Properties of Elements

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Properties of Elements
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Atomic Radius

• A measure of the size on an atom.
• What determines an atoms size?
• Remember, the nucleus is very very small and
  compact. It is the electrons that determine how
  big the atom is.

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Atomic Radius

• It is hard to measure where the moving e- are at
  any moment, so they can not be easily used to
  measure size.
• DEFINITION Half the distance between the nuclei
  of two adjacent atoms in a crystal

½ distance
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Ionization Energy

• DEFINITION The amount of energy it takes to
  remove the outermost e- from a neutral atom in
  the gas phase
• X Ionization energy X
  e-

Neutral atom
Cation electron
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Electronegativity

• DEFINITION A measure of the attraction an atom
  has for electrons when it is bonded to another
  atom.
• Scale is from 0.7 (low, Cs) to 4.0 (high, F)

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Trends in Atomic Radius

• Across a period radius decreases because there
  are more protons in each successive atoms
  nucleus, pulling harder on the e- and making the
  atom smaller
• Down a group radius increases because the
  atoms have more energy levels farther from the
  nucleus, making the atom bigger

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Trends in Ionization Energy

• Across a period I.E. increases because there
  are more protons in each successive atoms
  nucleus, pulling harder on the e- and making it
  harder to remove the e-
• Down a group I.E. decreases because the atoms
  have more energy levels farther from the nucleus,
  so the outer e- are less attracted to the nucleus
  and are therefore easier to remove. Also, inner
  e- shield the outer e- from the pull of the
  nucleus.

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Trends in Electronegativity

• Across a period Electronegativity increases
  because there are more protons in each successive
  atoms nucleus, pulling harder on the e-
• Down a group Electronegativity decreases
  because the atoms have more energy levels farther
  from the nucleus, so the nucleus has less
  positive pull on the e-. Also, inner e- shield
  the outer e- from the pull of the nucleus

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Ionic Radius

• If an atom GAINS e-, it gets bigger in size
• So.negative ions (anions) are bigger than
  their neutral atom

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Ionic Radius

• If an atom LOSES e-, it gets smaller in size
• So positive ions (cations) are smaller than
  their neutral atom

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Group 1 alkali metals

• Electron configuration ends with S1
• Lose this outermost e- easily (low Ionization
  energy and electronegativity) forming 1 cations
• VERY reactive! Francium is MOST reactive
• Not found uncombined in nature
• Form stable compounds with non metals like NaCl

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Group 2 alkaline earth metals

• Electron configuration ends with S2
• Lose these 2 outermost e- easily (low Ionization
  energy and electronegativity) but not as easily
  as Group 1 metals losing only 1 e-
• Form 2 cations
• Reactive! (but not as much as Group 1)
• Not found uncombined in nature
• Form stable compounds with non metals like MgCl2

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Groups 3-12 transition metals

• Highest energy level ends with S2
• but d-orbitals are being filled
• Tend to lose the S2 e- easily, forming 2
  cations, but many can also form 1 or 3
  (multiple oxidation states)
• Less reactive than Groups 1 or 2
• Form colorful ions and compounds

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Groups 13

• Electron configuration ends with S2P1
• Lose the three S2P1 e-, forming 3 cations
• Both metalloids and metals in this group

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Groups 14

• Electron configuration ends with S2P2
• Dont tend to form ions
• Non metals, metalloids and metals in this group

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Groups 15

• Electron configuration ends with S2P3
• Tend to gain 3 e-, forming -3 anions
• Non metals, metalloids and metals in this group

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Groups 16

• Electron configuration ends with S2P4
• Tend to gain 3 e-, forming -2 anions
• Non metals, and metalloids in this group
• Reactive! Tend to form stable compounds with
  metals like MgO

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Groups 17 Halogens

• Electron configuration ends with S2P5
• Tend to gain one e-, forming -1 anions. Very
  high electronegativity and ionization energy. (F
  is highest electronegativity with 4.0)
• Non metals only in this group
• Only group to have all three phases of matter at
  room temperature (s, l, g)
• VERY Reactive! Not found uncombined in nature.
  Tend to form stable compounds with metals like
  NaCl. Most reactive is F.

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Groups 18 Noble gases

• Electron configuration ends with S2P6
• Energy level is full
• Do not lose or gain e-. Do not form ions.
• UNreactive! Not found combined with other
  elements in nature. Do not form compounds.