Chemistry Christmas Song

Quantum Chemistry
On the first day of Christmas, my professor gave to me: An exam in Quantum Chemistry. On the second day of Christmas, my professor gave to me: a double integral and an exam in Quantum Chemistry. On the third day of Christmas, my professor gave to me: three orbitals, a double integral, and an exam in Quantum Chemistry. On the fourth day of Christmas, my professor gave to me: four harmonic oscillators, three orbitals, etc. On the fifth day of Christmas, my professor gave to me: Five Hermitian Operators! Four harmonic ocillators, three orbitals, etc. On the sixth day of Christmas, my professor gave to me: six spin-orbit couplings, etc. On the seventh day of Christmas, my professor gave to me: seven basis functions, etc. On the eighth day of Christmas, my professor gave to me: eight time dependent perturbations, etc. On the ninth day of Christmas, my professor gave to me: nine Slater determinants, etc. On the tenth day of Christmas, my professor gave to me: ten electrons tunneling, etc. On the eleventh day of Christmas, my professor gave to me: eleven photons emitting, etc. On the twelfth day of Christmas, my professor gave to me: 12 fermions exchanging, etc. 

Math Lesson

Math Teacher: "Now suppose the number of sheep is x..."
Student: "Yes sir, but what happens if the number of sheep is not x?"