GenChem3 (Bonding and Chemical Interactions) Flashcards
Forces within a molecule that are weaker than the chemical bond but still play an important role in the physical properties of many substances
Intermolecular Forces
What is the octet rule?
What are the exceptions?
It states that an atom tends to bond with other atoms until it has eight electrons in its outermost shell, to form a stable electron configuration.
Hydrogen, lithium, beryllium, boron, and elements beyond the second row.
Why is hydrogen an exception to the octet rule? Lithium? Beryllium? Boron? Elements beyond the 2nd row?
Hydrogen can only have 2 valence electrons
Lithium Can only attain 2 valence electrons
Beryllium can only attain 4 valence electrons
Boron can only attain 6 valence electrons
Elements beyond the 2nd row can expand octets to include more than 8 by incorporating d-orbitals
A bond formed when a smaller atom with a smaller ionization energy is transferred to an atom with a greater electron affinity, resulting in ions being held together by electrostatic force
Ionic Bond
Type of bonding where an electron pair is shared between two atoms
Covalent Bonding
A covalent and partially ionic bond is a
Polar covalent bond
When two atoms with large differences in electronegativity react, there is complete transfer of electrons from the less electronegative atom to the more electronegative atom. This is what type of bonding?
Ionic Bonding
The atom that loses electrons is the
The atom that gains electrons is the
Cation (positively charged)
Anion (negatively charged)
What value must the difference between two electronegativities of two atoms be for ionic bonding to occur?
1.7
Elements of group VII often form ionic bonds with groups..
I and II
The electrostatic force of attraction between the charged ions is called an…
ionic or electrovalent bond
Ionic compounds have HIGH/LOW melting/boiling points
Why?
Ionic compounds have high melting/boiling points
Due to the strong electrostatic forces between the ions
Under what circumstances can ionic compounds conduct electricity?
Liquid and aqueous state, not the solid state
What structure do ionic solids form, consisting of infinite arrays of positive and negative ions in which the attractive forces between ions of opposite charge are maximized, while repulsive forces between ions of like charge are minimized
Crystal Lattice
Covalent compounds are HIGH/LOW melting
Covalent compounds are SOLID/LIQUID/GAS
Covalent compounds CONDUCT/DON’T CONDUCT ELECTRICITY in liquid states
Covalent compounds are LOW melting
Covalent compounds are SOLID
Covalent compounds DON’T CONDUCT electricity
Can atoms share more than one pair of electrons?
Yes. Duh.
The average distance between the two nuclei of the atoms involved in a covalent bond
As the number of electron shares increases, what happens to this variable?
Bond Length
It decreases
The energy that is required to separate two bonded atoms.
Bond energy
The shared valence electrons of a covalent bond are called the
The valence electrons that are not involved in the covalent bond are called this, or…
Bonding Electrons
Non-bonding Electrons, lone pair electrons
Lewis structures represent which orbitals of electrons?
s and p valence orbitals
Which atom is usually the center atom?
Which atoms usually occupy the end position?
The least electronegative atom typically is the center atom
Hydrogen and the halogens typically are on the end position
What is the equation for the formal charge of an atom in a molecule?
Formal charge = V-1/2N(bonding)-N(Nonbonding)
V=Valence electrons in free atom
N=number of electrons
True/False: More stable resonance structures contribute more to the resonance hybrid
True!
True/False: A Lewis structure with formal charge is preferred to one with no formal charge
True/False: A Lewis structure in which negative formal charges are placed on more electronegative atoms is more stable than one in which formal charges are placed on less electronegative atoms
False!
True!
True/False: Atoms found in or beyond the third period can have more than eight valence electrons
True!
They can be assigned more than four bonds
In the sulfate ion (SO4)^-1, how many bonds and valence electrons can sulfur hold?
6 bonds, 12 valence electrons
Polar covalent bonding occurs between atoms with small differences in electronegativity, what is the range of electronegativity difference (generally)?
0.4-1.7 Pauling Units
The equation for the dipole moment (u) in polar covalent bonds is
u = qr [C*m]
q=product of the charge magnitude
r= distance between two charges
This type of covalent bond occurs between atoms that have the same electronegativities, and occurs commonly in diatomic bonds (N2, H2, etc)
Nonpolar covalent bond
This type of bond occurs when a shared electron pair comes from the lone pair of one of the atoms in the molecule. It is commonly seen in Lewis acid-base compounds
Coordinate Covalent Bond
What is a Lewis acid?
What is a Lewis base?
A Lewis acid accepts an electron pair
A Lewis acid donates an electron pair
T/F: A molecule nonpolar bonds is always nonpolar
T/F: A molecule with polar bonds is always polar
True!
False! Polar bonds can be arranged in a nonpolar fashion about an atom
When two atoms bond to form a molecule, the atomic orbitals interact to form a _______, which describes the probability of finding the bonding electrons.
Molecular Orbital
If the sign of two atomic orbitals are the same, this is formed
If the sign of two atomic orbitals is different, this is formed
Bonding Orbital
Anti-bonding orbital
When orbitals overlap head to head, the resulting bond is called a
When orbitals are parallel, a ___ bond is formed
sigma bond
pi bond
The attractive forces that exist between molecules are collectively known as
Dipole-dipole interactions and dispersion forces are often referred to as
Intermolecular Forces
Van der Waals forces
Type of intermolecular force where the positive region of one molecule is close to the negative region of another molecule
Dipole-Dipole Interaction
In what phase do dipole-dipole interactions become negligible?
Why?
Gas
The molecules are much farther apart
Which tend to have higher boiling points, polar species or nonpolar species?
Polar species
A specific and unusually strong form of dipole-dipole interaction which may be either intra- or inter molecular. Occurs with hydrogen atoms due to slight positive charge.
Hydrogen bonding
Do substances that exhibit hydrogen bonding have unusually high or unusually low boiling points?
Why?
Unusually high
It is difficult to break the hydrogen bonds
Attraction between neighboring molecules resulting from the short lived dipoles created by the random location of covalently bonded electrons within the molecules
London Dispersion Forces
Dispersion forces are generally STRONGER/WEAKER than other intermolecular forces
When are they most important?
Dispersion forces are generally WEAKER than other intermolecular forces
They are most important when molecules are close together, not far apart.
The strength of dispersion forces within a given substance depends directly on how easily the electrons in the nucleus can….
Therefore, do larger or smaller molecules possess greater dispersion forces?
move aka, be polarized.
Larger molecules have electrons further from the nucleus, so they possess greater dispersion forces
The low temperature at which the noble gases liquefy is to some extent indicative of the magnitude of __________ between the two atoms.
It is the only intermolecular force that exists between noble gas atoms.
Dispersion forces
