Hi forzabarcelona and Felipe!
"
Porque Ricardo não pode ir ao concerto."
In this case, "porque" (because) is
a conjunction with a relation which marks a reason, a cause and it´s used in affirmative sentences only or when you´re explaining something to someone.
Example: Eu não vou à escola porque está a chover. (I don´t go to school because it´s raining)
"
Porque é que or
Porquê Ricardo não pode ir ao concerto?"
These are the right
interrogative adverbs that you can use when asking something.
Example: Porque é que falas tão alto? (Why do you speak so loud?)
Porquê confundir isto tudo? (Why mixing up all this?)
In European Portuguese we write (por quê) "porquê" all together; in Brazilian Portuguese the same interrogative adverb is written separately.
This is a short and brief explanation of their meaning. I hope you can understand it now!
See you,
sflor