[grey_whiskers]

IIRC, a proton is two up quarks and a down, a neutron is two down quarks and an up.

Up quarks have charge +2/3,and down quarks have charge -1/3.

So "two ups and a down" yield +2/3 + 2/3 - 1/3 = +1
and
"two downs and an up " yield -1/3 -1/3 + 2/3 = 0

Cheers!

[The Comedian]

The only physics joke I ever invented:

0: Knock knock.

1: Who's there?

0: Heisenberg.

1: Heisenberg who?

0: I'm uncertain.

(rimshot)

Tip your waitress. Good night.

Frowning takes 68 muscles.
Smiling takes 6.
Pulling this trigger takes 2.
I'm lazy.