Lewis Dot Diagrams and Ions

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Lewis Dot Diagrams and Ions
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Valence Electrons

• The valence electrons are the electrons in the
  outermost shell of the atom
• Consider sodium
• How many protons?
• How many neutrons?
• How many electrons?
• Draw a Bohr model for sodium

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Valence Electrons

• Bohr model for sodium
• The electron(s) in the highest shell are valence
  electrons

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Lewis Dot Diagram

• To draw a Lewis Dot Diagram
• Write the element symbol
• Figure out how many valence electrons the atom
  has
• Use dots to represent the valence electrons
• Put them in pairs around the 4 sides of the
  element symbol
• For example try sodium

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Lewis Structure Practice

• Draw a Lewis Structure for
• Calcium
• Neon
• Silicon

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Ions

• Ions are atoms that have the same number of
  protons, but different numbers of electrons
• An ion forms when an atom gains or loses
  electrons to become more stable
• Which group is the most stable?
• How many valence electrons does that group have?

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Ions

• When nonmetals form ions, they tend to gain
  electrons to fill their valence shell with 8
  electrons
• When metals form ions, they tend to lose all of
  their valence electrons

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Positive Ion Formation

• Atoms in Group 1 lose 1 electron to form ions
  with a 1 charge
• Atoms in Group 2 lose 2 electrons to form ions
  with a 2 charge
• Atoms in Group 13 lose 3 electrons to form ions
  with a 3 charge
• Positive ions are called cations

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Negative Ion Formation

• Atoms in Group 17 gain 1 electron to form ions
  with a -1 charge
• Atoms in Group 16 gain 2 electrons to form ions
  with a -2 charge
• Atoms in Group 15 gain 3 electrons to form ions
  with a -3 charge
• Negative ions are called anions

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Ionic Compounds

• When atoms form ionic compounds, an atom
  transfers one or more of its valence electrons to
  another atom.
• Consider NaCl
• Na loses 1 electron to become Na1
• Cl gains 1 electron to become Cl-1
• The transfer of electrons from one atom to the
  other causes a more stable arrangement of
  electrons.

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Ionic Compounds

• May be made from a metal and a nonmetal - KI
• May be made from a metal and a polyatomic ion
  (Look at your reference table) LiOH
• May be made from two polyatomic ions - NH4C2H3O2

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Naming Ionic Compounds

• The name of the positive ion stays the same
• The end of the element name of the negative ion
  is changed to an ide suffix
• Chlorine to chloride
• Sulfur to sulfide
• Phosphorus to phosphide
• Polyatomic ions stay as they are written

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Ionic Formulas

• What ion does sodium form?
• Na1
• What ion does chlorine form?
• Cl-1
• What do we change the name of the negative ion
  to?
• Chloride
• What is the name of the compound?

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Ionic Formulas

• What is the formula for the compound made from
  sodium and chloride ions?
• What is the compound made from potassium and
  iodide ions?

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Ionic Formulas Activity

• Work in pairs to complete the activity.
• Please put all of the shapes back in the bags
  when you are finished.

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Rules for Naming Ionic Compounds

• The first element keeps its name.
• For monatomic ions, the second element gets the
  ide suffix (ending).
• Polyatomic ions always keep their names whether
  they are first or second.

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Practice

• Name the following ionic compounds
• KF
• MgBr2
• Li2S
• Ca3N2
• NaNO3
• Mg(OH)2

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Exit Ticket

• Draw a Lewis Structure for magnesium
• Give the charge on a magnesium ion
• Give the formula for a compound made from
  magnesium and bromine
• Give the name for CaCl2