Kalsiyo

Calcium, ₂₀Ca

Calcium
Appearance	dull gray, silver; with a pale yellow tint
Standard atomic weight Ar°(Ca)
	40.078±0.004 40.078±0.004 (pinaikli)
Calcium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Mg ↑ Ca ↓ Sr potassium ← calcium → scandium
Atomic number (Z)	20
Group	2
Period	4
Block	s-block
Electron configuration	[Ar] 4s2
Electrons per shell	2, 8, 8, 2
Physical properties
Phase at STP	solido
Melting point	1115 K ​(842 °C, ​1548 °F)
Boiling point	1757 K ​(1484 °C, ​2703 °F)
Density (at 20° C)	1.526 g/cm3
when liquid (at m.p.)	1.378 g/cm3
Heat of fusion	8.54 kJ/mol
Heat of vaporization	154.7 kJ/mol
Molar heat capacity	25.929 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 864 956 1071 1227 1443 1755
Atomic properties
Oxidation states	+1, +2 (isang matapang na panimulang oksido)
Electronegativity	Pauling scale: 1.00
Ionization energies	1st: 589.8 kJ/mol 2nd: 1145.4 kJ/mol 3rd: 4912.4 kJ/mol (more)
Atomic radius	empirical: 197 pm
Covalent radius	176±10 pm
Van der Waals radius	231 pm
Mga linyang espektral ng calcium
Other properties
Natural occurrence	primordiyal
Crystal structure	​face-centered cubic (fcc) (cF4)
Lattice constant	a = 558.8 pm (at 20 °C)
Thermal expansion	22.27×10−6/K (at 20 °C)
Thermal conductivity	201 W/(m⋅K)
Electrical resistivity	33.6 nΩ⋅m (at 20 °C)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	+40.0×10−6 cm3/mol
Young's modulus	20 GPa
Shear modulus	7.4 GPa
Bulk modulus	17 GPa
Speed of sound thin rod	3810 m/s (at 20 °C)
Poisson ratio	0.31
Mohs hardness	1.75
Brinell hardness	170–416 MPa
CAS Number	7440-70-2
History
Discovery and first isolation	Humphry Davy (1808)
Isotopes of calcium
Main isotopes Decay 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

Ang kalsyo o kalsyum (Kastila: calcio, Ingles: calcium, may sagisag na Ca, atomikong bilang na 20, atomikong timbang na 40.08, punto ng pagkatunaw na mula 842 hanggang 48 °C, punto ng pagkulong 1,487 °C, espesipikong grabidad na 1.55, at V na 2) ay isang elementong metalikong kahawig ng pilak at medyo may katigasan. Isa ito sa mahahalagang sangkap sa mga buto, sa mga kabibe, at sa mga dahon. Sangkap din ito sa paggawa ng plaster, apog, at semento. Natuklasan ito noong 1808 ni Humphry Davy.