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Appearance | dull gray, silver; with a pale yellow tint[1] |
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| 40.078(4)[2] |
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Group | group 2 (alkaline earth metals) |
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Period | period 4 |
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Block | s-block |
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Electron configuration | [Ar] 4s2 |
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Electrons per shell | 2, 8, 8, 2 |
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Phase at STP | solid |
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Melting point | 1115 K (842 °C, 1548 °F) |
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Boiling point | 1757 K (1484 °C, 2703 °F) |
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Density (near r.t.) | 1.55 g/cm3 |
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when liquid (at m.p.) | 1.378 g/cm3 |
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Heat of fusion | 8.54 kJ/mol |
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Heat of vaporization | 154.7 kJ/mol |
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Molar heat capacity | 25.929 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
864 |
956 |
1071 |
1227 |
1443 |
1755 |
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Oxidation states | +1,[3] +2 (a strongly basic oxide) |
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Electronegativity | Pauling scale: 1.00 |
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Ionization energies | - 1st: 589.8 kJ/mol
- 2nd: 1145.4 kJ/mol
- 3rd: 4912.4 kJ/mol
- (more)
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Atomic radius | empirical: 197 pm |
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Covalent radius | 176±10 pm |
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Van der Waals radius | 231 pm |
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Spectral lines of calcium |
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Natural occurrence | primordial |
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Crystal structure | face-centered cubic (fcc) |
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Speed of sound thin rod | 3810 m/s (at 20 °C) |
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Thermal expansion | 22.3 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 201 W/(m⋅K) |
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Electrical resistivity | 33.6 nΩ⋅m (at 20 °C) |
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Magnetic ordering | diamagnetic |
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Molar magnetic susceptibility | +40.0·10−6 cm3/mol[4] |
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Young's modulus | 20 GPa |
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Shear modulus | 7.4 GPa |
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Bulk modulus | 17 GPa |
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Poisson ratio | 0.31 |
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Mohs hardness | 1.75 |
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Brinell hardness | 170–416 MPa |
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CAS Number | 7440-70-2 |
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Discovery and first isolation | Humphry Davy (1808) |
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Main isotopes[5] |
Decay |
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abundance |
half-life (t1/2) |
mode |
product |
40Ca |
96.9% |
stable |
41Ca |
trace |
9.94×104 y |
ε |
41K |
42Ca |
0.647% |
stable |
43Ca |
0.135% |
stable |
44Ca |
2.09% |
stable |
45Ca |
synth |
163 d |
β− |
45Sc |
46Ca |
0.004% |
stable |
47Ca |
synth |
4.5 d |
β− |
47Sc |
48Ca |
0.187% |
6.4×1019 y |
β−β− |
48Ti |
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Category: Calcium | references |