--------------------------------------------------------------------------------
251. xenon trioxide
276. NBr3
252. gold(I) chloride
277. Cl2O3
253. gold(I) cyanide
278. CsF
254. sodium oxide
279. CO
255. potassium chlorate
280. Cu2S
256. mercurous nitrite
281. KHCO3
257. nickel(II) fluoride
282. SbCl5
258. potassium cyanide
283. CO2
259. manganese dioxide
284. HgO
260. osmium tetrachloride
285. PCl3
261. rubidium carbonate
286. PBr5
262. trisulfur dinitride
287. IF7
263. nitrogen trichloride
288. Cl2O
264. vanadium(V) oxide
289. CCl4
265. selenium tetrafluoride
290. XeF4
266. stannous hypochlorite
291. Hg(OH)2
267. tellurium hexafluoride
292. CaH2
268. lanthanum(III) phosphate
293. As4O6
269. sodium hydrogen sulfate monohydrate
294. BN
270. chromium(III) hydrogen phosphate
295. CoS
271. NaOH
296. N2O4
272. NI3
297. H3BO3
273. ClF3
298. I2O5
274. P3N5
299. PbO
275. UF6
300. NaBr