Test 2.1 (Chemical Bonding/C6) Flashcards
(76 cards)
<p>What does VSEPR do?</p>
<p>Analyzes the
repelling effect
between pairs in
shells, both
bonding and lone</p>
<p>octahedral molecular geometry </p>
<p>octahedral -no lone pairs, 90d</p>
<p>Notes on binary molecules covalent</p>
<p>Some molecules have special names: ozone, ammonia, water
Nonbinary molecules (glucose, Tylenol) do not follow these rules</p>
<p>Atomic Mass</p>
<p>mass of one atom of a substance
units: amu</p>
<p>What is the rule for positive or negative charges in a Lewis structure?</p>
<p>A positive charge subtracts an electron, a negative adds an electron. -2 adds two electrons, etc. </p>
<p>naming binary covalent compounds</p>
<p>use prefixes
mono (not used if first element has 1)
di
tri
tetra
penta
hexa
hepta
octa
nona
deca
prefix indicate how many of each
"o" and "a" endings of prefixes are dropped is vowel comes after
1st element in full with prefix (except mono)
2nd element abbreviated with ide ending (i.e. oxide for oxygen)</p>
<p>The direction of a dipole and represented by</p>
<p>The direction of a dipole is from the dipole’s
positive pole to its negative pole. A dipole is represented by an arrow with a head pointing toward the negative pole and a crossed tail situated at the positive pole. </p>
<p>if a molecule's central atom has lone pairs it is...</p>
<p> it is usually a polar
molecule (with some exceptions)</p>
<p>What happens when dipoles point in opposite directions? Where does this occur?</p>
<p> [In molecules of carbon tetrachloride
and carbon dioxide,] the bond
polarities extend equally and symmetrically
in different directions,
canceling each other’s effect and
causing each molecule as a whole to
be nonpolar.</p>
<p>electronegativities difference ionic</p>
<p>1.7-3.3</p>
<p>Dipole-Dipole Interactions</p>
<p>these exist between polar molecules. the partial negative pole of one molecule will be attracted to the partial positive pole of another.
</p>
<p>exceptions to octet rule</p>
<p> hydrogen
forms bonds in which it is surrounded by only two electrons. Boron,
B, has just three valence electrons ([He]2s22p1). Because electron pairs
are shared in covalent bonds, boron tends to form bonds in which it is
surrounded by six electrons</p>
<p>covalent bond</p>
<p>is the chemical bond formed between two atoms when they share electrons in pairs. </p>
<p>Difference between ep geometry and molecular</p>
<p>Ep counts lone pair as an atom, so a trigonal planar with a lone pair would be tetrahedral </p>
<p> London Dispersion Forces</p>
<p>- weak attractive force between molecules that is caused when their electron clouds become distorted
</p>
<p>Dipole ion interactions</p>
<p>- Dipole-ion interactions occur between polar molecules and ions. this will be stronger than a normal dipole-dipole interaction. (interactions between two ions are just ionic bonds)</p>
<p>Covalent compounds with 2-5 nonmetals:</p>
small molecules are usually in what state of matter?
<p>
* Small molecules are usually gases (Ex. nitrogen gas &amp; carbon dioxide)
* </p>
<p> square planar molecular geometry </p>
<p>octahedral-2 lone pairs, 90d</p>
<p>Dipoles</p>
<p>A dipole is created by equal but opposite charges that are separated by a short distance</p>
<p>List how many atoms bonded to the central atom per electron pair geometry.</p>
<p>Linear-2, Trigonal Planar-3, Tetrahedral-4, Trigonal Bipyramidal-5, Octahedral-6</p>
<p>what to do once the single bonds are completed? (Rules of Lewis structure)</p>
<p>Complete octets of terminal atoms. Then complete octets of central atoms if possible. • Check for octets (or two valence electrons in the case of hydrogen). • If atoms do not have octets, create multiple bonds (double, triple...) to make octets.</p>
<p>(Rules of Lewis structure) What to do to make a structural formula once octets are checked?</p>
<p>Usually, erase lone pairs to make a structural formula</p>
<p>key concept of VSEPR</p>
<p>Key concept-electron pairs
will go as far away from
each other as possible</p>
<p>Molecule chart</p>
<p>molecule to polar and non polar bonds. polar bonds to polar molecules/dipoles, and polar and non polar bonds to non polar molecules</p>
Polar molecules act as
Polar molecules act as tiny dipoles because of their uneven charge distribution-depends on types of bonds and shape of molecule
three intermolecular forces
london dispersion forces, hydrogen bonding, dipole-dipole interaction
What do dipole dipole interactions cause?
these interactions cause polar molecules to move around each other in order to maximize contact between oppositely charged poles.
