Ministry of Defence Main Building (United Kingdom) each and cost £12,600. Similar figures representing "air" and "fire" were intended to be installed at the south end of the building, however these were never constructed. During the 1950s, building staff nicknamed the statues "Mr and Mrs Parkinson", after Cyril Northcote Parkinson, the Board of Trade civil servant who devised Parkinson's Law which states "work expands so as to fill the time available for its completion". More recently MOD staff refer to the statues as the "two fat ladies". The badge of the RAF is carved into stone columns either side of the southern entrance to the building, reflecting
Aufbau principle building-up principle or the aufbau rule. The details of this "building-up" tendency are described mathematically by atomic orbital functions. Electron behavior is elaborated by other principles of atomic physics, such as Hund's rule and the Pauli exclusion principle. Hund's rule asserts that even if multiple orbitals of the same energy are available, electrons fill unoccupied orbitals first, before reusing orbitals occupied by other electrons. But, according to the Pauli exclusion principle, in order for electrons to occupy the same orbital, they must have different spins (−1/2 and 1/2). As we pass from one element to another of next higher atomic