Which of the following statements is/are correct? i. Principal energy levels are identified by the letters s, p, d, and f. ii. Principal energy levels appear in both the quantum mechanical model of the atom and the Bohr model of the atom. iii. In general, n = 1 is at lower energy than n = 2, and n = 2 is lower than n = 3, and so on. iv. The principal energy level is related to electron spin. a. i only b. iv only c. i and ii d. ii and iii e. iii and iv

d. ii and iii

Explanation:

Both the Bohr model and the wave (quantum) mechanical  models of the atom recognize the principal quantum number n. The principal quantum number shows the shell or energy level where an electron may be found.

The energy levels are arranged in increasing order of magnitude. That is n=1 >n=2=n=3 etc

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.