why alkali metals have low melting and boiling points
Alkali metal The physical and chemical properties of the alkali metals can be readily explained by their having an ns1 valence electron configuration, which results in weak metallic bonding. Hence, all the alkali metals are soft and have low densities,[5] melting[5] and boiling points,[5] as well as heats of sublimation, vaporisation, and dissociation.[6]:74 They all crystallise in the body-centered cubic crystal structure,[6]:73 and have distinctive flame colours because their outer s electron is very easily excited.[6]:75 The ns1 configuration also results in the alkali metals having very large atomic and ionic radii, as well as very high thermal and electrical conductivity.[6]:75 Their chemistry is dominated by the loss of their lone valence electron in the outermost s-orbital to form the +1 oxidation state, due to the ease of ionising this electron and the very high second ionisation energy.[6]:76 Most of the chemistry has been observed only for the first five members of the group. The chemistry of francium is not well established due to its extreme radioactivity;[5] thus, the presentation of its properties here is limited. What little is known about francium shows that it is very close in behaviour to caesium, as expected. The physical properties of francium are even sketchier because the bulk element has never been observed; hence any data that may be found in the literature are certainly speculative extrapolations.[7]
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Isoelectric point For an amino acid with only one amine and one carboxyl group, the pI can be calculated from the mean of the pKas of this molecule.[4]
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