Unformatted text preview: hemistry 101 Chapter 2 ISOTOPES
· Atoms with the same number of protons (same Atomic Number, Z) but different number of neutrons (different Mass Number, A) are called isotopes.
· Most of the elements occur in nature as mixtures of isotopes.
· Naturally occurring copper is found to contain 2 isotopes: 63
29 C u Isotope C u 29 protons 34 neutrons Nuclear Particles Relative Abundance Relative Atomic Mass 29 protons 36 neutrons 69.09 % 30.91 % 62.9298 amu 64.9278 amu 63.55 amu Average Atomic Mass Isotopes & Atomic Mass: · The mass of an atom is measured relative to the mass of a chosen standard (carbon12 atom), and is expressed in atomic mass units (amu).
· The average atomic mass of an element is the weighted average for the mass of all the naturally occurring isotopes of that element expressed in atomic mass units (amu).
· Therefore the atomic mass of an element is closest to the mass of its most abundant isotope.
· As a...
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