The word radioisotope is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 16
Highest Scoring Words With Friends™ Plays In The Letters
Seven Letter Word Alert: (82 words)
adipose, adopter, airiest, airside, aridest, aspired, astride, astroid, dairies, departs, deports, deposit, despair, diapers, diaries, diarist, diopter, dioptre, diorite, dirties, disrate, disroot, ditsier, dopiest, editors, iodiser, iodites, irisate, isotope, oospore, opiated, opiates, opioids, optrode, osteoid, parotid, parties, pastier, peridot, periods, petards, piarist, pirated, pirates, pitiers, poorest, posited, praised, readopt, riptide, roadies, roasted, roisted, roosted, ropiest, seaport, soapier, sootier, sortied, spiroid, spirted, spoored, sported, steroid, stooped, stooper, storied, striped, tapirid, tiderip, tidiers, tierods, tipsier, tirades, topside, toroids, torpedo, torpids, traipse, tripeds, tripods, trooped