• Come and get your Unit 3 Worksheet
• Atomic structures & Lewis Structures were
marked
• Do corrections on these two sections first
• Option 1: hand in at the end of class and I post
answers
• Option 2: hand in Tuesday and I don’t post
answers
Nuclear Notation
• Middle: element symbol
• Top left: mass number
• Bottom left: atomic number
• Top right: charge
Lewis Structures
• All the molecules we have done have full
octets so make sure atoms are not sharing
more than 8 or less than 8
• Make sure you don’t have more electrons
than the total # of valence electrons
• Formal charge = valence e- - # of bonds - # of
nonbonding e-
Polarity
• Lots of you forgot to label dipole moments!
• Draw all the arrows for all bonds then add
them together
• Dipole moments occur when there is an
electronegativity difference
Atomic Mass
• When using percentages in calculations, you
must always first convert into a decimal!
• Significant figures
Atomic Radius
• Large increase with additional shells (down a
column)
• Increases with atomic #: more protons = more
attraction between nucleus and electrons
• Greater attraction pulls shells in closer so the
atom becomes smaller
Atomic Radius
Ionization Energy
• Energy required to strip off outermost e- of
atom or molecule
• Increases going right and up on the periodic
table
• Noble gases have the highest IE because they
have full valence and are very stable
• Valence e- of smaller elements are closer to
the nucleus so there is stronger attraction
• Fewer e- also means less repulsion & shielding
Ionization Energy
Electronegativity (e- Affinity)
• The attraction of an atom for its electrons
• Small IE = less electronegativity: if an atom is
not attracted to its e- then of course it would
be easier to pluck off
• We will revisit electronegativity when we talk
about bonding polarity
Electronegativity (e- Affinity)
Naming Compounds
• Covalent: use prefixes with “ide” ending
– Mono prefix not needed for 1st atom
– CO2 = carbon dioxide
– CO = carbon monoxide
– H2O = dihydrogen monoxide
• Simple ionic: no prefixes with “ide” ending
• Criss cross to find the charges & subscripts
Naming Compounds
• Do not change the ending of polyatomic ions
to “ide”
– E.g. Na2SO4 = sodium sulfate
• If the 2nd ion is monatomic, still need “ide”
– E.g. NH4Cl = ammonium chloride
Naming Compounds
• Multivalent: metals with >1 charge must be
shown in roman numerals
– E.g. CuSO4 = copper(II) sulfate
– How do we know it’s copper(II)?
• Hydrates: add prefix + “hydrate” at the end
– E.g. CuSO4•6H2O = copper(II) sulfate hexahydrate
Extra Practice
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Corrections for your naming worksheet
Lewis structures: Hebden p.
Key trends: Hebden p.
Polarity: