Atomic Structure

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Atomic Structure

• Introduction to the Chemistry of Life

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ATOMS

• Atoms - the simplest fundamental units of matter
• Atomic Structure
• nucleus
• electron orbitals
• Composed of 3 subatomic particles
• Protons, Neutrons, Electrons

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PROTONS

• PROTONS - subatomic particles found in nucleus of
  the atom
• have a mass of 1.0 Atomic Mass Unit - just call
  it 1.0
• have an electrical charge of 1.0

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NEUTRONS

• NEUTRONS - subatomic particles found in the
  nucleus
• Mass slightly more than 1.0
• Electrical charge of zero - they are neutral
  (hence the name)

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ELECTRONS

• Subatomic particles found in electron shells or
  orbitals outside the nucleus
• Mass is very tiny - just call it zero (0)
• Electrical charge is equal to but opposite in
  sign to the proton or -1.0

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ELECTRONS

• Determine chemical properties of atoms
• Determine reactivity of atoms
• Have potential energy
• Farther away from nucleus, more energy
• Can change energy levels

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ELECTRON

• Atoms typically have zero net charge overall
• Electron Proton
• Sometimes atoms may lose or gain electrons and
  become charged atoms called IONS

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ELECTRONS

• ENERGYof Electrons described with energy shells
  or levels
• 1,2,3,4.....OR K,L,M,N....
• Each energy level has electrons in various
  orbitals
• Two electrons fill an orbital

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ELECTRON Energy Levels

• The first electron shell is full with TWO
  ELECTRONS
• The second shell is full with EIGHT ELECTRONS
• The third shell is full with 18 ELECTRONS (8)

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ELECTRON Energy Levels

• The fourth shell is full with 32 ELECTRONS (2)
• The sequence to remember for the smaller atoms is
  2, 8, 8, 2
• Electrons in the outermost shell are called
  VALENCE ELECTRONS - are reactive

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Reactivity of Atoms

• Determined by / arrgt. of electrons
• Most stable when electrons in lowest energy level
• Closer to full outer level, more stable
  partially full, reactive
• Gain, lose, share electrons to fill outer levels

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PERIODIC TABLE

• The periodic table is an organized listing of all
  known types of atoms with some important
  information for each atom or element

Atomic Mass (weight)
Atomic Number
Chemical symbol
Name of element
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1.0079
12.011
18.998
63.546
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ATOMIC NUMBER

• The atomic number of an atom is simply the number
  of PROTONS found in the nucleus of the atom
• The atomic number of a particular atom or element
  does not change - or if it does you have a
  different type of atom
• Hydrogen for example on the previous slide always
  has one proton in its nucleus

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ATOMIC MASS (WEIGHT)

• The atomic mass of an atom is simply the average
  weight or mass of these particular atoms
• It actually represents the number of PROTONS and
  NEUTRONS found in the nucleus
• For our purposes just ROUND the atomic weight to
  the nearest whole number and then ........

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Atomic wt. -Atomic NEUTRONS

• ATOMIC WT. minus the ATOMIC NUMBER equals the
  number of NEUTRONS in the nucleus

What does the nucleus of hydrogen have in it ?
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ISOTOPES

• ISOTOPES are atoms of the same element which have
  different atomic weights because they have
  different numbers of neutrons.
• For instance
• Carbon has 6 protons, atomic wt 12
• Carbon can also have atomic wt 13
• Carbon also exists with atomic wt 14
• Differences due to number of neutrons, not protons

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THE TEST????

• Be prepared to answer questions about the first
  20 elements
• Examples atomic number, atomic mass, electron
  configurations, valance electrons, etc.

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WHY JUST THE FIRST 20 ?

• Living things are composed of simple, common
  atoms...
• NOT the big, rare fancy atoms ....
• In fact about 95 percent of your body is composed
  of just 6 common atoms ....
• CHNOPS - Remember these!
• CARBON, HYDROGEN, NITROGEN, OXYGEN, PHOSPHORUS
  AND SULFUR

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WHAT DOES HYDROGEN LOOK LIKE ?
E
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HELIUM
Can you draw this Bohr Model ?
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THE BOHR MODEL FOR HELIUM
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LITHIUM
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THE LITHIUM MODEL
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2
4
1
THE FIRST SHELL IS FULL WITH TWO ELECTRONS
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CARBON
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THE CARBON MODEL
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2
6
4
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SODIUM
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THE SODIUM MODEL
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2
1
12
8
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POTASSIUM
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THE POTASSIUM MODEL
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2
8
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8
1
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