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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 ...
The Avogadro constant, commonly denoted N A [1] or L, [2] is an SI defining constant with an exact value of 6.022 140 76 × 10 23 mol −1 (reciprocal moles). [3] [4] It is this defined number of constituent particles (usually molecules, atoms, ions, or ion pairs—in general, entities) per mole and used as a normalization factor in relating the amount of substance, n(X), in a sample of a ...
Element Origin of name [1] [2] Group Period Block Standard atomic weight A r °(E) [a] Density [b] [c] Melting point [d] Boiling point [e] Specific heat capacity [f ...
The relative activity of a species i, denoted a i, is defined [4] [5] as: = where μ i is the (molar) chemical potential of the species i under the conditions of interest, μ o i is the (molar) chemical potential of that species under some defined set of standard conditions, R is the gas constant, T is the thermodynamic temperature and e is the exponential constant.
In chemistry, the mole fraction or molar fraction, also called mole proportion or molar proportion, is a quantity defined as the ratio between the amount of a constituent substance, n i (expressed in unit of moles, symbol mol), and the total amount of all constituents in a mixture, n tot (also expressed in moles): [1]
The molar ratio allows for conversion between moles of one substance and moles of another. For example, in the reaction 2 CH 3 OH + 3 O 2 → 2 CO 2 + 4 H 2 O. the amount of water that will be produced by the combustion of 0.27 moles of CH 3 OH is obtained using the molar ratio between CH 3 OH and H 2 O of 2 to 4.
The first of these quantities is used in atomic physics, the second in chemistry, but both refer to the same basic property of the element. To convert from "value of ionization energy" to the corresponding "value of molar ionization energy", the conversion is: 1 eV = 96.48534 kJ/mol 1 kJ/mol = 0.0103642688 eV [12]
Many elements can combine to form heteronuclear diatomic molecules, depending on temperature and pressure. Examples are gases carbon monoxide (CO), nitric oxide (NO), and hydrogen chloride (HCl). Many 1:1 binary compounds are not normally considered diatomic because they are polymeric at room temperature, but they form diatomic molecules when ...