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[1] Relatively more stable entities with unpaired electrons do exist, e.g. the nitric oxide molecule has one. According to Hund's rule, the spins of unpaired electrons are aligned parallel and this gives these molecules paramagnetic properties. The most stable examples of unpaired electrons are found on the atoms and ions of lanthanides and ...
For phosphorus (element 15) as an example, the concise form is [Ne] 3s 2 3p 3. Here [Ne] refers to the core electrons which are the same as for the element neon (Ne), the last noble gas before phosphorus in the periodic table. The valence electrons (here 3s 2 3p 3) are written explicitly for all atoms.
The other pnictides phosphorus, arsenic, antimony and bismuth also react with the lanthanide metals to form monopnictides, LnQ, where Q = P, As, Sb or Bi. Additionally a range of other compounds can be produced with varying stoichiometries, such as LnP 2, LnP 5, LnP 7, Ln 3 As, Ln 5 As 3 and LnAs 2. [66]
The most reactive kind of metallic element is an alkali metal of group 1 (e.g., sodium or potassium); this is because such an atom has only a single valence electron. During the formation of an ionic bond , which provides the necessary ionization energy , this one valence electron is easily lost to form a positive ion (cation) with a closed ...
Among the lanthanides, lanthanum is exceptional as it has no 4f electrons as a single gas-phase atom. Thus it is only very weakly paramagnetic, unlike the strongly paramagnetic later lanthanides (with the exceptions of the last two, ytterbium and lutetium, where the 4f shell is completely full). [20]
The valence is the combining capacity of an atom of a given element, determined by the number of hydrogen atoms that it combines with. In methane, carbon has a valence of 4; in ammonia, nitrogen has a valence of 3; in water, oxygen has a valence of 2; and in hydrogen chloride, chlorine has a valence of 1.
For transition metals, the number of valence electrons ranges from 3 to 12 (ns and (n−1)d orbitals). For lanthanides and actinides, the number of valence electrons ranges from 3 to 16 (ns, (n−2)f and (n−1)d orbitals). All other non-valence electrons for an atom of that element are considered core electrons.
Valence bond theory complements molecular orbital theory, which does not adhere to the valence bond idea that electron pairs are localized between two specific atoms in a molecule but that they are distributed in sets of molecular orbitals which can extend over the entire molecule. Although both theories describe chemical bonding, molecular ...