Unit4: The Structure of Matter

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Unit4The Structure of Matter

• By Ms. Buroker

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Compounds and Molecules

• What are compounds?
• compounds are combinations of elements- these
  elements take on properties in combination that
  are different than when they are alone.

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Compounds

• What makes a compound different than a mixture?
• Remember- mixtures can be physically separated
  because their parts remain chemically unchanged!

Chemical Bonds
The attractive force that holds atoms or ions
together in compounds
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Compounds

• What does the chemical formula tell you about
  the compound?
• CO2 NaHCO3
• 1.) The formula tells you the type of atom that
  is there.
• 2.) The subscript tells you how many atoms are
  there.

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Lets STOP here!

• List the elements in the following compounds and
  how many of each element are in the compounds
• 1.) MgBr2
• 2.) N2O
• 3.)H2O2
• 4.)C9H8O4

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Compounds

• Does the compound tell you how much of the
  substance is there?

NO!!!!!!!!!!!!!!!! What the compound does tell
you is the relationship between the atoms and the
ratio they exist in ALWAYS!
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Compounds

• Does the compounds formula tell you how the
  atoms are connected?

NO- you need the chemical structure to know how
the atoms are connected to one another!
Space- filling model
Ball- and- stick model
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Structure

• How does structure affect properties of
  compounds?

Lets think about the activity, which substance
melted first? NaCl Sugar (C12H11O12) Baking Soda
(NaHCO3)
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Structure

• The structure of matter can determine many
  things about the substance its melting point,
  its boiling point, if its a liquid, gas, or
  solid, etc.

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Chemical Bonds

• Attraction between two or more atoms
• Interaction between valence electrons
• Ionic bonds
• Covalent bonds
• Metallic bonds

Play Game
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The Octet Rule

• This rule states that in order for atoms to feel
  stable, they need 8 electrons in their outer
  shell they need 8 valence electrons.

Yeah Im a happy atom!!
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Okay, so how do we get happy then

• The reason behind why elements bond at all is in
  an effort to gain stability- think the octet
  rule!
• Elements will either gain, lose, or share
  electrons in an effort to get 8 electrons in
  their valance shell!

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Ions

• Elements will either gain, lose, or share
  electrons in an effort to get 8 electrons in
  their valance shell!
• When they lose or gain electrons ions!

The positive charge from the protons and the
negative charge from the electrons are now out of
balance!
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Lets do a little math!
5 5 5 - 4 5 6
So when the protons and electrons are equal the
charge is 0!!!
p
e
0
So when the protons outnumber the electrons by
one, there is an abundance of positive charge
overall, the charge of the atom is 1!!
p
e
1
So when the electrons outnumber the protons by
one, there is an abundance of negative charge
overall, the charge of the atom is -1!!
p
e
-1
The Charge of the ion comes from where there is
an abundance of charge either negative from
there being more electrons or positive from their
being more protons.
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Ionic Compounds

• Exist between metals and non metals
• Attraction exists between ions and - ions
• Electrons go from metals to nonmetals
• electron transfer
• metal nonmetal ion ion
• Electrons lost Electrons gain

Opposite charges attract one another. Metals
are losers they lose electrons so what will
their charge be? Nonmetals gain they pick up
electrons so what will their charge be?
metals make cations when they lose
electrons (metals are losers) non-metals make
anions when they gain electrons
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Lets take a look at some examples

• We can predict how many electrons a metal will
  lose by knowing how many valence electrons it has
  
• We can predict how many electrons a nonmetal
  will gain by knowing how many valence electrons
  it has

Ca has 2 valence e- so it wants to lose those
2e- 20 18 2 (overall charge of the ion)
p
e
Cl has 7 valence e- so it wants to gain 1 more
e- to have 8 total in its valence shell 17 18
-1 (overall charge of the ion)
e
p
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What Charge Will The Ion Have?
1 A
5 A
1
- 3
6 A
2 A
- 2
2
7 A
3 A
- 1
3
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Ionic Compounds

• Ionic compounds are solids at room
  temperature- they are brittle
• They generally have very high melting points
  and boiling points
• They can conduct electricity when dissolved in
  water (electrolytes)

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Ionic Compounds Forming Electrolytes
Ionic compounds form in networks of ions these
ions can break apart in solutions!
Lets Watch a little video to re-cap!
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The Periodic Table Tells Us How Much the Element
wants to HOLD ON to its electrons

• This is called ELECTRONEGATIVITY
• The more ELECTRONEGATIVE the element, the more it
  is greedy with its electrons.
• Electronegative elements REALLY like to keep hold
  of their electrons

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Its like a tug of war for the electrons!!!
The more electronegative element is stronger
and will succeed in pulling the electrons toward
itself!
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Covalent Compounds

• Formed between nonmetals in 4A, 5A, 6A, and 7A
• Electrons are shared between atoms- this is what
  holds them together

So instead of electrons being lost and gained
as in ionic compounds- electrons are simply
shared. This makes for a generally weaker bond!
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Covalent Compounds

• Co means together, so when valence electrons
  are SHARED, this means that the bond is covalent
  they are sharing their electrons together!
• Covalent is the opposite of ionic

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Covalent Compounds

• Molecules are substance that contain only
  covalent bonds!
• These compounds melt and boil at lower
  temperatures than ionic compounds.
• They do not conduct electricity because there
  are no ions involved!

Lets watch a little video!
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Metallic Bonds

• Metallic bonds take place between metals- for
  instance, in a sample of copper wire.

The nuclei of metals are positive and attracted
to the electrons of the other atoms this
overlapping of orbitals is a very strong!!
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Metallic Bonds
Metallic Bonding Animation