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The form of the periodic table is closely related to the atomic electron configuration for each element. For example, all the elements of group 2 (the table's second column) have an electron configuration of [E] n s 2 (where [E] is a noble gas configuration), and have notable similarities in their chemical properties.
The p-block elements show variable oxidation states usually differing by multiples of two. The reactivity of elements in a group generally decreases downwards. (Helium breaks this trend in group 18 by being more reactive than neon, but since helium is actually an s-block element, the p-block portion of the trend remains intact.)
Lone pairs can contribute to a molecule's dipole moment. NH 3 has a dipole moment of 1.42 D. As the electronegativity of nitrogen (3.04) is greater than that of hydrogen (2.2) the result is that the N-H bonds are polar with a net negative charge on the nitrogen atom and a smaller net positive charge on the hydrogen atoms.
The form with the f-block included in the main body is sometimes called the 32-column [6] or long form; [33] the form with the f-block cut out the 18-column [6] or medium-long form. [33] The 32-column form has the advantage of showing all elements in their correct sequence, but it has the disadvantage of requiring more space. [34]
As 5 > 3, it leaves two unused electrons in a lone pair unless there is a positive charge around (like in [NH 4] +). When a pnictogen forms only three single bonds, effects of the lone pair typically results in trigonal pyramidal molecular geometry.
In mathematics, the linear span (also called the linear hull [1] or just span) of a set of elements of a vector space is the smallest linear subspace of that contains . It is the set of all finite linear combinations of the elements of S , [ 2 ] and the intersection of all linear subspaces that contain S . {\displaystyle S.}
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Each element or molecule displays a characteristic set of spectral lines, such as the hydrogen spectral series. When detected, spectroscopic measurements of the strength and width of these lines allow the composition and physical properties of a substance to be determined. [166] [167]