 Protons, neutrons, electrons too  Make up the atoms all around you!

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 Protons, neutrons, electrons too  Make up the atoms all around you!

 Nucleon – general term for nuclear particles.  What are nuclear particles?  Protons – positively charged particles in the nucleus of an atom that identifies the element: atomic number on the periodic table: has a mass of ~1 amu  Neutrons – neutral particles in the nucleus of an atom: number may vary: has a mass of~ 1 amu

 Electrons – negatively charged particles found in orbitals outside the nucleus (electron cloud): determines the reactivity of the atom: have virtually no mass ( 1/1840 amu)  Sum of protons and neutrons gives the mass number (weight) of the atom  amu is based on 1/12 of the carbon-12 atom – a reference isotope

 What’s an isotope?  Atoms of the same element having different numbers of neutrons (therefore different masses) are called isotopes.  They have the same number of protons (identity stays the same).

 Ex. Hydrogen has 3 isotopes  hydrogen – 1, hydrogen – 2, and hydrogen -3  May be represented several ways.  H-1, hydrogen-1, 1 H 1, 1 H, (nuclide)  Mass number as a superscript and atomic number as a subscript. May see both on the left side of element symbol.  Which do you think is the most abundant isotope? (hint: look at the periodic table)

 Mass number on the periodic table is actually the average atomic mass – a weighted average based on the percent abundance of the naturally occurring isotopes. That’s why they almost always have decimals!  A mass number is usually a whole number, sum of protons and neutrons – can’t have just a piece of a neutron or proton in an atom.

 Copper exists as a mixture of two isotopes.  Cu-63 makes up 69.17% of copper atoms and Cu-65 makes up 30.83% of copper atoms. If the atomic mass of Cu-63 is 62.930 amu and the atomic mass of Cu-65 is 64.928 amu, calculate the average atomic mass of copper based on the percent abundance of the two isotopes.

Isotope AbundanceAtomic mass (amu) Ga-6960.108%68.926 Ga-7139.892%70.925

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