Sodium condensed electron configuration

The condensed electron configuration for a nitrogen atom, for example, is [He]2s 2p. The notation [He] is used to represent Is. For a sodium atom [Z = 11), the condensed electron configuration is [Ne]3s. Here, [Ne] represents, ls 2s 2p . Be aware that condensed electron configurations are simply convenient short forms. Thus, [Ne]3s does not mean that a sodium atom is the same as a neon atom plus one electron. Sodium and neon are different elements because the nuclei of their atoms are completely different. 

In Group IA(1), lithium and sodium have the condensed electron configuration [noble gas] ns (where n is the quantum number of the outermost energy level), as do all the other alkali metals (K, Rb, Cs, Fr). All are highly reactive metals that form ionic compounds with nonmetals with formulas such as MCI, M2O, and M2S (where M represents the alkali metal), and all react vigorously with water to displace H2. 

We can generalize what we have just done for the electron configuration of sodium. In writing the condensed electron configuration of an element, the electron configuration of the nearest noble-gas element of lower atomic number is represented by its chemical symbol in brackets. For lithium, for example, we write... 

We refer to the electrons represented by the bracketed symbol as the noble-gas core of the atom. More usually, these inner-shell electrons are referred to as the core electrons. The electrons given after the noble-gas core are called the outer-shell elearons. The outer-shell electrons include the electrons involved in chemical bonding, which are called the valence electrons. For the elements with atomic number of 30 or less, all of the outer-shell electrons are valence electrons. By comparing the condensed electron configurations of lithium and sodium, we can appreciate why these two elements are so... 

Perhaps the most useful part of the reported synthesis is the facile preparation of (—)-pyrimidoblamic acid (12 Scheme 3). A key to this synthesis is the preparation of the fully substituted pyrimidine 8. This was done by a one-pot inverse electron demand Diels-Alder reaction between the symmetrical triazine 7 and prop-1-ene-1,1-diamine hydrochloride, followed by loss of ammonia, tautomerization, and loss of ethyl cyanoformate through a retro-Diels-Alder reaction. Selective low-temperature reduction of the more electrophilic C2 ester using sodium borohydride afforded 9, the aldehyde derivative of which was condensed with 7V -Boc-protected (3-aminoalaninamide to give the imine 10. Addition of the optically active A-acyloxazolidinone as its stannous Z-enolate provided almost exclusively the desired anti-addition product 11, which was converted into (—)-pyrimidoblamic acid (12). Importantly, this synthesis confirmed Umezawa s assignment of absolute configuration at the benzylic center. 

A condensed ground state configuration for sodium can be written using [Ne] to represent the first 10 electrons of sodium that have the identical configuration as neon. 

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