An element X contains 35 electrons, 45 neutrons
i. The number of protons must be equal to the number of electrons. So the number of protons = 35.
ii. Number of electrons = 35. So the electronic configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 .
iii. The last electron i.e. 5th electron in 4p orbital has the following quantum numbers. n = 4, l = 1, m = +1, s = +1/2