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What is the driving force behind covalent bonds?
satisfying the octet rule by sharing electrons
Covalent bonds are formed by __.
sharing at least one pair of electrons
Every covalent bond has a characteristic __ that leads to __. This is the __.
- maximum stability
- bond length
Bond Dissociation energy
energy required to break a covalent bond in an isolated gaseous molecule is called this
What happens with energy in terms of breaking a bond?
always add energy
True or False
Each group of atoms will have their own separate bond length.
What kind of bond?
Metal and nonmetal
What kind of bond?
With ionic bonds, why is melting and boiling part higher (harder to melt)?
the network structure makes it harder
Why are covalent bonds the strongest bonds?
when you melt them, you break the interactions, not the molecules themselves like ionic bonds
What is the max amount of covalent bonds that can be formed?
Ionic bonds (in terms of charge)
full charges on elements
Poalr covalent bonds
- bonding electrons are attracted more strongly to one element than the other
- unequal distribution
What is one way to tell you have ionic substances?
- whether it conducts electricity when dissolved in water
- Heat it up to a liquid
Diatomic atoms are always __ covalent bonds.
Bond polarity is due to __ between atoms.
What is electronegativity
the ability of an atom in a molecule to attract the shared electrons in a covalent bond
What is the periodic trend in terms of electronegativity?
- it increases from left to right
- It decreases from top to bottom
- Noble gases not involved
% Ionic Character: __
as a general rule for two atoms in a bond, we can calculate the electronegativity difference
What is the definition for electronegativety?
deltaEN= EN(Y)-EN(X) for X-Y bond
What are the rules for electronegativity difference?
- If it is less than 0.5, it is nonpolar covalent
- If greater than 0.5 but less than 2.0, it is polar covalent.
- If greater than 2.0, it is ionic
Using __, teh valence electrons in an element are represented by dots.
What are valence electrons?
- electron-dot (Lewis) structures
- those electrons with the highest principal quantum number n
What does the octet rule apply to?
- Those electrons before the 3d level
- Atoms in the third row or lower, which are larger and can accomodate more bonded atoms
What is it called when you have more than eight electrons in the valence shell?
Where do the extra pairs go?
- expanded octet
- into unfileld d orbitals
A molecule like O3 has a bonding characteristic that __.
both structures are correct, but neither is correct by itself.
When multiple structures can be drawn, the actual structure is an __ of all possibilities.
The average is called a __. What indicates this?
- resonance hybrid
- straight double headed arrow
Tje motrate opm, NO3-, has three equivalent oxygen atoms, and its electron structure is a __ hybrid of three electron dot structures.
What is formal charge?
We determine __ and estimate the more __.
- determines hte best resonance structure
- formal charge
- accurate representation
How to determine formal charge?
Formal charge= (# of valence electrons)- (# of bonding electrons/ 2)- (# of nonbonding electrons)
What does VSEPR stand for?
valence shell electron pair repulsion model
VSEPR: Electrons in bonds and in lone pairs can be though t of as __ that __ one another and stay as __ as possible, thus causing molecules to assume specific shapes.
- charge clouds
- far apart
Two Charge Clouds:
- electron groups point in opposite directions
Three Charge Clouds?
- electron groups lie in same plane and point to the corners of an equilateral triangle
- angular or bent
Four Charge Clouds and shapes
- electron groups point to the corners of a regular tetrahedron
- Four Charge Clouds with:
- - four electrons: tetrahedron
- - three electrons: trigonal pyramidal
- - two: bent
Five charge clouds and shapes
- electron gorups point to the corners of a trigonal bipyramid
- five electrons: trigonal bipyramidal
- four electrons: seesaw
- Three: T- shaped
- two electrons: linear
Six Charge Clouds and Shapes
- electron groups point to the corners of a regular octahedron
- Six electrons: octahedron
- five electrons: square pyramidal
- four: square planar
What is Valence Bond Theory:
a quantum mechanical model which shows how electron pairs are shared in a covalent bond
Bonds form between two __ of the same phase. A __ bond forms from head on orbital overlap.
said wave functions from s orbitals and p orbitals could be combined to form hybrid atomic orbitals
What is the hybridization of two charge clouds?
What is the hybridization of three charge clouds?
What is the hybridization of fourcharge clouds?
The __ provides a better explanation of chemical and physical properties than the __.
- molecular orbital (MO) model
- valence bond (VB) model
- probability of finding hte electron within a given region of space in an atom
- probability of finding the electron within a given region of space in a molecule
__ of orbitals is __ in energy than two isolated __ orbitals and is called a __.
- additive combination
- bonding moleclar orbital
__ of orbitals is __ in energy than two isolated __ orbitals and is called an __.
- Subtractive combinations
- antibonding molecular orbital
all electrons are spin-paired. It is weakly repelled by magnetic fields.
There is at least one unpaired electron. It is weakly attracted by magnetic fields.
Oxygen, O2, is predicted to be __ by electron-dot structures and valence bond theory. However, it is known to be __.
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