Transcript Ch 5 Structure of Matter

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Ch 5 Structure of Matter
Bonding, Naming & Writing
Formulas of Compounds
Do You Remember?
• The difference between a mixture
& a compound?
–Which one changes properties
when made?
• Why does it take more energy to
separate a compound?
–Where is energy stored?
Laws of Chemical Combination
1. Law of Definite Proportions – a pure
compound has the same elemental composition
regardless of its source.
Ex. Table salt (sodium chloride) is salt no
matter where or how it was made. It’s always NaCl
2. Law of Multiple Proportions – elements can
combine in different ways to form different
substances.
Ex. Combine C, H, O in different ways to get
different compounds like
C12H22O11 - Sugar
C6H10O5 - Starch
Chemical Formulas
•The subscript tells how many atoms of element in front of it.
•If outside parentheses, the subscript applies to all inside.
•Number 1 isn’t used in formulas; it’s implied.
Compounds – chemical combinations
What atoms and how many of each are in
the formulas below?
• Mg(OH)2 – 1 magnesium, 2 oxygen, 2 hydrogen
• CuSO4
• Pb(NO2)4
• CH4
• Al(NO3)3
Molecular VS Empirical Formulas
A molecular formula shows
the exact number of atoms of
each element in the smallest
unit of a substance
An empirical formula shows
the simplest
whole-number ratio of the
atoms in a substance
molecular
empirical
H2O
H2O
C6H12O6
CH2O
O3
O
N2H4
NH2
Change Molecular to Empirical
Reduce the subscripts to show lowest whole
numbers possible.
• C5H10 5 goes into 5 once; 5 goes into 10 twice  CH2
• C6H8O6
• Hg2F2
• CO2
• N2O4
• C6H14
Molecular Mass – determine the
mass of the entire molecule
• CH4 = 1 C @ 12 amu + 4 H @ 1 amu = 16amu
• H20
• NO2
• C3H8
• CH3OOH
• HBr
Classes of Compounds
• Ionic Compound
– Metal (+ ion) attracted to
nonmetal (– ion)
– Held together by opposite
charges (ionic bonds)
– Smallest: formula unit
• Covalent Compound
– Electrons are shared
(covalent bonds)
– Usually between 2 or more
nonmetals
– Smallest: molecule
Ionic or Covalent?
How can you tell?
Look to see if the elements are metal &
nonmetal (ionic) or just nonmetal (covalent).
• BaCl2 – Barium is metal, Chlorine is nonmetal = Ionic
• H2O – Hydrogen is nonmetal, Oxygen is nonmetal = covalent
• CaO
• Fe2(SO4)3
• CO2
• NH3
• Fr2S
Molecular Models
Metallic Bonding
Metallic bonds occur in metals.
A metal consists of positive ions surrounded
by a “sea” of mobile electrons.
Four Characteristics of a Metallic Bond.
1. Good conductors of heat &
electricity
2. Strong
3. Malleable and Ductile
4. Luster
Network Solids
Which have more attraction between molecules: solids, liquids, or gases?
Covalent Network Solid –
covalently bonded atoms
linked in one big network or
one big macromolecule.
Ionic Network Solid –
+ ion & - ions attracted to each
other
High melting & boiling points – stuck together
Review
N2 (
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