Electron configuration and hybridisation Flashcards
How would an electron shift from one orbital to another?
If it gained or lost energy
What do s, p, d, and f refer to?
Subshells
Each orbital can fit ___ electrons
2
How many electrons can the s subshell fit?
2
How many electrons can the p subshell fit?
6
How many electrons can the d subshell fit?
10
How many electrons can the f subshell fit?
14
What do (as examples) px and dxz refer to?
Orbitals
What is required for two electrons to occupy the same orbital?
They must have opposite spins - the Pauli Exclusion Principle
In electron configuration notation, what do the numbers refer to, what are they called, and what letter is used to represent them?
The numbers are called principal quantum numbers, they are represented by the letter n, and they refer to energy fields aka shells
Electrons in the outermost shells have ______ energy than those in the innermost shell.
Higher
Remember: The negatively charged electron is attracted to the positively charged proton. It takes more energy to send it further away from the proton.
What formula is used to predict how many electrons can fit into a given shell/energy level?
2n2
How many sub-levels does each energy level have?
The same number as the principal quantum number. So energy level 1 has 1 sub-level, energy level 2 has 2 sub-levels, etc.
What are the levels of electron configuration from broadest to narrowest?
- Energy level/shell
- Sub-level/sub-shell
- Orbital
How many orbitals is in each sublevel?
s = 1
p = 3
d = 5
f = 7
How many electrons can fit in each sublevel?
s - 2
p - 6
d - 10
f - 14
What is the Pauli Exclusion Principle?
That two electrons occupying the same orbital must have opposite spin
In electron configuration, what do arrows pointing up or down indicate?
Electrons spinning in one or the other direction
In which order are orbitals filled (up to 5d)
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f, 5d
How else are the different energy levels sometimes notated?
1 = K
2 = L
3 = M
4 = N
5 = O
6 = P
7 = Q
What is the Aufbau principle?
The principle that electrons fill lower energy fields before higher energy fields (and therefore determines how we determine electron configuration)
What is Hund’s rule?
Before a second electron can be placed in any orbital, all the orbitals of a sub-level must have at least one electron and all must have the same spin.
Write the electron configuration of Bromine (z = 35) in both notation styles
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
[Ar] 4s2 3d10 4p5
From electron configuration notation, how can you figure out how many valence electrons an element has?
These will be the electrons noted separately in noble gas notation.
e.g. Silicon = [Ne]3s23p2 = 4 valence electrons
What are the orbitals in the p sublevel?
px, py, pz
Remember: The subscript refers to the axis the orbital aligns along
What is depicted here?
Hybridised orbitals - sp3
What is the strongest form of covalent bond?
The σ (sigma) bond
How much is the hybridised sp3 orbital influenced by s and p?
s - 25%
p - 75%
Remember: s-orbitals can hold 2 electrons and p orbitals can hold 6. The percentages match this. It’s also contained in the name (1s3p = sp3 orbital)
What are orbitals with the same energy level called?
Degenerate orbitals
What are degenerate orbitals?
Orbitals with the same energy level
Which principle states that electrons fill lower energy fields before higher energy fields
Aufbau principle
Which principle states that before a second electron can be placed in any orbital, all the orbitals of a sub-level must have at least one electron and all must have the same spin.
Hund’s rule
What level of energy would we expect in sp2 orbitals?
About two thirds the energy of the p orbitals
Remember: It’s in the name. The three sp2 orbitals are hybrids of one s and two p orbitals, so they have 33% s character and 67% p character.
Which kind of orbitals make sigma bonds?
Hybridized orbitals
Which kind of orbitals make pi bonds?
Unhybridized orbitals
What kind of bonds can hybridized orbitals make?
Sigma bonds
What is this symbol?
σ
Sigma (lower case)
What kind of bonds are contained in single, double, and triple covalent bonds?
Single: one sigma
Double: one sigma and one pi
Triple: one sigma and two pi
Remember: it’s always only one sigma
Triple bonds are ______ but also _______ than single bonds.
Stronger, shorter
Which type of bond is stronger, pi or sigma?
Sigma
How many sigma and pi bonds are contained in this molecule?
7 sigma
2 pi
Remember: Every single bond is a sigma bond, every double bond is one sigma and one pi bond.
What determines which hybridization will occur in an atom?
The number of “groups” attached to the atom (the steric number). Groups are either bonds or lone pairs. Double and triple bonds are considered one group.
1 group = s
2 groups = sp
3 groups = sp2
4 groups = sp3
5 groups = dsp3
6 groups = d2sp3
What hybridization do we expect in the carbon atom of a methane molecule?
sp3
Remember: In methane (CH4) the carbon atom has four groups attached to it. Four groups means sp3
What characteristics do bonds with higher s character tend to have?
Stronger and shorter
How can you figure out whether one single bond is stronger or weaker than another?
Take the average s-character from their hybrid bonds.
Remember: Bonds with higher percentage of s-character tend to be shorter and stronger. Figure out the hybridisation of the two bonded atoms, then their percentage s-character, then average that percentage.
________ but not ______ electron pairs are counted as groups when determining hybridisation
Localised, delocalised
When do electron orbitals tend to hybridize?
When bonding
What’s the main difference between pi bonds and sigma bonds?
In pi bonds the orbitals overlap along parallel axes, in sigma bonds they overlap along the same axis
What difference in the electron configuration of carbon would we expect between a lone carbon atom, and a carbon in methane?
The lone carbon atom will follow the Aufbau Principle and be configured 1s22s22p2
However the carbon in the methane molecule will form bonds using hybrid orbitals (sp3)
In this case, instead of having two electrons of opposite spin in the 2s sub-level, and two of the same spin in different orbitals of the 2p sub-level, there will be one electron each (same spin) in four hybrid orbitals - like 1s22sp312sp312sp312sp31
Why do single bonds allow for rotation but not double bonds?
Single bonds are sigma bonds - the overlap in orbitals is along the same axis so one side or another rotating doesn’t affect the overlap.
Double bonds have one pi bond. These involve parallel overlap, meaning if one side of the bond rotates, the overlap will be gone.
What is the steric number?
The number of “groups” attached to the atom (sigma bonds and lone pairs) for the purpose of figuring out hybridization type
What effect on molecular geometry does a lone pair have?
It repels covalent bonds more than the bonds repel each other, so the bonds tend to be closer to each other and further from the lone pair.
Why are sp2 bonds shorter than sp3 bonds?
sp2 bonds have a higher s character than sp3 bonds. Since the electron is close to the nucleus in an s orbital, the sp2 orbital is also closer to the nucleus than the sp3 orbital, therefore sp2 bonds are shorter.
What shape would a molecule with an sp2 hybridized central atom take?
If all bonds are in place: Trigonal planar
If lone pairs are present: Trigonal planar bent
What shape would a molecule with an sp hybridized central atom take?
Linear
What shape would we expect a molecule with an sp3 hybridized central atom to take?
If all the bonds are in place: tetrahedral
One lone pair: trigonal pyramidal
Two lone pairs: tetrahedral bent
Identify this molecule shape
Linear
Identify this molecule shape
Tetrahedral, bent
Identify this molecule shape
Tetrahedral
Identify this molecule shape
Trigonal planar bent
Identify this molecule shape
Trigonal planar
Identify this molecule shape
Trigonal pyramidal
