lewis dot structures
how do you find the # of valence electrons for any molecule?
What is the exception? What atom's group number does not equal # of valence electrons?
You look through the periodic table, and look at what group that the molecule is in.
Ex. Oxygen is in group 16, so it has 6 valence electrons.
The exception is helium, which has 2 valence electrons.
1.What do you do if you have too many or too little electrons?
2. What can you not forget when drawing lewis dot structures for elements with a charge?
1. You make a double or triple bond.
2. When drawing Lewis dot structures for elements with a charge, you can not forget the brackets around the structure with the charge at the top.
When would you draw a trigonal planar?
what is the degree?
What structure does it look like?
you would draw a trigonal planar when the central atom is bonded 3 TIMES, with NO LONE pairs.
THE DEGREE IS 120
Trigonal planar looks like bent 1, (2 times, 1 lone pair) but with an atom on top.
how do you find if partial dipoles are present?
what does it have to be between?
find the difference in electronegative of atoms
( use periodic table.)
it has to be between 0.5- 1.67
if a delta positive is surrounded by delta negatives then __________________
if a delta positive is surrounded by delta negatives then ___ it has no dipole, and it cancels out___
Fill in the blank (when drawing lewis dot structures)
1. For molecules with only 2 elements ___________________
2. For molecules with more than 2 elements, find the __________ (least electronegative atom), write the remaining atoms _____________________
1. For molecules with only 2 elements, arrange the atoms symmetrically
2. For molecules with more than 2 elements, find the _central atom__ (least electronegative atom), write the remaining atoms _in the order that they appear in the formula
What does a single bond look like?
A double bond?
A triple bond?
1. One line between atoms
2. Two lines between atoms
3. Three lines between atoms.
WHEN WOULD YOU DRAW A TRIGONAL PYRAMID?
WHATS THE DEGREE FOR A TRIGONAL PYRAMID?
What structure does a trigonal pyramid look like?
You would draw a trigonal pyramid when the central atom is bonded 3 TIMES, WITH ONE LONE PAIR. THE DEGREE IS LESS THAN 109.5 DEGREES.
The trigonal pyramid looks like a tetrahedral without the top atom.
(it's angle is less than 109.5 degrees while a tetrahedrals is exactly 109.5)
the molecule with the HIGHER e-neg will get the ___________ sign.
The molecule with the lower e-neg will get the _________ sign.
the molecule with the HIGHER e-neg will get the ____delta negative______ sign.
The molecule with the lower e-neg will get the __delta positive_______ sign.
hydrogen bonding only occurs in _________ molecules, and hydrogen is bonded to _______(three elements)
hydrogen bonding only occurs in __polar_______ molecules, and hydrogen is bonded to __ nitrogen, oxygen or fluorine____
1. what two molecules can not be go in the middle?
2. What does this mean: "the more electronegative atom will get their way"
1. The two atoms that can not go in the middle is Hydrogen and Helium.
2. "The more electronegative atom will get their way" means that the more electronegative atom will attract more electrons towards itself in a bond.
When do you use the linear structure?
What is the degree for a linear structure?
You use a linear structure when the central atom is bonded 2 TIMES, WITH NO LONE PAIRS.
The degree is 180- straight
When do you draw a tetrahedral?
What is the angle?
You draw a tetrahedral when the central atom is bonded 4 TIMES, NO LONE PAIRS.
The angle is exactly 109.5 degrees.
if the difference is greater than 0.5 and less than 1.67, it indicates that the molecule is _______, which means a ______________ is present
if the difference is greater than 0.5 and less than 1.67, it indicates that the molecule is ____polar___, which means a ___dipole___________ is present
dipole-dipole bonding only occurs in ________, _____ molecules that have a ________, and no _________
_________
dipole-dipole bonding only occurs in __polar______, _convalent____ molecules that have a __dipole______, and no ___hydrogen______
___bonding
1. What is the octet rule?
2. What are the three exceptions to the octet rule?
1. Octet rule: Most atom want eight electrons in their valence shell.
2. Exceptions:
Boron and Aluminum can be stable with six electrons.
Hydrogen and helium can only hold 2 electrons.
Beryllium can be stable with only 4 valence electrons.
When do you use bent structure 1?
When the bent structure has 1 lone pair, what's the degree of the angle?
You draw a bent structure when the central atom is bonded TWO TIMES, 1 LONE PAIR.
The angle would be less than 120 degrees.
( It looks similiar to trigonal planar and trigonal planars degree is exactly 120 degrees).
what can you remember about lone pairs when drawing vsepr structures?
Atoms will not be near lone pairs when drawing the structure (lone pairs space them out) and will instead be on the opposite side.
even if a bond is polar, the overall molecule may be non polar if the dipoles _________________
even if a bond is polar, the overall molecule may be non polar if the dipoles ___cancel each other out due to symmetry______________
if a molecule does not have a dipole, then it most likely exhibits _________ which are __________ dipoles.
if a molecule does not have a dipole, then it most likely exhibits ____LDF (London dispersion forces or van der waals)_____ which are ___temporary_______ dipoles.
What is true about elements in the third period or beyond?
Elements in the third period or beyond can hold more than 8 electrons in their valence shell due to available d-orbitals.
When do you draw bent structure 2?
What it the angle of bent structure too?
You would draw bent structure 2 when the central atom is BONDED 2 TIMES, WITH 2 LONE PAIRS.
The angle would be less than 109.5 degrees.
(the same as trigonal pyramid.)
what can you not forget when drawing vsepr structures?
you must draw the electrons around ALL the atoms, even electrons not around the central atom.
how do you draw a dipole arrow? It goes from..
the dipole arrow always goes from the delta positive (s) to delta negatives.
rank the IMFS
What affects them, how do you determine which is strongest?
The higher the imf, the higher the ___________
1. Ionic, Hydrogen bonding, Dipole-Dipole, LDF
Difference in e-neg affect hydrogen bonding, and dipole-dipole interaction (which Ever's difference is higher, will be ranked higher in strength.)
The molar mass affects the strength of LDF (which ever has a higher molar mass will be ranked higher)
The higher the imf, the higher the boiling point