The number of extranuclear electrons in (1)Fe is 26, the extranuclear electron configuration of the ground state atom is 1s 22 p 63s 23 p 63d 64s 2, the symbol of the highest energy layer occupied by electrons is n, the number of atomic orbitals in the energy layer is 1+3+5+7= 16, and the number of electrons. The first ionization energy of the same periodic element increases from left to right, but the 2p level of the atom of N element is in a semi-complete stable state with low energy, and the first ionization energy is higher than that of the adjacent periodic element, so the first ionization energy O < n < f, so the answer is: n; 16; ? 2; o、N、F；

(2)(CN)2 is a linear molecule with symmetry, and the structural formula is: N≡C-C≡N, the number ratio of π bonds to σ bonds in (CN)2 is 4: 3, CN- is linear, and the hybridization mode of carbon atoms is sp, so the answer is 4: 3; sp；

(3) There is an ionic bond between potassium ion and hexacyanogen iron ion, and Fe2+ in hexacyanogen iron ion [Fe(CN)6]4- forms a coordination bond with CN-, and there are three C≡N bonds in CN-, which are polar * * * valence bonds, but there is no nonpolar * * * valence bond, so C is selected;

(4) Particles with the same number of total atoms and valence electrons are isoelectrons, molecules with the same number of SCN- electrons are CS2 or CO2, and the valence electron logarithm of the central atom is 4+02=2, so the molecular space configuration is linear, so the answer is: CS2 or CO2; Linear;

(5) The number of F- ions in the crystal cell = 12× 14=3, the number of Mg2+ ions =8× 18= 1, and the number of K+ ions = 1, so the chemical formula of the crystal is KMg. 3 120ρNA；