Thunderbolt

You conjure lightning that arcs in your hand. While concentrating on the spell you can make a ranged spell attack against a creature in a straight line, within 30 feet of you. On a hit, the target takes 1d10 lightning damage. The spell ends if you use your action to do anything else. The lightning arcing in your hand occasionally creates a thunderous boom. On a natural 20, add an additional 1d6 thunder damage. This damage type also increase per spell level casted. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the initial damage increases by 1d10 for each slot level above 1st.