Atoms are a form of currency in Fallout 76. They can be used in the Atomic shop to purchase different items for your character and profile in the game. Atoms can be used to purchase things like new character outfits, Pip Boy Skins, C.A.M.P. items, face paint, tattoos, poses and frames for photomode, custom emotes, and icons for your profile. You can get atoms in Fallout 76 by performing challenges in the game.
There are numerous challenges in Fallout 76. These include things like Daily and Weekly challenges which task you with completing different actions in the game. To see current challenges just head into the main menu of the game by pressing the start button to pull up the map and then pressing LB/L1 to open the menu. From there scroll down to challenges to see what ones are available for you.
Each challenge will give you a different amount of Atoms which appears to be how difficult a challenge is. Alongside the daily and weekly challenges you can do things like character challenges, survival challenges, combat challenges, social challenges, and world challenges. Each will give you a different number of atoms once you’ve completed it. You can see how much each challenge gives you on the right of the challenge list.
Of course, if you don’t want to do these challenges you can always purchase the Atom currency as well. Atoms are sold in bundles that range from $4.99 for 500 Atoms to $39.99 for 5000 Atoms. The money doesn’t go that far, however. Many items in the Atomic Shop cost around 1000 Atoms. $40 would just get you a few pieces of cosmetic items that have no impact on the gameplay.