periodic system

15 LETTERS · STARTS WITH P

periodic system is a valid 15-letter word worth 24 points in Scrabble and 26 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

P3E1R1I1O1D2I1C3S1Y4S1T1E1M3

3 + 1 + 1 + 1 + 1 + 2 + 1 + 3 + 0 + 1 + 4 + 1 + 1 + 1 + 3 =24 PTS

DOUBLE WORD → 48TRIPLE WORD → 72

MEANING

What does periodic system mean?