There are two types of "science guns" in UR: energy (laser and plasma) and chemical. Both are viable, but if it's your first playthrough and you're struggling, I'd recommend normal difficulty.
Generally I don't recommend powergaming builds with 3 constitution for a first playthrough, so this character sacrifices agility to get a few more hps. But you could go with 3 con and 9 per, and raise agility to 6 to pick up sprint instead.
str 3, dex 9, agi 3, con 5, per 10, int 7
I'd increase per to 12 on level ups and the rest in dex, goes for both the chemist and the physicist. The difference is in feats and crafting skills.
1. aimed shot, nimble
2. opportunist
4. grenadier
At this point you can start picking up the 'science' feats for your guy: crooked shot and mad chemist or high technicalities and practical physicist (and then much later critical power) depending on what type of guns you want to use.
Skills: guns, throwing (or traps if you prefer; you can replace grenadier with trap expert & quick tinkering then), stealth, hacking, lockpicking, crafting and mercantile.
Regarding crafting skills, you can check the wiki requirements for weapons & grenades. Imo with the chemist it's worth to raise chemistry asap to craft at least mkiii - mkiv frag grenades (or traps), because they make a lot of the early game encounters (including depot a) much easier. The physicist can steal an energy weapon in junkyard, as part of the scrappers questline, so getting high electronics isn't as importantat this point.
