Flashcards in Term Test 1 Vocab Deck (56)
two electrons shared between 2 nuclei (localized covalent bond)
flat molecule, has pi bond/sp2 orbitals, bond angle of 120°
pyramid shaped, sp3 hybridized, 4 substituents or 3 and a lone pair, bond angle is 109.5°
3 p orbitals blended with 1 s, cannot form a pi bond as all p orbitals are already used in sigma bond
localized electrons, overlap of sp3 orbital and p orbital
Which orbital is involved in pi bond
p orbital excluded from sp2 hybridization will be involved in pi bonding
delocalized, easily broken
sp orbitals, two pi bonds formed from the two p orbitals not involved in hybridization, bond angle of 180°
Is a double bond twice as strong as a single bond?
No, because pi bond is weaker than sigma bond and a double bond is composed of a pi and sigma bond.
Difference between polar and polarizable
Polar is when one atom in a molecule carries a negative charge more than the other one (ex. H - Cl, chlorine is more negative). Polarizable is the response of the bond to a dynamic system, electrons of larger molecules are further from nucleus and can be pulled away more easily.
The larger the atom...
...the more likely the bond can be polarized. A temporary dipole movement can be formed just by electron fluctuations around the atom.
Electronegativity increases and decreases in which way on periodic table?
Decreases as you go down a period, and increases as you go across the period.
Give examples of groups that donate electrons
Electron donating groups have low electronegativity and include: CH3, CH2CH3, Li, Mg, Al (metals)
measurable property that describes a separation of charge in the molecule, vector sum of all bond dipoles
Electron numbers of common elements
1 - H, Li
4 - C
5 - N, P
6 - O, S
7 - Cl, Br, F
electron bookkeeping, sum of all formal charges must equal overall charge of the molecule.
formal charges can give you info about?
releases energy (this is why atoms bond because they are more stable bonded than separate)
lowest energy orbitals fill first. 1s, 2s, 2p, 3s, 3p, 4s, 3d
electrons have up spin and downspin only 2 e- can occupy an orbital and must have opposite spin
If two or more empty orbitals of equal energy are available, one electron occupies each with parallel spins until all orbitals are half full.
Why are sp3 bonds strong?
the orbitals are oriented strongly in a certain direction so it allows for better overlap of orbitals in a bond.
Bond character of CH4 molecule
each C-H bond has strength of 439 kJ/mol and bond angle of 109.5°, length of 109 pm.
- do not change geometry of molecule in ANY WAY
- forms only differ in their placement of pi bond electrons and lone pairs
- one alone is wrong, molecule is blend of all of them, though some are upweighted
Resonance Rules (in order of most importance)
1. Number of pi bonds - delocalization of electrons stabilizes the molecule so form with most pi bonds makes greatest contribution to its stability (don't move pi bonds from benzene ring, it will decrease stability)
2. formal charges - fewer formal charges are more important. If forms have equal numbers of formal charges then the form that has the most EN atoms carrying neg charge and least EN atoms carrying pos charge is better
3. Inductive effects - electron donating groups (alkyls) help to stabilize positive charge (give electrons to positive site), electron withdrawing groups (halogens, O, N) pull electrons and thus stabilize negative charge.
Why is the terminal carbon on allene twisted? (C3H4)
middle carbon is sp hybridized, is bonding with two carbon substituents which are sp2 hybridized. The two empty orbitals on the middle carbon are not on the same plane and thus the pi bonds formed are at different angles.
Similarities in structure imply...
similarities in properties and behaviour