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How Atoms Differ

How Atoms Differ. Mr. E Chemistry. Atomic Number = number of protons in the nucleus of an atom. It really is the identity of the element. What did you discover yesterday when you changes the amount of protons in an atom? The atomic number identifies the element. C

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How Atoms Differ

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  1. How Atoms Differ Mr. E Chemistry

  2. Atomic Number = number of protons in the nucleus of an atom • It really is the identity of the element. What did you discover yesterday when you changes the amount of protons in an atom? • The atomic number identifies the element. C The # of electrons equals the number of protons in an atom. If the number of protons does not equal the number of electrons we call it an ion. Not all atoms of an element are identical. The different versions of an element are called isotopes. 6

  3. Isotope = atoms of the same element with different numbers of neutrons Ex: Carbon ~95% C ~5% C 12 6 14 6 BUT Protons = Neutrons = Protons = Neutrons =

  4. Mass Number = # of protons + # of neutrons in a single atom - Different isotopes have different mass numbers - NOT on the periodic table! Ex: K Mass Number 39 Protons = Neutrons = Mass Number = 19 Atomic Number

  5. Atomic Mass Unit (amu)= defined as 1/12 the mass of a carbon-12 atom Composed of 2 particles: • Proton = positive charge • - mass of 1.673 x 10-24 g = 1 amu (atomic mass unit) • 2)Neutron = neutral, no charge • - 1 amu

  6. Average Atomic Mass (or Atomic Mass)= weighted average of all the isotopes of an element How to calculate it: Chlorine-35 Chlorine-37 Atomic Mass = 34.969 amu Atomic Mass = 36.966 amu 75.770% abundance 24.230% abundance The average atomic mass of chlorine is closer to the mass of chlorine-35 because chlorine-35 is much more abundant in nature.

  7. % Abundance Equation

  8. Electrons = negatively charged particle - mass = amu … basically no mass! - Charge = # of protons - # of electrons Ex: Li Mass Number 7 Charge 3 If there is nothing in the charge position, the atom has 0 charge = neutral! Atomic Number Protons = Neutrons = Electrons=

  9. Ex: 24 +2 Protons = Neutrons = Electrons= Mg 12 36 -1 Protons = Neutrons = Electrons= Cl 17

  10. Ex: 24 Protons = Neutrons = Electrons= 10 Na Protons = Neutrons = 16 Electrons= 18 S

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