Ch 7 PowerPoint Notes

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Ch 7 PowerPoint Notes
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Section 7.1 - Ions

• OBJECTIVES
• Determine the number of valence electrons in an
  atom of a representative element.

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Section 7.1 - Ions

• OBJECTIVES
• Explain how the octet rule applies to atoms of
  metallic and nonmetallic elements.

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Section 7.1 - Ions

• OBJECTIVES
• Describe how cations and anions form.

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Why do some elements react to form compounds and
others do not?Is there any way to predict if
atoms might react with each other?Is there any
way to predict what chemical formulas might be
formed?
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Ionic and Metallic Bonding
Na 1, Na 1 or Na cation , missing 1
e- O2- anion, gained 2 e- (the number is the
charge on ion, not of e- gained or lost,, i.e.,
1 means 1 electron lost, not 1 gained.)
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Ion definitions

• Valence electrons Outermost electrons. The s
  and p electrons in the outer energy level. The
  highest occupied energy level.
• Core electrons are those in the energy levels
  below.
• Ion An atom that has lost or gained an
  electron. Ions have a or - charge.
• (Atoms are always neutral, of p of e-)
• Cation Positive Ion or metals, gained e-.
• Anion Negative Ion or non-metals, Lost e-.

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Valence Electrons are?

• The electrons responsible for the chemical
  properties of atoms, and are those in the outer
  energy level.
• Valence electrons - The s and p electrons in the
  outer energy level
• the highest occupied energy level
• Core electrons are those in the energy levels
  below.

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Keeping Track of Electrons

• Atoms in the same column (group)...
• Have the same outer electron configuration.
• Have the same valence electrons.
• The number of valence electrons are easily
  determined. It is the group number for
  representative.
• Group 2A Be, Mg, Ca, etc.
• have 2 valence electrons
• Group 8A, Noble gases has 8.

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Electron Dot diagrams are

• DEF Shows the 8 valence electrons as dot pairs
  around the chemical symbol.
• A way of showing keeping track
• of valence electrons.
• How to write them?
• Write the symbol - it represents the nucleus and
  inner (core) electrons
• Put one dot for each valence electron (8 maximum)
• They dont pair up until they have to (Hunds
  rule). Do 4 singles before pairs.

X
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Electron Dot diagramsSingle dots can be on any
side.
1A
2A
3A
4A
5A
7A
6A
8A
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Valence e- highest electron energy level of an
atom (ns npwhere n is the same number)Nitrogen
1s2 2s2 2p3 5 Valence e-
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e- dot structures show only valence e-(single
per side/then pair up)2 dots Mg Ne3s2 3p0
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Need to Memorize!! EASY!
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valence e- determine the chemical properties of
an element Alkali metals (1 ve-) - ns1 np0
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Remember s, p, d, f blocks
S
p
1S1 1S2 2S1 2S2 3S1 3S2
1 2 3 4 5 6 7
1 2 3 4 5 6 7
2p1 2p2 2p32p4 2p5 2p6
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Write the e dot structures O 1s2 2s2
2p4  Ne  Na
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Write the e dot structures O 1s2 2s2
2p4  Ne 1s2 2s2 2p6  Na 1s2 2s2 2p6
3s1 3p
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e dot structures show valence e- as dots O
1s2 2s2 2p4  Ne 1s2 2s2 2p6  Na 1s2
2s2 2p6 3s1 3p
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octet rule ions tend to have pseudo noble gas
configuration (8 valence e-)full s and p
orbitals
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Formation of Cations

• Metals lose electrons to attain a noble gas
  configuration.
• They make positive ions (cations)
• If we look at the electron configuration, it
  makes sense to lose electrons
• Na 1s22s22p63s1 1 valence electron
• Na1 1s22s22p6 This is a noble gas
  configuration with 8 electrons in the outer level.

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Electron Dots For Cations

• Metals will have few valence electrons (usually 3
  or less) calcium has only 2 valence electrons

Ca
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Electron Dots For Cations

• Metals will have few valence electrons
• Metals will lose the valence electrons

Ca
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Electron Dots For Cations

• Metals will have few valence electrons
• Metals will lose the valence electrons
• Forming positive ions

Ca2
This is named the calcium ion.
NO DOTS are now shown for the cation.
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Electron Configurations Anions

• Nonmetals gain electrons to attain noble gas
  configuration.
• They make negative ions (anions)
• S 1s22s22p63s23p4 6 valence electrons
• S2- 1s22s22p63s23p6 noble gas
  configuration.
• Halide ions are ions from chlorine or other
  halogens that gain electrons

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Electron Dots For Anions

• Nonmetals will have many valence electrons
  (usually 5 or more)
• They will gain electrons to fill outer shell.