What to do once the atoms are set up? (Rules of Lewis structure)
Create single bonds between all remaining atoms to central atom. Subtract two e from total valence e for each bond made. •
Trigonal pyramidal molecular geometry
Tetrahedral-1 lone pair, <109.5
molecular formula
shows the types and number of atoms in a simple molecule
percent composition
Percentage of each element in a compound by mass Formula: Mass of each element in g per mol ((Mass of element1 divided by mass of compound)100)=percent of element 1
moles to grams or grams to moles. now do example of h202
molar mass-multiply each element's atomic weight by how many atoms are present in the formula, (add the answers if it's a compound,) then use proportion of (g of substance/mol of substance) = molar mass of substance in g / 1 mol
Rules of Lewis structure-what is the first step?
• Count total number of valence electrons on all atoms involved. •
trigonal planar molecular geometry
trigonal planar-no lone pairs, 120d
dipole-dipole | forces
The forces of attraction between polar molecules are known as dipole-dipole forces. These forces are short-range forces, acting only between nearby molecules.The negative region in one polar molecule attracts the positive region in adjacent molecules, and so on throughout a liquid or solid.
symbols and subscripts
* use symbols to represent elements * use subscripts to indicate the amount
bonding occurs with...
bonding occurs with the unpaired valence electrons (to form octet, usually), has to have different spins bc they are being shared
bent molecular geometry
trigonal planar-1 lone pair(<120d), Tetrahedral-2 lone pairs, (<109.5)
electronegativities difference polar covalent
.3-1.7
What dissolves in water?
Polar molecules and ionic compounds (not nonpolar)
non polar covalent electronegativities difference
0-0.3
The bond polarities in a water or an ammonia molecule are what? what does this cause?
The bond polarities in a water or an ammonia molecule are additive, causing the molecule as a whole to be polar. (Ammonia, NH3, and water, H2O, are examples of molecules in which the central atom has both shared and unshared electron pairs )
Axial |
Bonds to non-ring atoms with angles of about 90° are termed axial.
- strongest intermolecular force
Hydrogen bonding
are ionic compounds soluble in water?
Yes
Lone pair
pair of e- on electrons that don't bond
Equatorial
● Bonds to non-ring atoms which make only a small angle compared with the plane of the ring are termed equatorial.
1 mole
6.02*10^23
linear molecular geometry
Linear-no lone pairs, 180d
Free q
Free q!
Trigonal bipyramidal molecular geometry
Trigonal bipyramidal-no lone pairs, 3 equitorial, 2 axial (90d between the equitorials and axials and 120d between the equitorials)
tetrahedral molecular geometry
tetrahedral-no lone pairs, 109.5d
Hydrogen bonding
- a special case of dipole-dipole interactions, where the two dipoles involved are H bonded to N, O, or F (eg, H2O, NH3, HF all have hydrogen bonding between molecules)
rules of what bonds with what
Rules: covalent non metals Ionic nm with m Exception: Florine forms ionic bonds
non polar molecule if:
if a molecule's central atom has no lone pairs, and all of the terminal atoms are the same, or if the dipoles cancel each other out (the angles need to be the same for them to do that)
Rules of Lewis structure-what is the central atom?
If Carbon is present, it is the central atom. Otherwise, the least electronegative element is in the center. (Hydrogen is never the central atom.) •
Which intermolecular force exists between all molecules? How does strength increase?
London dispersion forces exist between all molecules, and are the only significant forces between nonpolar molecules - strength increases with surface area- the more the two molecules can be touching each other, the stronger the dispersion force
HOBrFINCL
All the gases that exist that are diatomic (each of those is those symbols with a two subscript) except for ozone which is o3
what does the subtraction of electronegativities indicate
type of bond
Which interaction are dipole dipole interactions stronger than
- stronger than dispersion forces
VSEPR stands for...
Valence Shell Electron Pair Repulsion
covalent bonds form...
molecules
Molar Mass
mass of one mole of a substance units: g/ mol ***NOTE: An element’s molar mass is numerically the same as its atomic mass
attraction of covalent bonds
When atoms come near each other, their electrons are attracted towards the nucleus of the other atom. If the outside shell is not filled, this attraction becomes stronger.
Terminal atom
non-central atom
the stronger the ___, the stronger the polarity
The stronger difference in electronegativity
Using the molecular geometry, determine if any of the dipole moments will cancel. Any resulting dipole indicates a polar molecule. The bond dipole moments will cancel if:
1. They are of the same magnitude (i.e. the bonds are made with the same element) AND 2. They are symmetrically arranged about the central atom. In the following geometries, the atoms are arranged symmetrically about the central atom: linear, triangular planar, tetrahedral, square planar, triangular bipyrimidal, and octahedral.
Given x grams of a react with excess b, the actual yield of the product1 is y. What is the percent yield of product 1?
Convert x grams of a to mol Found mol of a (1 mol of product 1 from the equation/1 mol of a)= mol of product 1 Convert to grams, then find percent yield
Covalent compounds with 2-5 nonmetals:
large molecules are usually in what state of matter?
