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Natural calcium is a mixture of five stable isotopes (40 Ca, 42 Ca, 43 Ca, 44 Ca, and 46 Ca) and one isotope with a half-life so long that it is for all practical purposes stable (48 Ca, with a half-life of about 4.3 × 10 19 years). Calcium is the first (lightest) element to have six naturally occurring isotopes.
The Ca 2+ concentration of the vacuole may reach millimolar levels. The most striking use of Ca 2+ ions as a structural element in algae occurs in the marine coccolithophores, which use Ca 2+ to form the calcium carbonate plates, with which they are covered. Calcium is needed to form the pectin in the middle lamella of newly formed cells.
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Condensation forming in the low pressure zone above the wing of an aircraft due to adiabatic expansion. Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization.
A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.
The planets condensed from the solar nebula, and much of the details of their composition are determined by fractionation as they cooled. The phases that condense fall into five groups. First to condense are materials rich in refractory elements such as Ca and Al. These are followed by nickel and iron, then magnesium silicates.
Selenium, which is an essential element for animals and prokaryotes and is a beneficial element for many plants, is the least-common of all the elements essential to life. [ 3 ] [ 63 ] Selenium acts as the catalytic center of several antioxidant enzymes, such as glutathione peroxidase , [ 11 ] and plays a wide variety of other biological roles .
These elements originally referred to earth, water, air and fire rather than the chemical elements of modern science. The term 'elements' ( stoicheia ) was first used by Greek philosopher Plato around 360 BCE in his dialogue Timaeus , which includes a discussion of the composition of inorganic and organic bodies and is a speculative treatise on ...