Atomic Bonding

Question 1

What is a mole?

Answer 1

Unit of measurement that contains a number of items equal to Avogadro’s number
Avogadro’s number = 6.022 x 10^23

Question 2

What is an incomplete octet?

Answer 2

Elements that can exist in a stable bonded state even though in this state a full octet isn’t formed
Ex: Hydrogen, Boron, Lithium, Beryllium

Question 3

What is an expanded octet?

Answer 3

The ability to exist in a bonded state with excess electrons

Ex: Phosphorous, and many atoms in the n=3 period and below

Question 4

What are the two main forms of intramolecular bonds?

Answer 4

Ionic and covalent

- van der waals, hydrogen bonds = intermolecular bonds

Question 5

Ionic bond

Answer 5

electrons are completely transferred and the resulting ions are attracted to each other (bonded)
They occur when two atoms have a large difference in electronegativity - if one is more strongly electronegative, it will draw electrons towards it, so much so it steals them
compounds are highly ordered with crystal lattice structure - high melting point in this form
in aq, conduct electricity
alkaline and alkali earth metals tend to form with halogens

Question 6

Covalent bonds

Answer 6

sharing of electrons
bond strength and melting/boiling points lower in these than in ionic
electronegativity difference not great enough to be ionic, but exist on a spectrum to be non-polar or polar

Question 7

Coordinated covalent

Answer 7

electrons aren’t shared from each atom, they’re only shared from one atom’s lone pairs
Ex: Boron trifluoride with ammonia - lone pairs on the ammonia bond with boron (nucleophilic attack)

Question 8

Bond order

Answer 8

describes whether a bond is single, double or triple
singe = sigma
double = sigma plus pi
triple = sigma plus 2 pi

Question 9

Bond Length

Answer 9

Describes length of the covalent bond. Length decreases as order increases (inverse relationship), so single is longest

Question 10

Bond Energy

Answer 10

Bond energy increases as bond order increases (directly proportional)

Question 11

Intermolecular forces

Answer 11

attractions between positive or partially pos, with neg forms of diff molecules
Types: hydrogen, dipole-dipole, van der Waals

Question 12

Hydrogen bonding

Answer 12

attractive force btwn a strongly electronegative atom and a nearby hydrogen atom that is covalently bonded to a strongly electronegative atom
Really only happens with O-H, N-H and F-H molecules. The electroneg atoms are pulling away the electron from H leaving it with a partially pos charge, creating a dipole. Another molecule then can come in and the neg dipole of the electroneg atom will be drawn to the pos dipole of the hydrogen

Question 13

dipole - dipole intermolecular force

Answer 13

same concept of hydrogen bond, just weaker. Other electronegative atoms in covalent bonds have dipoles, but not as strong, but those partially pos and neg charges on the atoms can be attracted to each other

Question 14

Van der Waals or London dispersion

Answer 14

the weakest of forces, same concept of hydrogen bonds but the dipoles exist simply from the movement of electrons randomly. Thus the dipoles are transient
however, if you have a molecule that has a ton of atoms with these transient dipoles, these can build (like a strip of velcro)

Question 15

Formal charge

Answer 15

when a molecule has atoms that has a different number of valence electrons that it “should” have according to the periodic table
Formal charge = VE - 1/2BE - LPE
ve = valence electrons according to the periodic table
be = electrons bonding (2 per bond)
lpe = number of electrons in lone pairs