Yes, you are eligible to give the exam. 

For addmission in B.arch, the candidate should have 50% marks in each Physics , chemistry and mathematics and 50% in total in the class 12th examination. 

Jee mains being an exam conducted in very large scale. So it has some eligibility criteria. In which its given that you must have aggregate of 50% in pcm. So if your physics chemistry and maths marks aggregate is above 50% then you are   elligible for jee mains paper 2. All the best for your jee mains.