If you look at the periodic table of elements, you can see that atomic number for phosphorus is 15. It means that it has 15 electrons and 15 protons total. Now you can write configuration for P which is: 1s22s22p63s23p3. or [Ne] 3s2<span> 3p</span><span>3 </span><span>
From here, you can see that it has 5 valence electrons (s2+p3).
In the periodic table of elements the number of protons+ number of neutrons is determined as atomic mass. Atomic mass of the P is 30.
number of neutrons = atomic mass-atomic number
number of neutrons = 30-15
number of neutrons= 15 </span>
Im not 100% sure, but I think the answer is C. If not, Im sorry for bothering you.
(2) 2 - 7 - 18 - 7 does, because the electron from the L shell jumped to the N shell, which requires energy.
The rest of them are either different types of atoms (different elements) or are not the excited state (ground state)
Answer : The correct option is, (C) 6
Explanation :
Oxidation-reduction reaction : It is a reaction in which oxidation and reduction reaction occur simultaneously.
Oxidation reaction : It is the reaction in which a substance looses its electrons. In this oxidation state increases.
Reduction reaction : It is the reaction in which a substance gains electrons. In this oxidation state decreases.
The given unbalanced chemical reaction is,

Half reactions of oxidation and reduction are :
Oxidation :
......(1)
Reduction :
.......(2)
In order to balance the electrons, we multiply equation 1 by 2 and equation 2 by 3, we get:
Oxidation :
......(1)
Reduction :
.......(2)
The overall balanced chemical reaction will be:

From this reaction we conclude that the electrons are getting transferred from iron to iodine and the number of electrons transferred are 6 electrons.
Hence, the correct option is, (C) 6
The balanced equation is 2HgO --> 2Hg + O2