unbalanced vs unstable

unbalanced

adj
  • not balanced, without equilibrium; dizzy 

  • irrational or mentally deranged 

  • of an expression having different numbers of left and right parentheses 

  • not adjusted such that debit and credit correspond 

  • an offensive line with more players on one side of the center than on the other 

unstable

adj
  • Not stable. 

  • Readily decomposable. 

  • Radioactive, especially with a short half-life. 

  • Unpredictable. 

  • Fickle. 

  • Having a strong tendency to change. 

  • Fluctuating; not constant. 

verb
  • To release (an animal) from a stable. 

How often have the words unbalanced and unstable occurred in a corpus of books? (source: Google Ngram Viewer )