Periodic Trends
Chemical Formulas and Structures
Bond Basics
Bond Theories
Ochem and Hybridization
100
Describe the trend of electron affinity across a period and down a column.
(30 seconds)
Increases across a period
Decreased down a column
100
State the preferred oxidation state of Ar.
(30 sec)
0 - Argon is a noble gas and does not like to bond or react.
100
Why do elements form bonds?
(30 sec)
To reduce their potential energy.
To achieve a lower energy state.
100
Which bond theory allows us to visualize orbital interaction in 3d space.
(30 sec)
Valence Bond Theory (VBT)
100
What is an alkyne?
(30 sec)
Any organic compound containing at least 1 carbon to carbon triple bond.
200
Majority of the observable trends on the periodic table are as a result one basic atomic property. What is this atomic property called?
(30 seconds)
Effective Nuclear Charge (Zeff)
200
Identify the oxidation states in the following compound: Na2SO4
(1 min)
Na = +1 (x2) = +2
S = +6
O = -2 (x4) = -8
200
What is the octet rule and how does it pertain to bonding?
(1 min)
All atoms want to have a full outer shell. (in most cases this means just a full s and p orbital which is 8 total electrons)
Atoms will bond in a manner that will ensure this occurs.
200
Are pi bonds cylindrically symmetric? Why or why not?
(1 min)
No, by VBT, if you rotate pi bonds 180 degrees on a horizontal axis, the phases of the overlap flip.
200
What would be the hybridization state of a carbon involved in a triple bond?
sp
300
Would it be easier to remove an electron from Sodium or Potassium? Which of these would handle being a cation the best.
(1 min)
Potassium has a lower Zeff than Sodium, resulting in a lower EN, EA, and IE. This means it is much easier to remove an electron from Potassium than Sodium.
Additionally, Potassium has a larger atomic radius, meaning electron density is already low so it will "notice the difference less than Sodium"
300
Make a proper chemical formula using the following elements and state oxidation states.
(1 min)
Ca2Ge
Ca = +2 (x2) = +4
Ge = -4
300
Rank the following compounds from least ionic to most ionic:
MgS, N2O, HF, RbI
(1 min 30 sec)
N2O < MgS < RbI < HF
300
A student makes an MO diagram for two different atoms. He finds that there are 12 bonding electrons and 8 antibonding electrons. What type of bond will the two atoms form?
(1 min)
Double bond.
300
Identify at least two functional groups in the following molecule:
Sulfhydryl, amine, carboxylic
400
Please explain why, when offered excess electrons, Flourine would be a much better electron acceptor than Chlorine. Explain using at least 3 periodic trends.
(1 min 30 seconds)
Flourine has a higher EN and EA than chlorine, meaning it wants electrons more than chlorine does.
Flourine has a higher Zeff so it has greater ability to attract outer electrons.
Flourine has a smaller atomic radius which means its electron cloud is smaller, resulting in higher probability electron density.
400
Draw the Lewis Structure for the polyatomic ion chromate. State formal charge and net formal charge.
(1 min.)
(draw on whiteboard)
400
Rank the following from lowest bond length (BL) to highest bond length and from lowest bond dissociation energy (BDE) to highest bond dissociation energy (BDE): triple bond, double bond, single bond
(1 min)
single bond < double bond < triple bond
BL and BDE
400
Please explain using MO Diagrams and Bond order why it is not possible to form a multiple bond greater than a triple bond.
(3 min)
You would have to fill higher energy bonding orbitals and skip lower energy antibonding orbitals which violates Aufbau principle.
400
Please write the molecular formula for the following compound.
C14H10O3
500
Explain the phenomenon of Lanthanide Contraction using periodic trends.
(2 min)
Outer f-orbitals do not experience nuclear charge as much as they would like to. Due to degeneracy, these orbitals can penetrate into inner d-orbitals. This increases the Zeff experienced by the outermost orbitals. Higher overall Zeff means atomic radius will decreases, resulting in Lanthanide Contraction of electron cloud.
500
Draw the most stable Lewis structure for the compound [SGeN]-. Explain why this structure is the most stable.
(2 min)
S = G = N
N should have negative formal charge because it is most EN.500
Explain why structures that have resonance display hybrid bond character.
(1 min 30 sec)
Resonance means that there are delocalized electrons in pi bonds. These electrons can move around the structure, forming pi bonds wherever possible. All of these resonance structures contribute to a resonance hybrid which is a true representation of the molecule. Since each resonance capable bond is not always a single bond but not always a multiple bond, it displays hybrid bond character of a bond in between a single bond and a multiple bond.
500
Please explain what type of bond is formed in an O22- molecule using an MO Diagram and Bond Order.
(3 min)
single bond
500
Please state how many atoms are in an sp2 hybridization state in the structure below:
13
6 carbons from each benzyl ring, 1 oxygen =
6 + 6 + 1 = 13