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There are currently 118 known chemical elements with a wide range of physical and chemical properties. Amongst this diversity, scientists have found it useful to apply names for various sets of elements that have similar properties, to varying degrees. Many of these sets are formally recognized by the standards body IUPAC. [1]
The similarity-based [4] virtual screening (a kind of ligand-based virtual screening) assumes that all compounds in a database that are similar to a query compound have similar biological activity. Although this hypothesis is not always valid, [5] quite often the set of retrieved compounds is considerably enriched with actives. [6]
A homologue (also spelled as homolog) is a compound belonging to a homologous series. [1] Compounds within a homologous series typically have a fixed set of functional groups that gives them similar chemical and physical properties. (For example, the series of primary straight-chained alcohols has a hydroxyl at the end of the carbon chain ...
Arranged this way, elements in the same group (column) have similar chemical and physical properties, reflecting the periodic law. For example, the halogens lie in the second-to-last group ( group 17 ) and share similar properties, such as high reactivity and the tendency to gain one electron to arrive at a noble-gas electronic configuration.
The elements have very similar properties: they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure. [ 2 ] Together with helium , these elements have in common an outer s orbital which is full [ 2 ] [ 3 ] [ 4 ] —that is, this orbital contains its full complement of two electrons, which the alkaline ...
The first two members of the group share similar properties as they are solid metals under standard conditions. Mercury is the only metal that is known to be a liquid at room temperature – as copernicium's boiling point has not yet been measured accurately enough, [ note 2 ] it is not yet known whether it is a liquid or a gas under standard ...
Thus, on both descending a period and crossing a group by one element, the changes "cancel" each other out, and elements with similar properties which have similar chemistry are often found – the atomic radius, electronegativity, properties of compounds (and so forth) of the diagonal members are similar.
The lighter three Group 5 elements occur naturally and share similar properties; all three are hard refractory metals under standard conditions. The fourth element, dubnium , has been synthesized in laboratories, but it has not been found occurring in nature, with half-life of the most stable isotope, dubnium-268, being only 16 hours, and other ...