Atomic Structure

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• Atomic Structure

3.1
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Atomic History

• In 400 BC a Greek Philosopher named Democritus
  suggested the universe was made of invisible
  units called atoms.

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1800s John Daltons Theory (Still Accepted)

1. Every element is made of tiny, unique particles
   called atoms
2. Atoms of different elements can join to form
   molecules.

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John Daltons Theory- Disproved

1. Atoms are the smallest particles and cannot be
   subdivided.
2. Atoms of the same element are exactly alike in
   mass

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JJ Thomson

• Credited with discovering negative charged
  particles called electrons.

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Rutherford

• Credited with discovering the nucleus.
• Also concluded that atoms are mostly empty space.

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Further Research Finding

• Later on, the discovery of protons and neutrons
  were discovered in the nucleus.
• And it was later concluded that all atoms are
  neutral in charge.
• The number of protons and electrons in any atom
  are always equal.

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Niels Bohr

• Suggested that electrons move around atoms in set
  paths around the nucleus.
• He said each path is an energy level

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Todays Theory

• It has been determined that it is impossible to
  pinpoint an electrons exact position due to its
  tremendous speed.
• Electrons do not move around in definite paths.

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Todays Theory

• Electrons are found in orbitals within energy
  levels. (s, p, d, and f )
• a region in an atom where there is a high
  probability of finding electrons.

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Todays Theory

• Electrons are now viewed as waves vibrating on a
  string rather than simple particles.
• Wave-Particle Duality Theory

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What are atoms?

• The smallest part of an element that still has
  the elements properties.

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Parts of an atom

• Nucleus
• Proton
• Neutron
• Electron

Subatomic particles
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Nucleus

• center of an atom
• positively charged
• makes up 99.9 of the atoms mass
• contains protons and neutrons

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Protons

• Charge ()
• Mass is equal to 1 atomic mass unit (amu)
• Found in the nucleus
• Identifies the element/atom

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Neutrons

• Charge (0) neutral
• Mass is equal to 1amu
• Found in the nucleus
• Helps determine mass

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Electrons

• Charge is negative (-)
• Mass is equal to 0 amu
• Found outside the nucleus, in the electron cloud

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Energy levels

• 1st level holds up to 2 e-
• 2nd level holds up to 8 e-
• 3rd level holds up to 8 or 18 e-
• 4th level holds up to 8, 18, or 32 e-
• Outer Level holds up to 8 e-
• (called valence electrons)

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Valence Electron

• The number of electrons in the outermost electron
  shell.
• Most important

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A Guided Tour of the Periodic Table

• 3.2

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Periodic Law

• Properties of elements tend to change in a
  regular pattern when elements are arranged in
  order of increasing atomic number.

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Periodic Law

• Periodic Table is set up by increasing atomic
  number.
• Atomic Number is the of protons in the atom.

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Average Atomic Mass
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Atomic Number

• tells you number of protons
• Never Changes for an atom.
• Appears as a whole on the periodic table.
• No two elements can have same atomic .

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Atomic Number
Atomic Number
of protons
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Mass Number

• The mass of an atom
• Total number of protons plus neutrons in the
  nucleus of a single atom.
• Atoms of the same element wont always have the
  same mass number

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Mass Number
of neutrons
Mass
of protons
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Isotopes

• Any atoms having the same number of protons but
  different number of neutrons.
• So they also have different mass numbers.

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Average Atomic Mass

• Average mass of all known isotopes for an element
• Found on the periodic table as a number with a
  decimal

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Atoms Charge

• They are neutral.
• All atoms have the same number of protons and
  electrons.
• Charges cancel each other out.

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Ions

• Charged particles.
• Form when atoms lose or gain electrons.
• They do this so the ions have a full outer shell
• Two Types.

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Cations

• Positively charged ions.
• Form when atoms lose electrons.
• Metals
• Left side of table

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Cations

• of protons greater than of electrons
• More () than (-)

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Na Atom
Na Cation
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Anions

• Negatively charged ions.
• Form when atoms gain electrons.
• Nonmetals
• Right side of table

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Anions

• of protons less than of electrons
• More (-) than ()

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Cl- Anion
Cl atom
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Quantifying atoms or ions
1
Protons 3 Neutrons 7-3 4 Electrons
3 Electrons 3 -1 2
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Families of Elements

• 3.3

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Periodic Table

• Periods
• -a horizontal row of elements.
• -Tells you the electrons energy level.

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Periodic Table

• Groups (families)
• -a vertical column of elements.
• -Tells us the of valence electrons and the
  elements chemical properties.

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Types of Elements

1. Metals
2. Nonmetals
3. Semiconductors/metalloids

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Alkali Metals
Nobel Gases
Non Metals
Alkaline Earth Metals
Metalloids
Halogens
Other Metals
Transition Metals
Inner Transition Metals
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Alkali Metals Group 1

• Most reactive metals
• one valence e-
• Found as compounds (salts) and not elements due
  to reactivity.
• As elements they are soft metals and good
  conductors.

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Alkaline-earth Metals Group 2

• Less reactive than Alkali
• They are also more commonly found as compounds
• 2 most common are Ca and Mg.

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Transition Metals Groups 3-12

• Less reactive than groups 1 and 2
• Good conductors

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Transition Metals

• All solids with the exception of mercury
• Valuable metals (Ag, Au, Pt, Cu,
  Ni, Fe, Co)

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Non Metals

• Are not able to conduct electricity or heat very
  well.
• Found in groups 13-18, with the exception of
  hydrogen

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Carbon

• Found as an element (coal, diamond, graphite)
• Found in millions of different compounds
• Called Organic Compounds

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HYDROGEN

• It is a gas/nonmetal
• A very explosive gas.
• It is located in group one because it has one
  valence electron
• http//video.google.com/videoplay?docid-238011814
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Oxygen and Nitrogen

• Oxygen is the most common element found on Earth
• Nitrogen most common gas found in the atmosphere

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Halogens Group 17

• Most reactive nonmetals
• Form salts with group 1
• Used to kill bacteria
• Bromine only liquid nonmetal

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Noble Gases Group 18

• Stable and not reactive. (inert)
• Dont form compounds.
• They have a full valence shell.

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Metalloids (Semiconductors)

• 7 elements on the step
• Properties of both metals and non-metals.
• Silicon the most familiar (computer chips)

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Inner Transition Metals

• Two rows at the bottom
• Some are Radioactive ex. Uranium
• 93 and greater are all manmade

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Moles

• 3.4

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Counting Units

• We buy things by the dozen.
• One dozen 12 items
• We use the unit mole to count things in chemistry

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Moles

• the SI base unit that describes the amount of a
  substance.

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Avogadros Constant

• Represents the number of particles in one mole of
  a substance.
• The number is 6.02 x 1023 particles, atoms, or
  molecules

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Moles

• Used for counting with really tiny atoms
• One mole represents the atomic mass of an
  element.

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Molar Mass

• The mass in grams of 1 mol of a substance.
• Using the periodic chart you can determine the
  molar mass of any element or compound.

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Molar Mass Example

• So how many grams in two moles of Ca?

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Solution

• The molar mass of Ca is 40 g/mol.
• 2 moles x 40 grams 80 g
• 1 mole

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Mole Problems

• You can determine how many moles of a substance
  you have if you know the mass of the substance.

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Example Problem

• If you have 92 grams of Na how many moles would
  you have?

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Solution

• MM of Na is 23 g/mole
• 92 g x 1 mole 4.0 moles
• 23 g