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Characteristics Classification Calcium is a very ductile silvery metal sometimes described as pale yellow whose properties are very similar to the heavier elements in its group, strontiumbariumand radium.
A calcium atom has twenty electrons, arranged in the electron configuration [Ar]4s2. Like the other elements placed in group 2 of the periodic table, calcium has two valence electrons in the outermost s-orbital, which are very easily lost in chemical reactions to form a dipositive ion with the stable electron configuration of a noble gasin this case argon.
Hence, calcium is almost always divalent in its compounds, which are usually ionic. Hypothetical univalent salts of calcium would be stable with respect to their elements, but not to disproportionation to Ca for english divalent salts and calcium metal, because the enthalpy of formation of MX2 is much higher than those of the hypothetical MX.
Nevertheless, beryllium and magnesium are significantly different from the other members of the group in their physical and chemical behaviour: Its density of 1.
While calcium is a poorer conductor of electricity than copper or aluminium by volume, it is a better conductor by mass than both due to its very low density. The chemistry of calcium is that of a typical heavy alkaline earth metal. For example, calcium spontaneously reacts with water more quickly than magnesium and less quickly than strontium to produce calcium hydroxide and hydrogen gas.
It also reacts with the oxygen and nitrogen in the air to form a mixture of calcium oxide and calcium nitride. In bulk, calcium is less reactive: In the absence of steric hindrancesmaller group 2 cations tend to form stronger complexes, but when large polydentate macrocycles are involved the trend is reversed.
Most of these compounds can only be prepared at low temperatures; bulky ligands tend to favor stability.
For example, calcium di cyclopentadienylCa C5H5 2, must be made by directly reacting calcium metal with mercurocene or cyclopentadiene itself; replacing the C5H5 ligand with the bulkier C5 CH3 5 ligand on the other hand increases the compound's solubility, volatility, and kinetic stability.
Isotopes of calcium Natural calcium is a mixture of five stable isotopes 40Ca, 42Ca, 43Ca, 44Ca, and 46Ca and one isotope with a half-life so long that it can be considered stable for all practical purposes 48Cawith a half-life of about 4.
Calcium is the first lightest element to have six naturally occurring isotopes. It is produced in the silicon-burning process from fusion of alpha particles and is the heaviest stable nuclide with equal proton and neutron numbers; its occurrence is also supplemented slowly by the decay of primordial 40K.
Adding another alpha particle would lead to unstable 44Ti, which quickly decays via two successive electron captures to stable 44Ca; this makes up 2. The four lighter isotopes are mainly products of the oxygen-burning and silicon-burning processes, leaving the two heavier ones to be produced via neutron-capturing processes.
Although extremely neutron-rich for such a light element, 48Ca is very stable because it is a doubly magic nucleushaving 20 protons and 28 neutrons arranged in closed shells. Its beta decay to 48 Sc is very hindered because of the gross mismatch of nuclear spin: While two excited states of 48Sc are available for decay as well, they are also forbidden due to their high spins.
As a result, when 48Ca does decay, it does so by double beta decay to 48 Ti instead, being the lightest nuclide known to undergo double beta decay. Calcium is the only element to have two primordial doubly magic isotopes.
The experimental lower limits for the half-lives of 40Ca and 46Ca are 5. It decays by electron capture to stable 41 K with a half-life of about a hundred thousand years. Its existence in the early Solar System as an extinct radionuclide has been inferred from excesses of 41K: The isotopes lighter than 42Ca usually undergo beta plus decay to isotopes of potassium, and those heavier than 44Ca usually undergo beta minus decay to isotopes of scandiumalthough near the nuclear drip lines proton emission and neutron emission begin to be significant decay modes as well.
Lighter isotopes are preferentially incorporated into these minerals, leaving the surrounding solution enriched in heavier isotopes at a magnitude of roughly 0. The climate of present-day Italy being warmer than that of Egypt, the ancient Romans instead used lime mortars made by heating limestone CaCO3 ; the name "calcium" itself derives from the Latin word calx "lime".
In his table of the elements, Lavoisier listed five "salifiable earths" i. About these "elements", Lavoisier speculated: We are probably only acquainted as yet with a part of the metallic substances existing in nature, as all those which have a stronger affinity to oxygen than carbon possesses, are incapable, hitherto, of being reduced to a metallic state, and consequently, being only presented to our observation under the form of oxyds, are confounded with earths.
It is extremely probable that barytes, which we have just now arranged with earths, is in this situation; for in many experiments it exhibits properties nearly approaching to those of metallic bodies.
It is even possible that all the substances we call earths may be only metallic oxyds, irreducible by any hitherto known process. Electrolysis then gave calcium—mercury and magnesium—mercury amalgams, and distilling off the mercury gave the metal. Minerals of the first type include limestonedolomitemarblechalkand iceland spar ; aragonite beds make up the Bahamasthe Florida Keysand the Red Sea basins.When the English–Language Arts Content Standards for California Public Schools, Kindergarten Through Grade Twelve was adopted by the California State Board of Education on November 14, , the members of the State Board were the following: Yvonne W.
Larsen, President; Jerry Hume. Calcium is a chemical element with symbol Ca and atomic number An alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to grupobittia.com physical and chemical properties are most similar to its heavier homologues strontium and grupobittia.com is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium.
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California English (or Californian English) collectively refers to American English in California, particularly an emerging youthful variety, mostly associated with speakers of urban and coastal California. California Education Code (EC) Section requires the State Board of Education to approve standards for English language development (ELD) for pupils whose primary language is a language other than English.
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