Download Atomic Structure

Atomic Notation
 Atomic Notation represents the number of protons and
neutrons in the nucleus of an atom
 The Atomic Number, Z, represents the number of
protons in the nucleus. It also represents the number of
e- in a neutral atom.
 The Mass Number, A, represents the total number of
protons and neutrons in the nucleus of an atom
Atomic Notation
 Atomic Number is 11
 # of p+ = 22 protons; # e- = 11 electrons
 The Mass number is 23
 #n= 23-11=12 neutrons
Atomic Notation
• Find the
• Number of protons
• Number of neutrons
• Number of electrons
• Atomic number
• Mass number
Atomic Notation
 If an element has an atomic number of
34 and a mass number of 78 what is the
 Number of protons
 Number of neutrons
 Number of electrons
 Complete symbol?
Isotopes
 Atoms of the same element can have
different numbers of neutrons (Dalton was
wrong)
 These atoms of the same element would
have different mass numbers
 These “cousins” of the same element are
called isotopes
 Most elements occur naturally with varying
number of neutrons
Hydrogen Isotopes
 Hydrogen has 3
Isotopes
 1 proton and 0 neutrons,
protium
 1 proton and 1 neutron,
deuterium
 1 proton and 2 neutrons,
tritium (radioactive)
Naming Isotopes
 To name an isotope properly, we put the
mass number after the name of the element
 Carbon-12 (6 protons and 6 neutrons)
 Carbon-14 (6 protons and 8 neutrons)
 Uranium-235 (92 protons and 143
neutrons)
Practice
 Write the symbol for Cobalt-60
 How many protons and neutrons does
an atom of mercury-202 have?
 How many electrons are present in an
atom of Copper-63?
Measuring Atomic Mass
 All of the elements on the Periodic Table have a Mass
Number that is in decimal form, or not a whole
number… why?
• The Mass number
reported on the periodic
table is a “weighted
average” of the isotopes
that are naturally
occurring
Measuring Atomic Mass
 The Mass Number= the Atomic Mass, or Atomic Weight
 The mass of 1 mole of an element (unit 4)
 The number of neutrons and protons present
 The mass of one atom of an element relative to an atom of
another element
 Unit: Atomic Mass Unit (amu)
 The standard for the amu scale is Carbon:
 Carbon= 6p+ and 6n0= mass standard of 12 amu
 All other atoms are designated relative to Carbon. I.e. Hydrogen is
1/12th the mass of carbon (or Atomic Mass 1 amu
Mathematics of Isotopes
 A weighted average means that the numbers of all
the objects are not equal, but occur in different
amounts
 Calculated by multiplying the percent of the
object (as a decimal number) by its mass for
each object and adding the numbers together
Mathematics of Isotopes
 Copper has 2 isotopes:
 Copper-63 with a mass of 62.930 amu and 69.09%
abundance
 Copper-65 with a mass of 64.928 amu and 30.91%
abundance
 62.930 𝑎𝑚𝑢
63.55 𝑎𝑚𝑢
0.6909 + 64.928𝑎𝑚𝑢 0.3091 =
Isotope Examples
 Magnesium has 3 isotopes. 78.99%
Magnesium-24 with a mass of 23.9850amu,
Magnesium-25 with a mass of 24.9858 amu,
and the rest Magnesium-26 with a mass of
25.9826 amu. What is the atomic mass of
Magnesium?
 Boron is 20% B-10 and 80% B-11. What is the
Atomic Mass of Boron?
Ions
 Result from loss or gain of e- by an atom
Ions
𝟑𝟓
−
𝐂𝐥
𝟏𝟕
Ions
 What is the standard atomic notation for the
aluminum atom and ion?