periodic table are averages (weighted averages) of the isotopes Defined as weighted average of the atomic masses of the naturally occurring isotopes of an element The amount of a substance that contains the same number of particles as the number of atoms in exactly 12g of carbon 12 SI unit for amount of a substance abbreviation (mol) Counting unit like dozen 6.022 x 10 is the number of particles in exactly one mole of a pure substance 12g of carbon 12 = 1 mol = 6.022 x 10 atoms Mass in grams of one mole of a pure substance. Molar mass of an element = atomic mass of the element in atomic mass units Li - 6.941 g Hg - 200.59 g EX: What is the mass in grams if 3.50 mol x 63.5g Cu/1 mol Cu = Answer - 222 g Cu |
