Since there are a lot of compound finals in Chinese, we have categorized them into different groups for clarity, as illustrated in the table:
ai, ei, ao, ou
an, en, ang, eng, ong
ia, iao, ie, iou (iu), ian, in, iang, ing, iong
The "o" in “iou” is especially conspicuous in third- and fourth- tone syllables.
For producing the sound "ian", keep your mouth a bit more closed and your tongue higher than when you say the simple final "a".
When pronouncing the "i" in the final "iong" make sure to round your lips because of the "ong".
ua, uo, uai, uei (ui), uan, uen (un), uang, ueng
The "e" in "uei" is especially conspicuous in third- and fourth- tone syllables.
üe, üan, ün
er
"er" with a first tone does not exist in Mandarin. The pronunciation of "er" will be affected by the tones, and the mouth is wider when it is pronounced in the fourth tone.