How many potassium atoms are present in 8.90 grams of potassium oxide

Joan writes four numbers on the board in standard form, and then she writes their scientific notation

When water dissociates, each water molecule splits into a hydroxide ion and a) h 3 o + b) a hydrogen atom c) a hydrogen ion d) h 2 o e) oh —

What type of electromagnetic waves does the human eye see as the colors red blue or green a visible light waves b radio waves c infrared waves d microwaves