What is "Mizreh"?
Rashi: It is a sieve.
What is the meaning of "va'Ezrem ba'Mizreh"?
Radak: Just like one spreads grain in a sieve [to sift it], so I will spread them in the gates (cities) of the land. This refers to the 10 tribes that were exiled.
What are "Sha'arei ha'Aretz"?
Radak: [In the exile, I will spread them] in all cities of the land. It says Sha'arei, because one enters and leaves the city via the gate - "l'Chol Ba'ei Sha'ar Iro" (Bereishis 23:6). Here and elsewhere, Yonason translates Sha'arei to be cities.
To whom does "Shikalti Ibadti" refer?
Radak: It is the 10 tribes. Yehudah saw all this, and did not repent! It says Shikalti because they were His sons.
Malbim: I bereaved them of their minor children, and Ibadti (killed) the adults.