calcium oxide

Formula: CaO
Molecular weight: 56.077
IUPAC Standard InChI: InChI=1S/Ca.O
IUPAC Standard InChIKey: ODINCKMPIJJUCX-UHFFFAOYSA-N
CAS Registry Number: 1305-78-8
Chemical structure:
This structure is also available as a 2d Mol file
Other names: Calcium monoxide
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Gas phase thermochemistry data

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Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	43.93	kJ/mol	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	219.71	J/mol*K	Review	Chase, 1998	Data last reviewed in June, 1973

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
C_p = heat capacity (J/mol*K)
H° = standard enthalpy (kJ/mol)
S° = standard entropy (J/mol*K)
t = temperature (K) / 1000.

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Temperature (K)	4500. to 6000.
A	358.0508
B	-117.9888
C	16.67943
D	-0.832390
E	-615.0940
F	-713.7737
G	172.4967
H	43.93200
Reference	Chase, 1998
Comment	Data last reviewed in June, 1973

Condensed phase thermochemistry data

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Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_liquid	-557.33	kJ/mol	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
S°_{liquid,1 bar}	62.31	J/mol*K	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_solid	-634.92 ± 0.90	kJ/mol	Review	Cox, Wagman, et al., 1984	CODATA Review value
Δ_fH°_solid	-635.09	kJ/mol	Review	Chase, 1998	Data last reviewed in June, 1973
Quantity	Value	Units	Method	Reference	Comment
S°_{solid,1 bar}	38.1 ± 0.4	J/mol*K	Review	Cox, Wagman, et al., 1984	CODATA Review value
Quantity	Value	Units	Method	Reference	Comment
S°_solid	38.19	J/mol*K	Review	Chase, 1998	Data last reviewed in June, 1973

Liquid Phase Heat Capacity (Shomate Equation)

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Temperature (K)	3200. to 4500.
A	62.76000
B	4.629681×10^-7
C	-1.092037×10^-7
D	8.966312×10^-9
E	6.504656×10^-7
F	-591.8059
G	116.8909
H	-557.3339
Reference	Chase, 1998
Comment	Data last reviewed in June, 1973

Solid Phase Heat Capacity (Shomate Equation)

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Temperature (K)	298. to 3200.
A	49.95403
B	4.887916
C	-0.352056
D	0.046187
E	-0.825097
F	-652.9718
G	92.56096
H	-635.0894
Reference	Chase, 1998
Comment	Data last reviewed in June, 1973

Gas phase ion energetics data

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Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
LL - Sharon G. Lias and Joel F. Liebman
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	6.66 ± 0.18	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	1190.6	kJ/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	1162.3	kJ/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
6.66 ± 0.18	END/DER	Dalleska and Armentrout, 1994	LL
6.5 ± 0.3	EVAL	Belyaev, Gotkis, et al., 1990	LL
7. ± 1.	EI	Farber, Srivastava, et al., 1987	LBLHLM
6.9 ± 0.15	DER	Murad, 1983	LBLHLM
7. ± 1.	EI	Farber and Srivastava, 1976	LLK
6.5	EI	Drowart, Exsteen, et al., 1964	RDSH

Constants of diatomic molecules

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Data compiled by: Klaus P. Huber and Gerhard H. Herzberg

Data collected through September, 1976

Symbols used in the table of constants
Symbol	Meaning
State	electronic state and / or symmetry symbol
T_e	minimum electronic energy (cm^-1)
ω_e	vibrational constant – first term (cm^-1)
ω_ex_e	vibrational constant – second term (cm^-1)
ω_ey_e	vibrational constant – third term (cm^-1)
B_e	rotational constant in equilibrium position (cm^-1)
α_e	rotational constant – first term (cm^-1)
γ_e	rotation-vibration interaction constant (cm^-1)
D_e	centrifugal distortion constant (cm^-1)
β_e	rotational constant – first term, centrifugal force (cm^-1)
r_e	internuclear distance (Å)
Trans.	observed transition(s) corresponding to electronic state
ν₀₀	position of 0-0 band (units noted in table)

