peacefulness

noun

1. Lack of emotional agitation: calm, calmness, peace, placidity, placidness, quietude, serenity, tranquillity. See calm/agitation.
2. An absence of motion or disturbance: calm, calmness, hush, lull, peace, placidity, placidness, quiet, quietness, serenity, stillness, tranquillity, untroubledness. See calm/agitation.

The noun has 2 meanings:

Meaning #1: a state that is calm and tranquil
  Synonym: peaceableness

Meaning #2: the absence of mental stress or anxiety
  Synonyms: peace, peace of mind, repose, serenity, heartsease, ataraxis