Athesm or Atheism: How To spell?

The word Athesm is misspelled against Atheism, meaning "The denial of the existence of God."

Word contains consecutive vowels 'EI' in between alphabets ath & sm is misspelled as 'E' as letter 'I' is phonetically ignored
Wrong Spelling:  ath-e-sm 
Correct Spelling:  ath-ei-sm 
Explore spell check of Atheism to spell without errors.