Diatomic constants for ⁴⁰Ca¹⁶O
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
Progression of absorption bands (ΔG ~ 850) in Kr and Xe matrices, 20000 - 26000 cm^-1; observed for both Ca¹⁶O and Ca¹⁸O, but not definitely assigned.
↳Brewer and Wang, 1972
										(B → A')
↳Lejeune, 1945; Gaydon, 1955; missing citation; Volnyets, Kovalenok, et al., 1974
Orange system of strong emission bands, 15700 - 16700 cm^-1; no analysis.
↳Lejeune, 1945; Gaydon, 1955; missing citation; missing citation
C ¹Σ⁺	28857.8	560.9 Z	4.₀		0.3731 1	0.0032		(0.0000007)		1.989	C ↔ x 2 R	28772.4 Z
C ¹Σ⁺	↳missing citation; Veits and Gurvich, 1967
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
B ¹Π	25991	[574.4] Z			0.388₂ 3 1	0.005₅		(0.0000007)		1.950	B ↔ X 4 R	25913.0 Z
B ¹Π	↳Lagerqvist, 1954; Veits and Gurvich, 1967
A ¹Σ⁺	11554.8	718.9 Z	2.11		0.4059₂ 5	0.00137		5.4		1.9067	A → X R	11548.8₄ Z
A ¹Σ⁺	↳missing citation; missing citation; Brewer and Hauge, 1968; Field, 1974
A' ¹Π	8433	545.7 H	2.54		0.337	0.002₁				2.09₃	A' → X 6 R	8340
A' ¹Π	↳missing citation
a ³Π_i	(8313) 7	556	3.3		0.335					2.099
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
X ¹Σ⁺	0	732.1₁ Z	4.8₁ 8		0.4445₂			6.5₈ 9		1.8221	10

Notes

Perturbations.

ξ system of Lejeune and Rosen, 1945.

Value of B^Q; B^PR - B^Q = +0.0005.

η system of Lejeune and Rosen, 1945.

Many rotational perturbations by A' ¹Π and a ³Π_i Hultin and Lagerqvist, 1951, Field, 1974.

Directly observed for v' > 9 only; vibrational numbering determined from the perturbations in A ¹Σ⁺ Field, 1974.

A = -58, from perturbations in A ¹Σ⁺ as are the other constants for this state; see Field, 1974.

The vibrational constants in the Table are derived from levels with v ≤ 4 Hultin and Lagerqvist, 1951, Lagerqvist, 1954. From band heads in the A-X system (v" ≤ 13) and accounting for head-origin separations, Brewer and Hauge, 1968 have derived ω_e= 733.4 Brewer and Hauge, 1968, ω_ex_e= 5.28 Brewer and Hauge, 1968.

missing note

The question whether this is the ground state was for long in doubt but the observation by Ault and Andrews, 1975 of a fundamental frequency of 707 cm^-1 in a nitrogen matrix seems to settle it: see also Field, 1974 and the theoretical work of Carlson, Kaiser, et al., 1970. For computed ¹Σ ground state properties see Yoshimine, 1968.

From the Ca + ClO₂ chemiluminescence spectrum Engelke, Sander, et al., 1976. By contrast, the most recent mass-spectrometric Colin, Goldfinger, et al., 1964, Drowart, Exsteen, et al., 1964 and flame-photometric Kalff and Alkemade, 1973 determinations - corrected, where necessary, for a ¹Σ ground state - lead to D₀⁰ = 4.04 eV Kalff and Alkemade, 1973.

References

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Gas phase ion energetics data, Constants of diatomic molecules, Notes

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

Cox, Wagman, et al., 1984
Cox, J.D.; Wagman, D.D.; Medvedev, V.A., CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, 1. [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Dalleska and Armentrout, 1994
Dalleska, N.F.; Armentrout, P.B., Guided ion beam studies of reactions of alkaline earth ions with O₂, Int. J. Mass Spectrom. Ion Processes, 1994, 134, 203. [all data]

Belyaev, Gotkis, et al., 1990
Belyaev, V.N.; Gotkis, I.S.; Lebedeva, N.L.; Krasnov, K.S., Ionization potentials of MX molecules (M = Ca, Sr, Ba; X = F, Cl, Br, I, OH, O), Russ. J. Phys. Chem., 1990, 64, 773. [all data]

Farber, Srivastava, et al., 1987
Farber, M.; Srivastava, R.D.; Moyer, J.W.; Leeper, J.D., Effusion mass spectrometric determination of thermodynamic properties of the gaseous mono- and di-hydroxides of calcium and KCaO(g), J. Chem. Soc. Faraday Trans. 2, 1987, 83, 3229. [all data]

Murad, 1983
Murad, E., Abstraction reactions of Ca⁺ and Sr⁺ ions, J. Chem. Phys., 1983, 78, 6611. [all data]

Farber and Srivastava, 1976
Farber, M.; Srivastava, R.D., The dissociation energies of calcium oxide and strontium oxide, High Temp. Sci., 1976, 8, 73. [all data]

