cChemistry

i I wish i I could invent a new chemical substance.

Watch out for capitalization. Proper nouns (such as "I" or somebody's name) need to be capitalized. So do words are the beginning of a sentence and words in titles except for little linking words like "and" or "to." 

So, what kind of chemical substance do you want to invent?

chemistry

I wish i could invent a new chemical substance.

Chemistry

i wish i could invent a new chemical substance.