How to politely and logically explain that I don't want to receive notification at my private social media account? My department is becoming more and more annoying by posting everything in Facebook group, from exam results, seminar schedule, to private information about students ( telephone numbers, addresses, emails, etc.)

I don't know how to explain them  that I care about safety of personal information and that privacy of my personal information are important to me, but please be aware that I don't want to sound pretentious. Is there any way to address this issue correctly?
I agree with Captain Emacs that you have a right to privacy. Private information(exam scores, contact information) should not be posted on Facebook but general seminar schedules can be.

I think the best course of action is to discuss this with the head of the department, and request in writing, that your information not be posted there. If that doesn't work then you will have to speak to someone above the him/her. If this is not an option see if there is someone you trust that you can ask for their help or advice to bring this issue to the right person's attention.