I have submitted journal articles that come from my thesis.
When defending the thesis, is it a good idea to give the names of the journals to which those pertaining papers were submitted to?
No, when defending your thesis there is no reason to give the names of the journals to which you have submitted papers based on it. It would not benefit you in any way (since they have not been accepted) and you will be embarrassed if the papers are rejected.
From my experience of defending my own master thesis and supervision of some others, I can conclude that it is always a good idea to present the papers that you submitted based on content from your thesis (in the main contributions slide), pointing out the details of the conference/journal, even when they are, yet, under review (just point out that in the presentation).
In some case it may be helpful to have a preprint version attached to your thesis document or in some repository such as arXiv.