Atom can be downloaded and used for free for 14 days. All that is required is you to enter your credit card details, which will not be charged for 14 days. 

If you cancel your purchase within the first 14 days of getting an Atom license then your credit card will not be charged at all. 

If you do not cancel within 14 days than your credit card will be billed for the amount outlined in your payment method ($139 for a full purchase, or $9 a month for 16 months if set up with the payment plan unless you signed up through a bundle or other promotion).