Structure of the Atom

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Structure of the Atom
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SC Standards Covered

• Standard PS-2.1 Compare the subatomic particles
  (protons, neutrons, electrons) of an atom with
  regard to mass, location, and charge, and explain
  how these particles affect the properties of an
  atom (including identity, mass, volume, and
  reactivity).
• Standard PS-2.4 Use the atomic number and the
  mass number to calculate the number of protons,
  neutrons, and/or electrons for a given isotope of
  an element.

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Scientific Shorthand

• Each element can be represented by a one, two,
  or three letter chemical symbol
• Each symbol consists of one capital letter plus
  one or two lower case letters

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Atomic Components
Atom - smallest particle of an element which
retains the properties of that element.
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Atomic Theory

• Atoms are building blocks of elements
• Similar atoms in each element
• Different from atoms of other elements
• Two or more different atoms bond in simple ratios
  to form compounds

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Basic Structure

• The center of the atom is called the nucleus.
• Surrounding the nucleus is the electron cloud.

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Subatomic Particles
Particle Symbol Location Charge Mass
Electron
Space around the nucleus
1/1840 amu
e-1
-1
In the nucleus
Proton
1
p1
1 amu
In the nucleus
0
1 amu
Neutron
n0
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Quarks

• Quarks particles that make up protons and
  neutrons
• Three quarks make up a proton or neutron

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Fine Points to the Structure of the Atom

• All of the mass of an atom is located in the
  nucleus
• All of the volume of the atom is taken up by the
  electron cloud

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Atomic Number
Atomic number counts the number of protons in
an atom
- Used to identify the element - Periodic Table
arranged by it
Atoms are electrically neutral (not charged)
of protons of electrons
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Learning Check

• State the number of protons for atoms of each
  of the following
• A. Nitrogen
• 1) 5 protons 2) 7 protons 3) 14
  protons
• B. Sulfur
• 1) 32 protons 2) 16 protons 3) 6
  protons
• C. Barium
• 1) 137 protons 2) 81 protons 3) 56
  protons

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Solution

• State the number of protons for atoms of each of
  the following
• A. Nitrogen
• 2) 7 protons
• B. Sulfur
• 2) 16 protons
• C. Barium
• 3) 56 protons

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Mass Number

• Mass Number Counts the number of protons and
  neutrons in an atom
• Number of Neutrons
• Mass Number Proton Number (atomic )

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What is the Mass Number of the following Atoms?
1
12
238
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Isotopes
Isotopes - atoms of the same element with
different numbers of neutrons
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More Examples of Isotopes
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Notation of Isotopes
Potassium - 40
Mass number
40
K
19
Atomic number
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Learning Check

• Naturally occurring carbon consists of three
  isotopes, 12C, 13C, and 14C. State the number of
  protons, neutrons, and electrons in each of these
  carbon atoms.
• 12C 13C 14C
• 6 6
  6
• P _______ _______
  _______
• N _______ _______
  _______
• E _______ _______
  _______

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Carbon - 12
Carbon - 13
Carbon - 14
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• Atomic mass - weighted average of all the
  isotopes of a particular element
• This is the mass indicated on the periodic table.
• This number will be closest to the most common
  isotope of the element.

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Learning Check

• An atom of zinc has a mass number of 65.
• A. Number of protons in the zinc atom
• 1) 30 2) 35 3) 65
• B. Number of neutrons in the zinc atom
• 1) 30 2) 35 3) 65
• C. What is the mass number of a zinc isotope
• with 37 neutrons?
• 1) 37 2) 65 3) 67

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Solution

• An atom of zinc has a mass number of 65.
• A. Number of protons in the zinc atom
• 1) 30
• B. Number of neutrons in the zinc atom
• 2) 35
• C. What is the mass number of a zinc isotope
• with 37 neutrons?
• 3) 67

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Learning Check

• Write the isotope (nuclear) notation for atoms
  with the following
• A. 8 p, 8 n, 8 e- ___________
• B. 17p, 20n, 17e- ___________
• C. 47p, 60 n, 47 e- ___________

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Solution

• 16O
• A. 8 p, 8 n, 8 e- 8
• B. 17p, 20n, 17e- 37Cl
• 17
• C. 47p, 60 n, 47 e- 107Ag
• 47