dihelium - 2024 ACF Winter

Question

This molecule composed of excited atoms was the first observed Rydberg molecule. For 10 points each:

[10h] Name this molecule, whose fully filled sigma-1s and sigma-star-1s molecular orbitals with no other MOs give it a bond order of zero. This molecule’s bond length of 5200 picometers makes it the largest diatomic molecule.

ANSWER: dihelium [or helium dimer; or He₂; reject “helium”]

[10e] Despite having zero bond order in MO theory, dihelium is held together very weakly by these intermolecular forces named for a Dutch physicist. London dispersion and dipole-dipole interactions contribute to these forces.

ANSWER: van der Waals forces

[10m] Dihelium molecules have been observed to fit inside these other compounds in a host-guest relationship. These allotropes are denoted with the formula C-sub-x, where x is the number of atoms within the compound.

ANSWER: fullerenes [accept buckminsterfullerenes or buckyballs]

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Summary


2024 ACF Winter at UC Berkeley	2024-11-16	Y	3	23.33	100%	100%	33%
2024 ACF Winter at Clemson	2024-11-16	Y	8	13.75	100%	38%	0%
2024 ACF Winter at Lehigh	2024-11-16	Y	7	14.29	100%	29%	14%
2024 ACF Winter at Northwestern	2024-11-16	Y	9	14.44	100%	44%	0%
2024 ACF Winter at Ohio State	2024-11-16	Y	7	18.57	100%	57%	29%
2024 ACF Winter at Online	2024-11-16	Y	8	12.50	88%	38%	0%
2024 ACF Winter at UBC	2024-11-16	Y	2	10.00	100%	0%	0%
2024 ACF Winter at Central Florida	2024-11-16	Y	5	12.00	100%	20%	0%

Data


Berkeley A	Stanford L	10	10	10	30
Berkeley C	Berkeley B	0	10	10	20
Stanford M	Stanford A	0	10	10	20
Alabama A	Auburn C	0	10	0	10
Auburn A	Clemson A	0	10	10	20
Georgia Tech A	Emory B	0	10	0	10
Georgia Tech B	Georgia A	0	10	10	20
Georgia Tech C	Georgia Tech D	0	10	0	10
Georgia Tech F	Emory A	0	10	0	10
South Carolina A	Tusculum A	0	10	0	10
Georgia Tech E	Tennesse A	0	10	10	20
Columbia A	Penn State B	10	10	10	30
Penn State A	Columbia B	0	10	0	10
Johns Hopkins A	Rowan A	0	10	0	10
Penn A	Johns Hopkins B	0	10	10	20
Lehigh A	Princeton A	0	10	0	10
Rutgers A	Haverford A	0	10	0	10
Rutgers C	Bard	0	10	0	10
Indiana B	WashU D	0	10	0	10
Purdue A	Miami	0	10	10	20
WashU B	Northwestern A	0	10	10	20
UChicago C	Notre Dame	0	10	10	20
Indiana A	Purdue C	0	10	0	10
Purdue D	UChicago B	0	10	0	10
UIUC A	SIUE A	0	10	0	10
UIUC C	UChicago D	0	10	0	10
UChicago A	WashU C	0	10	10	20
Pitt A	CWRU B (UG)	0	10	10	20
Kenyon A (UG)	Michigan D (DII)	0	10	0	10
Michigan A	Michigan C (UG)	0	10	10	20
Ohio State A (UG)	Michigan B	10	10	10	30
Michigan State A	CWRU A (UG)	10	10	10	30
Michigan State B (UG)	CWRU D (DII)	0	10	0	10
Pitt B (UG)	CWRU C (UG)	0	10	0	10
Vassar B	Colorado College	0	10	0	10
McGill E	Texas B	0	10	0	10
Missouri	NYU B	0	10	10	20
NYU A	Vassar A	0	10	10	20
Texas D	Ole Miss	0	0	0	0
Mississippi State	Texas A	0	10	0	10
Texas C	Oregon State	0	10	0	10
Iowa	WUSTL A	0	10	10	20
UW B	SFU	0	10	0	10
UW A	UBC B	0	10	0	10
Florida Tech A	Florida Tech B	0	10	0	10
UF E	UCF B	0	10	10	20
UF C	UF B	0	10	0	10
UF A	UF D	0	10	0	10
UCF A	UF F	0	10	0	10