Drowart, Exsteen, et al., 1964
Drowart, J.; Exsteen, G.; Verhaegen, G., Mass spectrometric determination of the dissociation energy of the molecules MgO, CaO, SrO and Sr₂O, J. Chem. Soc. Faraday Trans., 1964, 60, 1920. [all data]

Brewer and Wang, 1972
Brewer, L.; Wang, J.L.-F., Ground state of gaseous CaO; a study of the matrix spectra of Ca and CaO, J. Chem. Phys., 1972, 56, 4305. [all data]

Lejeune, 1945
Lejeune, J.-M., Application de la methode d'explosion de fils minces a l'etude du spectre de CaO, Bull. Soc. R. Sci. Liege, 1945, 14, 318. [all data]

Gaydon, 1955
Gaydon, A.G., Green and orange band spectra of CaOH, CaOD and calcium oxide, Proc. R. Soc. London A, 1955, 231, 437. [all data]

Volnyets, Kovalenok, et al., 1974
Volnyets, G.A.; Kovalenok, G.V.; Sokolov, V.A., Rotational structure of the 5472-5463 Å band of calcium oxide, Opt. Spectrosc. Engl. Transl., 1974, 36, 609, In original 1034. [all data]

Veits and Gurvich, 1967
Veits, I.V.; Gurvich, L.V., Investigation of the absorption spectra of molecules of difficulty volatile substances and radicals in shock waves, Dokl. Chem. Engl. Transl., 1967, 173, 377, In original 1325. [all data]

Lagerqvist, 1954
Lagerqvist, A., Ultra-violet and blue bands of calcium oxide, Ark. Fys., 1954, 8, 83. [all data]

Brewer and Hauge, 1968
Brewer, L.; Hauge, R., Near infrared bands of diatomic CaO and SrO, J. Mol. Spectrosc., 1968, 25, 330. [all data]

Field, 1974
Field, R.W., Assignment of the lowest ³Π and ¹Π states of CaO, SrO, and BaO, J. Chem. Phys., 1974, 60, 2400. [all data]

Lejeune and Rosen, 1945
Lejeune, J.-M.; Rosen, B., Contribution a l'etude du spectre de CaO, Bull. Soc. R. Sci. Liege, 1945, 14, 322. [all data]

Hultin and Lagerqvist, 1951
Hultin, M.; Lagerqvist, A., An infra-red band-system of calcium oxide, Ark. Fys., 1951, 2, 471. [all data]

Ault and Andrews, 1975
Ault, B.S.; Andrews, L., Nitrogen matrix reactions of alkaline earth metal atoms with ozone: infrared spectra of the alkaline earth metal oxide molecules, J. Chem. Phys., 1975, 62, 2320. [all data]

Carlson, Kaiser, et al., 1970
Carlson, K.D.; Kaiser, K.; Moser, C.; Wahl, A.C., Electronic structure and low-lying triplet states of CaO, J. Chem. Phys., 1970, 52, 4678. [all data]

Yoshimine, 1968
Yoshimine, Y., Computed ground state properties of BeO, MgO, CaO, and SrO in molecular orbital approximation, J. Phys. Soc. Jpn., 1968, 25, 1100. [all data]

Engelke, Sander, et al., 1976
Engelke, F.; Sander, R.K.; Zare, R.N., Crossed-beam chemiluminescent studies of alkaline earth atoms with ClO₂, J. Chem. Phys., 1976, 65, 1146. [all data]

Colin, Goldfinger, et al., 1964
Colin, R.; Goldfinger, P.; Jeunehomme, M., Mass-spectrometric studies of vaporization of the sulphides of calcium, strontium and barium. The dissociation energy of S₂ and SO, Trans. Faraday Soc., 1964, 60, 306. [all data]

Kalff and Alkemade, 1973
Kalff, P.J.; Alkemade, C.T.J., Determination of dissociation energies for some alkaline earth (hydro-) oxides in CO/N₂O flames, J. Chem. Phys., 1973, 59, 2572. [all data]

Notes

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Symbols used in this document:

IE (evaluated)	Recommended ionization energy
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
S°_{liquid,1 bar}	Entropy of liquid at standard conditions (1 bar)
S°_solid	Entropy of solid at standard conditions
S°_{solid,1 bar}	Entropy of solid at standard conditions (1 bar)
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_fH°_liquid	Enthalpy of formation of liquid at standard conditions
Δ_fH°_solid	Enthalpy of formation of solid at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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