3-
P
(This is called the phosphide ion, and should
show dots)
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Stable Electron Configurations

• All atoms react to try and achieve a noble gas
  configuration.
• Noble gases have 2 s and 6 p electrons.
• 8 valence electrons already stable!
• This is the octet rule (8 in the outer level is
  particularly stable).

Ar
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ATOMNa 1s2 2s2 2p6 3s1 3p0 IONNa1
1s2 2s2 2p6
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a. What is the charge of an e-?b. What is the
e- config for N 3- ion? c. How many e- does
(B) have?d. how many valence e- does (B) have?
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  Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table   Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table   Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table   Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table   Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table   Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table   Common IONIC CHARGES OF REPRESENTATIVE ELEMENTS Add to periodic table
1 1 2 2 13 3 14 15 -3 16 -2 17 -1
Li Na K Rb Cs Be Mg Ca Sr Ba     Al N P As O S Se F Cl Br I
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Why dont the noble gases form ions?
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When writing S2-, what does the 2-
indicate?Does this ion have more or less e
than the original atom?
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Section 7.2 Ionic Bonds and Ionic Compounds

• OBJECTIVES
• Explain the electrical charge of an ionic
  compound.

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Section 7.2 Ionic Bonds and Ionic Compounds

• OBJECTIVES
• Describe three properties of ionic compounds.

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Ionic Compounds compounds formed from cations
and anions Usually a metal and a nonmetal (the
charges always cancel)Na, Cl- NaCl
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Ionic Bonding

• Anions and cations are held together by opposite
  charges ( and -)
• Ionic compounds are called salts.
• Simplest ratio of elements in an ionic compound
  is called the formula unit.
• The bond is formed through the transfer of
  electrons (lose and gain)
• Electrons are transferred to achieve noble gas
  configuration (Octet Rule).

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Ionic Compounds

1. Also called SALTS
2. Made from a CATION with an ANION (or literally
   from a metal combining with a nonmetal)

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Ionic Bonding
Na
Cl
The metal (sodium) tends to lose its one electron
from the outer level. The nonmetal (chlorine)
needs to gain one more to fill its outer level,
and will accept the one electron that sodium is
going to lose.
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Ionic Bonding
Na
Cl -
Note Remember that NO DOTS are now shown for the
cation!
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Chemical formula number of atoms in a formula
unit of an ionic compound (and not the charges
on the ions)Formula unit NaCl
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Ionic Bonding
Lets do an example by combining calcium and
phosphorus
Ca
P

• All the electrons must be accounted for, and each
  atom will have a noble gas configuration (which
  is stable).

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Ionic Bonding
Ca
P
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Ionic Bonding
Ca2
P
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Ionic Bonding
Ca2
P
Ca
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Ionic Bonding
Ca2
P 3-
Ca
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Ionic Bonding
Ca2
P 3-
Ca
P
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Ionic Bonding
Ca2
P 3-
Ca2
P
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Ionic Bonding
Ca
Ca2
P 3-
Ca2
P
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Ionic Bonding
Ca
Ca2
P 3-
Ca2
P
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Ionic Bonding
Ca2
Ca2
P 3-
Ca2
P 3-
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Ionic Bonding
Ca3P2
Formula Unit
This is a chemical formula, which shows the kinds
and numbers of atoms in the smallest
representative particle of the substance. For an
ionic compound, the smallest representative
particle is called a Formula Unit
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Chemical formula number of atoms in a formula
unit of an ionic compound (and not the charges
on the ions)Formula unit NaCl
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Ionic compounds are usually brittle solids at
room temperature, with repeating internal 3-D
crystal patterns, that have high melting points
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Ionic bonds electrostatic force that holds
compound together
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What number of each ion do you need to make an
ionic compound?Na, FNa, SAl, N
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What number of each ion do you need to make an
ionic compound?Na, F NaF Na,
S Na2S Al, N AlN
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Metal bonds valence electrons of metal atoms
can be modeled as a sea of electrons Metallic
bonds free-floating valence electrons attracted
to the positively charged metal ions
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Alloys are mixtures composed of two or more
elements, at leastone of which is a metal
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Quick review questions

• Can have everyone stand up and answers following
  qs to sit down.

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An ionic compound is usually formed between a
metal and a __?
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How many dots around a sodium atom?
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How many dots around a sodium atom?
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What is the charge on a sodium atom?
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What is the charge on a sodium ion?
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What are some ionic compounds formed with sodium?
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What is the charge on an aluminum ion?
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What are some ionic compounds formed with
Aluminum?
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