The present participle of think is thinking. Present participles always end in -ing.
"Encouraged" is the simple past and past participle of the verb "encourage".
Becoming
choosing
he or she barks or it barks present particle of bark
electrons are not present in the nucleus
Lying around.
If you think to a beta particle the symbol is β.
If you mean subatomic particles, all of the standard ones are present.
Increased is the past tense of increase.
Present participle - doing. Past participle - done.
If you think to the boson Higgs this is not a small particle.
Fun isn't a verb, so it doesn't have a past or present participle.