larger principal quantum shell no. >

shell further from nucleus, higher energy level of e^- in shell, e^- less tightly attracted to nucleus >

sub-shells in each PQS; s,p,d,f

orbitals(each 2e^-) in each sub-shell;

s; s -> spherical

p; p_x, p_y, p_z ->2 lobes along axis

d_xy, d_xz, d_yz, d_x²-y², d_z² -> xy,xz,yz; 4 lobes b/w axis, x²-y²; 4 lobes along axis, z²; 2 lobes along axis w/ ring @ centre

3d, 4s sub-shells close in energy;

empty, energy 4s<3d

filled, energy 3d e^- repel 4s e^- further from nucleus to higher energy level

Learn: H2 Chemistry 1 - Atomic structure