Best thing I can suggest is to first quit the app, then delete it, then reset your iPad and finally reinstall it from the App Store.
1. Go to the Home screen and double click the Home button. That will reveal the row of recently used apps at the bottom of the screen. Tap and hold on the app in question until it wiggles and displays a minus sign. Tap the minus sign to actually quit the app. Then tap anywhere on the screen above that bottom row to return the screen to normal. Then restart the app and see if it works normally.
2. To delete an app tap and hold on the app until it jiggles and displays an X. Tap the X and confirm that you want to delete the app. Then click the .home button to return your screen to normal.
3. To reset your device. Press and hold the Home and Sleep buttons simultaneously ignoring the red slider should one appear until the Apple logo appears. Let go of the buttons and let the device restart.
4. Start the App Store app and find Facebook. Download it to your iPad.
Hopefully this corrects your problem.