Ions

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Ions
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Ions And Ionic Compounds

• When an atom or molecule loses electrons, it
  becomes positively charged.
• For example, when Na loses an electron it becomes
  Na.
• Positively charged ions are called cations.

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Ions And Ionic Compounds

• When an atom or molecule gains electrons, it
  becomes negatively charged.
• For example when Cl gains an electron it becomes
  Cl-.
• Negatively charged ions are called anions.
• An atom or molecule can lose more than one
  electron.
• When molecules loose electrons, polyatomic ions
  are formed.

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Ions

• Cation A positive ion
• Mg2, NH4
• Anion A negative ion
• Cl-, SO42-
• Ionic Bonding Force of attraction between
  oppositely charged ions.
• Note SO42- NH4 are polyatomic ions (more
  than 1 element)

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Keeping Track of Electrons

• Atoms in the same column have the same properties
  because
• Have the same outer electron configuration.
• Have the same valence electrons.
• Found by looking up the group number on the
  periodic table.
• The electrons responsible for the chemical
  properties of atoms are those in the outer energy
  level.

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Inner shell holds only 2
Outer Shell 8
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Be
Name the element. Number of shells ? Valence
electrons ?
Beryllium
2nd Period 2 shells
2nd Group 2 valence electrons
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Predicting Ionic Charges
Group 1
Lose 1 electron to form 1 ions
H
Li
Na
K
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Predicting Ionic Charges
Group 2
Loses 2 electrons to form 2 ions
Be2
Mg2
Ca2
Ba2
Sr2
10
Predicting Ionic Charges
Group 13
Loses 3 electrons to form 3 ions
B3
Al3
Ga3
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Predicting Ionic Charges
Group 14
Lose 4 electrons or gain 4
electrons?
Neither! Group 13 elements rarely form ions.
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Predicting Ionic Charges
Nitride
N3-
Group 15
Gains 3 electrons to form 3- ions
P3-
Phosphide
As3-
Arsenide
13
Predicting Ionic Charges
Oxide
O2-
Gains 2 electrons to form 2- ions
Group 16
S2-
Sulfide
Se2-
Selenide
14
Predicting Ionic Charges
F1-
Br1-
Fluoride
Bromide
Group 17
Gains 1 electron to form 1- ions
Cl1-
Chloride
I1-
Iodide
15
Predicting Ionic Charges
Group 18
Stable Noble gases do not form ions!