Chem chapt' 7 notes

1
Chem chapt. 7 notes chemical bond- link between
atoms Nucleus attracts valance electrons Ionic
bond- where 1 atom gives up e and the other takes
them - TRADING ELECTRONS covalent bond- share e
in the valance level so both have full
shell Bonds can be pure Ionic or Covalent or
somewhere in between (polar covalent), polar
covalent means the electrons are not evenly
shared) nonpolar covalent means even
sharing
2
if you take something from groups 1-2, and bond
to atom from group 16-17, most likely ionic.
if you bond 2 nonmetals, covalent,
closer atoms are together, less polar they are
3
chart pg 242 . have students Put this chart on
their Periodic Table. Just subtract the
electronegativity And match them to the chart on
the next page
4
4
ionic
1.7
polar
.4
nonpolar
0
5
Octet rule- all atoms gain, lose or share
electrons in order to have a full valance
shell. How many valance electrons do atoms start
with? depends on their group- remember group 1
has 1 ( they are a 1s1 or 2s1 or whatever) group
2-12 have 2, group 13 has 3 up to group 18 which
has 8. sometimes it is useful to draw the
valance electrons, in a method called Lewis dot
notation
6
the Lewis dot notation simply shows the valance
electrons as dots around the atoms chemical
symbol. only hint is to put them
top/bottom/left/right, then go back and make
pairs. Na C
Br
7
How an ion is written- Once you know how many
valance e- you have you can decide how many it
would lose or gain. Left half loses, will make
positive ions group one all become 1 ions Na
1 group 2-12 all are 2 ions, Fe2 Group 13
3, Al 3 group 14 C/- 4 Right side gains
e- become negative Group 15 -3, so N-3 GRoup 16
-2 so O -2 and G 17 are -1
8
monatomic ions Na and Cl- Ca 2 and
P-3 or polyatomic ions these are
groups of atoms with a charge SO4 -2 or NO3
-1 still put them into reactions the same way.
still balance charges
9
(No Transcript)
10
covalent compounds How do you know something is
a covalent molecule - it has nonmetals only. H,
C, O, N, S, P and a few times the halogens or
others will get in the game To name them - use
prefixes to tell how many of each are in the
compound prefixes for covalent compouns
mono-1 penta 5 nona-9 di-2 hexa
6 deca-10 tri-3 hepta 7 tetra-4 octa-8
11
Lets try some!!! CO2
carbon dioxide CO carbon monoxide
NO3 nitrogen trioxide N2O3 Dinitroge
n trioxide PCl3 Phosphorus
trichloride H2O Dihydrogen oxide technically
you only use mono with Oxygen when it is with C,
N, or S.
12
Other notes to know about naming hydrates- have
water bound up in the molecule, so we add the
word hydrate to them along with a prefix to tell
how many Copper sulfate pentahydrate CuSO4
5H2O if that same substance has the water removed
it is "anhydrous" MgSO4 7H2O
13
Also there are a whole group of compounds called
acids,which have hydrogen attached to a
molecule mostly these look like ionic compounds
except the positive ion is Hydrogen if it is
binary, like HCl HF H2S Name these by
calling them Hydro ____ ic acid IF with
polyatomic ion, Like H3PO4 or H2SO4 drop the
hydro and just use _____ ic acid there are 2
exceptions- H2SO3 is sulfurous acid and HNO2 is
nitrous acid
e
14
characteristics of ionic and covalent molecules!
ionic crystals covalent molecules
never alone, always in lattice much stronger
molecules always polar, can be solids
liquids or gases metal with non metal polar or
non polar ( O2, CO2) gasoline, oil,
etc organic- made of or makes up
living things all solids brittle crystals
will dissolve in water and in
organic dissolve in water not in
organic substances like gasoline substances condu
ct electricity do not conduct electricity
in and of living things- sugars,
proteins, DNA found in the ground, caves,
geods, diatomic ions in the air found in
parts of gems very high melting points N2
O2 H2 CO2 very low melting points
15
Lets try one! check these statements against
your notes and make a guess about what this is!
white powdery substance dissolves in
water dissolves in rubbing alcohol melts and
burns over bunsen burner doesn't conduct
electricity
16

• Gerometry, and lewis structures.
• Used for covalent compounds, they show all shared
  and unshared electrons
• Give a picture of a covalent compound, and how
  all atoms share electrons to have eight.

17

• Rules to writing
• Count all valance electrons before
• Put one atom in middle. It should be carbon if
  you have it, or whatever atom is single.
• If 3 singles, then choose the one with the lowest
  electronegativity
• Put all other atoms around the central atom (
  like lewis dots) and fill in lines to show bonds
• Now fill in with free electrons, by pairs, till
  all atoms have 8.
• Count valance electrons in picture, they should
  match the count you made in step one
• If they do not match, make double bonds until
  they do.