Electron structure for elements

Table 3.3 gives electronic structures for elements with atomic numbers 1-20. 

Table 3.3 The electronic structure for elements with atomic numbers 1-20. The last column will be filled in later on in this unit ...

Bohr also attempted to write electronic structures (in terms of orbits) for elements up to chromium. However, the theoretical treatment of multi-electron systems proved to be very complex, and Bohr assigned electronic structures for elements principally on the basis of chemical properties. Thus lithium was assigned a structure of (2,1) but nitrogen was presumed to be (4,3) because of its trivalency. Over the next few years, Bohr, along with Arnold Sommerfeld (1868-1951), William Wilson and Charles Bury, refined electronic structures on the basis of both spectral and chemical behaviour. 

---