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					Atoms, Ions, and Isotopes
      Atoms, Ions, and Isotopes
• All matter is composed of particles called atoms.




• An atom is the smallest unit of an element that
  carries the general properties of that element.

• Atoms are composed of subatomic particles.

• The three most important subatomic particles
  are protons, neutrons, and electrons.
      Atoms, Ions, and Isotopes
• A proton is a subatomic particle that has a
  charge of +1.

• A proton is a subatomic particle that has a mass
  of ≈1 amu (amu = atomic mass unit).

• A proton can be symbolized two different ways!
                letter symbol: p
                       or
           the mass-charge symbol:        1 H
                                           1
     (the superscript = mass & the subscript = charge).
       Atoms, Ions, and Isotopes
• A neutron is a subatomic particle that has a
  charge of 0 (zero).

• A neutron is a subatomic particle that has a
  mass of ≈1 amu (In reality, a neutron is slightly
  more massive than a proton).

• A neutron can be symbolized two different ways!
                 letter symbol: n
                        or
            the mass-charge symbol: 10n
      (the superscript = mass & the subscript = charge).
       Atoms, Ions, and Isotopes
• An electron is a subatomic particle that has a
  charge of -1.

• An electron is a subatomic particle that has a
  mass of ≈0 amu (In reality, an electron does have
  a very very very very small mass).

• An electron can be symbolized two different ways!
                 letter symbol: e-
                        or
            the mass-charge symbol:        0
                                               -1e
      (the superscript = mass & the subscript = charge).
       Atoms, Ions, and Isotopes
• The subatomic particles in order of increasing
  mass: electron → proton → neutron.

Ex. (1) Complete the following chart.
   Subatomic                   Letter Mass Charge
               Mass    Charge
    Particle                  Symbol    Symbol
     Proton    1 amu    +1      p        1 H
                                          1


    Neutron    1 amu    0       n        1
                                             0n


                                e-       0
    Electron   0 amu    -1                   -1e
       Atoms, Ions, and Isotopes
Ex. (2) Rank the subatomic particles from highest
        to lowest mass. ______ > ______ > ______
                          n          p        e-

• An atom’s atomic number (symbolized by the
  letter “Z”) is equal to its number of protons.

• An atom’s mass number (symbolized by the
  letter “A”) is equal to the sum of its number of
  protons and neutrons.

• Caution: mass number is not the same as
  atomic mass, which will be explained later.
      mass number ≠ atomic mass
      Atoms, Ions, and Isotopes
• An ion is a charged atom or group of atoms.

• An ion composed of a single atom is called a
  monoatomic ion.
     Na1+    Cu2+    Al3+   Cl1-   O2-   As3-

• An ion composed of two or more atoms is called
  a polyatomic ion (see Reference Table E).
     NO31-   NH41+    SO42-    H3O1+     PO43-
      Atoms, Ions, and Isotopes
• A positively charged ion (one that has more
  protons than electrons) is called a cation.

     Na1+    Cu2+    Al3+   NH41+    H3O1+

• A negatively charged ion (one that has more
  electrons than protons) is called an anion.
     Cl1-   O2-   As3-   NO31-   SO42-   PO43-

• In a atom, the number of protons is equal to
  the number of electrons.
      Atoms, Ions, and Isotopes
• Dalton proposed, in his atomic theory, that
  atoms of the same element were exactly the
  same.




• Isotopes of the same element exist because not
  all atoms of the same element are completely
  identical.
      Atoms, Ions, and Isotopes
• Isotopes can be defined in several ways that
  actually say the same thing.

  – Isotopes are two atoms of the same element that
    have different masses.

  – Isotopes are two atoms that have the same atomic
    number but that have different mass numbers.

  – Isotopes are two atoms that have the same number
    of protons but different numbers of neutrons.
       Atoms, Ions, and Isotopes
• Isotopes are identified by their isotope
  number which is the same as the mass
  number (the number of protons and neutrons)!

      Hydrogen-1 has 1 proton and 0 neutrons.

      Hydrogen-2 has 1 proton and 1 neutron.

      Carbon-12 has 6 protons and 6 neutrons.

      Carbon-14 has 6 protons and 8 neutrons.
      Atoms, Ions, and Isotopes
                                     20
Ex. (1) K-39: #p = _____ and # n = _____
                     19

Ex. (2) Ni-59: #p = _____ and # n = _____
                     28               31

                     7               7
Ex. (3) N-14: #p = _____ and # n = _____

                         Ba    137
Ex. (4) 56 p and 81 n : _____-_____

                          Si
Ex. (5) 14 p and 15 n : _____-_____
                               29

Ex. (6) 43 p and 56 n : _____-_____
                          Tc   99

				
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posted:10/3/2012
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