• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/67

Click to flip

67 Cards in this Set

  • Front
  • Back
Covalent Compounds
most compounds we come in contact with in our lives are covalent compounds
covalent bonds
result from the sharing of electrons between two atoms
molecule
is a discrete group of atom,s held together by covalent bonds
H2
is a covalent bond the is very stale because it gives the two hydrogen two proton and two electrons which are stable like He which is a noble gas
A solid line between element symbols to represent a two-electron bond
H2
H : H
H-H
Diatomic molecule
contain just two elements in addition to hydrogen there are six others N2 O2 F2 Cl2 Br2 and I2 that are elements only
HF is
also a diatomic molecule
H has one electron F has seven electrons however the combination shares two electrons but leaves three unshared pairs
Unshared pairs of electrons are called
nonbounded electron pairs or lone pairs
In covalent bonding
atoms share electrons to attain the electronic configuration of the noble gas closest to them in the periodic table
for a group of elements to be especially stable they must
process an octet of electrons in their outer shell
Covalent bonds forms when
two nonmetals combine or when a metalliod bonds to a nonmetal
covalent bonding
is preferred with elements in the middle of the periodic table
Lewis structure
electron-dot structures for molecules ---show the location of all valence electrons in a molecule both shared in bonds and unshared
atoms with one, two, or three valence electrons generally
form one,two, or three bonds
atoms with four or more valence electrons form
enough bonds to give an octet, thus, for atoms with four or more valence electrons ----predicted number of bonds = 8 number of valence electrons
a molecular formula shows
the number and identity of all of the atoms in a compound
a Lewis structure in contrast, shows
the connectivity between the atoms, as well as where all the bonding and nonbonding valence electrons reside
3 rules to drawing Lewis Structures
Draw only the valence electrons
give every maingroup element (except hydrogen) an octet of electrons
give Hydrogen two electrons
Multiple bonds
we must convert two lone pairs to two bonding pairs of electrons and form a triple bond
a triple bond
contains six electrons in three two-electron bonds
A double bond contains
four electrons in a two-electron bonds
after placing all electrons in bonds and lone pairs
to form multiple bond if an atom does not have an octet
exceptions to the octet rule
Hydrogen is the notable exception because it accommodates only two electrons in bonding--also Boron in group 3A and elements in the third row and later in the periodic table particularly phosphorous and sulfur
Elements below the third row have
empty d orbitals--PCL and H2S follow the octet rule but H2SO4 sulfuric acid and H3PO4 phosphoric acid have 12 and 10 electrons respectively
Lewis Structures for ions that contain covalent bonds--that is polyatomic ions
we must take the charge into account
Add one electron for each negative charge.
Subtract one electron for each positive charge.
Resonace structures are
Lewis structures having the same arrangement of atoms but a different arrangement of electrons
Two resonance structures differ
in the location of multiple bonds and the position of lone pairs
Neither resonance structure is
an accurate representation of the molecule. it is called a hybrid
Resonance
stabilizes the molecule
We say a molecule or ion that has two or more resonances structures is
resonance-stabilized
Ozone
O3 it protects the earth from ultraviolet light a decrease in ozone would mean an increase in skin cancer and eye cataracts
Naming Covalent compounds
h2o is water
NH3 is ammonia however other covalent compounds with two elements are named to indicate and identify the number of elements they contain
NO2
name the first nonmetal by is element name and the second using the suffix -ide
Add prefixes to show the number of atoms in each element
Nitrogen dioxide
N2O4
dinitrogentetroxide
1
2
3
4
5
mono
di
Tri
Tetra
penta
6
7
8
9
10
hexa
hepta
octa
nona
deca
Molecular structure
Lewis structure does not determine shape but how connected--- H2O is it bent or straight
A group is either an atom or a lone
pair of electrons
Valence shell electron repulsion theory or VSEPR
VSEPR is based on the fact that electrons pairs repel each other
The most stable arrangement keeps these groups as far away from each other as possible
An atom surrounded by two groups is
linear and has a bond angle of 180 degrees
an atom surrounded by three groups is
trigonal planar and has bond angles of 120 degrees
an atom surrounded by four groups is
has bond angles of 109.5 degrees and is called tetrahedral
Any atom surrounded by two groups is
linear and has a bond angle of 180 degrees--ignore multiple bonds in predicting geometry. Count only atoms and lone pairs
Any atom surrounded by three groups is
trigonal planar and has bonds angles of 120 degrees
Any atom surrounded by four groups is
tetrahedral and has bond angles of approximately 109.5 degrees
Drawing a tetrahedral
a solid line is used for bonds in the plane
a wedge for a bond in front of the plane
a dashed line is used for the bond behind the plane
NH3 ammonia
is drawn as a trigonal pyramid
..
H-N-H
I
H
H2O is bent
..
H-O-H
..
A group can also be lone pair
of electrons
Electronegativity
is a measure of an atom's attraction for electron in a bond.
tells us how much a particular atom wants electrons
Electronegetivity
increases across a row of the periodic table as the nuclear charge increases (excluding the noble gases)
Electronegetivity
decreases down a column of the periodic table as the atomic radius increases, pushing the valence electrons farther from the nucleus
Ectronegegativity values are used as a guideline to indicate whether the electrons in a bond are
equally shared or unequally shared between two atoms
When two electrons are equally shared the bond is
non-polar thus Carbon-carbon bonds is nonpolar The same is true whenever two atoms having similar electronegativity are bonded together like C-H is also considered non-polar
Bonding between atoms of different electronegativity results in the
unequal sharing of sharing of electrons for example, in a C-o bond the electrons are pulled away fro C towards the element of higher electronegativity O the bond is polar
The symbol
is given to the less electronegative atom
The Symbol
is given to the more electronegative atom
Electronegativity Difference
Less than 0.5 units
0.5 - 1.9
1.9 and greater
Bond type Electron sharing
nonpolar equally shared
polar covalent unequally shared
electrons are transfered from less electronegative to more
Dipole
the bond is polar or polar covalent it is a dipole that is aseperation of charge
A molecule with no polar bonds is a
nonpolar molecule
a molecule with one polar bond is a
polar molecule
if the individual bond dipoles do not cancel
the molecule is polar
if the individual bond dipoles cancel
the molecule is nonpolar
a molecule with one polar bond is a
polar molecule
if the individual bond dipoles do not cancel
the molecule is polar
if the individual bond dipoles cancel
the molecule is nonpolar
Identify all polar bonds based on negativity differences
Determine the shape around individual atoms by counting groups
decide if individual dipoles cancel or reinforce
list