Which of the following species has the greatest
number of electrons?
1. cl1−
2. co4+
3. fe2+
4. v
5. sc2−

Option (3) is the correct answer.

Explanation:

When there is a negative charge on an atom then we add the charge with the number of electrons. Whereas when there is a positive charge on an atom then we subtract the charge from the number of electrons.

Atomic number of chlorine is 17. So, number of electrons present in is 17 + 1 = 18 electrons.

Atomic number of cobalt is 27. So, number of electrons present in is 27 - 4 = 23 electrons.

Atomic number of iron is 26. So, number of electrons present in is 26 - 2 = 24 electrons.

Atomic number of vanadium is 23. So, number of electrons present in V is 23 electrons.

Atomic number of scandium is 21. So, number of electrons present in is 21 + 2 = 23 electrons.

Thus, we can conclude that out of the given species, has the greatest  number of electrons.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.