Ode to the letter ‘k’

Physics and Chemistry both owe a debt
To one letter they use in great excess.
Without this key symbol, I cannot stress,
The laws of nature wouldn't seem correct,
Lecture theatres' boards would be bereft,
All planar wave solutions dispossessed,
Without the glyph whose presence we are blessed:
Eleventh letter of the alphabet!

Potassium's shorthand is written thus,
And likewise called are first electron shells,
Dispersion-like relations we survey,
Boltzmann's constant we write down and discuss,
With S.I unit temperatures, as well!
All that, and more, thanks to the letter 'k'!