FINAL EXAM- VESPR Flashcards
Electronegativity
measure of the ability of an atom in a compound to attract electrons from another atom in a compound. The attraction an atom has for a pair of electrons in a bond.
Polar covalent bond
A covalent bond in which a pair of electrons shared by two atoms is held more closely by one atom. Unequal sharing.
Nonpolar covalent bond
A covalent bond in which the bonding electrons are equally attracted to both bonded atoms. Perfect sharing, same attraction.
Dipole
A molecule or part of a molecule that contains both positively and negatively charged regions. “little bit”
Linear
A molecule whose atoms are arranged so that the bond angle between each is 180 degrees.
Angular
aka bent, a molecule whose atoms are arranged so that the bond angle between each is 105 degrees.
Trigonal planar
A molecule whose atoms are arranged so that the bond angle between each is 120 degrees.
Trigonal pyramidal
A molecule whose atoms are arranged so that the bond angle between each is 107 degrees.
tetrahedral
A molecule whose atoms are arranged so that the bond angle between each is 109.5 degrees.
Polar molecule
molecules with uneven geometric distribution of dipoles.
Nonpolar molecule
Even geometric distribution of dipoles or no dipoles.
Van der Waal forces
AKA London dispersion forces. The attraction of intermolecular forces between molecules.
Dipole-Dipole attraction
attraction between polar molecules. Each molecule has polar bond and based on shape, bond doesn’t cancel geometrically.
London Dispersion forces
All molecules display this type of IMF, but it is the only IMP in nonpolar molecules.
Hydrogen bonds
The intermolecular force occurring when a hydrogen atom that is bonded to a highly electronegative atom of one molecule is attracted to two unshared electrons of another molecule. Type of Dipole-Dipole attraction, very strong, the strongest IMF, only occurs in molecules that have hydrogen bonded to a highly electronegative atom (O, F, Cl, and N)
Intermolecular forces
forces between molecules.
Intramolecular forces
any force that holds together the atoms making up a molecule or compound. Aka covalent and ionic bonds.
Bond strength
The strength with which a chemical bond holds two atoms together
Bond length
The average distance between nuclei of two bonded atoms in a molecule.
Given electronegativities be able to determine bond type.
- Take the two given electonegativities and subtract the smaller one from the bigger one.
- If the difference is 0-0.4, it is nonpolar covalent
- If the difference is greater than 0.4 and less than or equal to 1.9 it is polar covalent
- If the difference is above 1.9 it is ionic
Determine bond type from the relative position of the elements on the periodic table
- If the two elements are very far away from each other, they are ionic
- If the two elements are close together, they are covalent.
- Kind of close=polar covalent
- Really close=nonpolar covalent
Know how to draw Lewis dot diagrams and exceptions
- Write each individual element symbol and the number of them in the compound (subscript)
- Put the least electronegative one (usually the ones there’s less of) in the middle and even space the symbols of the other element around it.
- Draw the number of valence electrons the element has around each symbol representing them with dots or x’s.
- Draw circles so that each element has 8 valence electrons
- The only exceptions to the 8 valence electrons is that H has 2, B has 6, and Be has 4.
Know how to draw a line structure
- Arrange the symbols in the same way you would if you were drawing a lewis dot diagram
- Instread of using dots, represent pairs of electrons with lines, including bonded pairs
Be able to determine one of 5 molecular shapes
- Choices are Linear, trigonal pyramidal, tetrahedral, trigonal pyramidal, and angular/bent
- You can determine which one it is by counting the number of lone pairs vs bonded pairs.
Lone pairs
the pairs of electron around the center atom that are not bonded and bonded pairs are the pairs of electrons between two elements.
lone/bonded for the shapes
- 0/2=linear
- 0/3= trigonal planar
- 0/4=tetrahedral
- 1/3=trigonal pyramidal
- 2/2=angular/bent
Be able to determine whether a molecule is polar or nonpolar
- First determine if the bonds are polar or nonpolar by subtracting the electronegativities
- If it has polar covalent bonds, it has dipoles
- If there are nonpolar covalent bonds, there are no dipoles
- If there are no dipoles, its automatically nonpolar
- Next you have to look at the shape
- If the angles are even and cancel out, its nonpolar
- If the angles are uneven and don’t cancel out, its polar
- Think of dogs on leashes
- More often its nonpolar I
Be able to determine the intermolecular force displayed between molecules
- Choices are Hydrogen bond, Dipole-Dipole, and London Dispersion
- H bond if it contains Hydrogen
- Dipole-Dipole if its molecular polarity is polar
- All have LDF
Know the effect of intermolecular forces on dissolving and phase change
- The strength of attractive forces between particles determines a substance’s phase at room temperature
- The stronger the attraction, the harder it is to change phases, and the more solid it will be
- The weaker the attraction, the easier it is to change phases and will be gaseous
- Like dissolves like so for example, D-D will dissolve easily in D-D
