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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 ...
This is a list of chemical elements and their atomic properties, ordered by atomic number (Z). Since valence electrons are not clearly defined for the d-block and f-block elements, there not being a clear point at which further ionisation becomes unprofitable, a purely formal definition as number of electrons in the outermost shell has been used.
Disodium hydrogen arsenate is highly toxic. The salt is the conjugate base of arsenic acid. It is a white, water-soluble solid. [1] Being a diprotic acid, its acid-base properties is described by two equilibria: H 2 AsO − 4 + H 2 O ⇌ HAsO 2− 4 + H 3 O + (pK a2 = 6.94) HAsO 2− 4 + H 2 O ⇌ AsO 3− 4 + H 3 O + (pK a3 = 11.5)
The molar mass of atoms of an element is given by the relative atomic mass of the element multiplied by the molar mass constant, M u ≈ 1.000 000 × 10 −3 kg/mol ≈ 1 g/mol. For normal samples from Earth with typical isotope composition, the atomic weight can be approximated by the standard atomic weight [ 2 ] or the conventional atomic weight.
Phosphorous acid (or phosphonic acid) is the compound described by the formula H 3 PO 3. This acid is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula. Phosphorous acid is an intermediate in the preparation of other phosphorus compounds.
The systematic IUPAC name is not always the preferred IUPAC name, for example, lactic acid is a common, and also the preferred, name for what systematic rules call 2-hydroxypropanoic acid. This list is ordered by the number of carbon atoms in a carboxylic acid.
The following molar volumes and densities for the majority of the gaseous elements were calculated from the van der Waals equation of state, using the quoted values of the van der Waals constants. The source for the van der Waals constants and for the literature densities was: R. C. Weast (Ed.), Handbook of Chemistry and Physics (53rd Edn ...
Selenous acid is analogous to sulfurous acid, but it is more readily isolated. Selenous acid is easily formed upon the addition of selenium dioxide to water. As a crystalline solid, the compound can be seen as pyramidal molecules that are interconnected with hydrogen bonds. In solution it is a diprotic acid: [3] H 2 SeO 3 ⇌ H + + HSeO − 3 ...