Question

Which of the following are correct here? (1) E.N \(\rightarrow \mathrm{F}>\mathrm{O}>\mathrm{N}>\mathrm{P}\) (2) I.E \(\rightarrow \mathrm{F}>\mathrm{N}>\mathrm{O}>\mathrm{P}\) (3) E.A \(\rightarrow F>O>P>N\) (4) Size \(\rightarrow \mathrm{F}>\mathrm{P}>\mathrm{N}>\mathrm{O}\) (a) 1,2 (b) \(1,2,3\) (c) \(1,2,4\) (d) \(1,2,3,4\)

Short answer

Answer: (a) 1,2

Step-by-step solution

Evaluate Electronegativity (E.N)

Electronegativity increases across a period from left to right. Therefore, it typically follows the order: Fluorine (F) > Oxygen (O) > Nitrogen (N) > Phosphorus (P). Thus, statement (1) is correct.

Evaluate Ionization Energy (I.E)

Ionization Energy generally increases across a period from left to right. However, there are exceptions like between O and N, where oxygen has slightly lower ionization energy due to electron pairing in its p orbitals. Thus, the order is: F > N > O > P, making statement (2) correct.

Evaluate Electron Affinity (E.A)

Electron affinity also increases across a period since atoms are more eager to complete their valence shell; hence, F has a high E.A. However, O has higher electron affinity than N and typically higher than P. The order provided is incorrect (F > O > N > P is the correct order), making statement (3) incorrect.

Evaluate Atomic Size

Atomic size decreases across a period from left to right. Therefore, the correct order should be: P > N > O > F. The given order (F > P > N > O) is incorrect, making statement (4) incorrect.

Conclusion: Determine Correct Statements

Statements (1) and (2) are correct after evaluation, while statements (3) and (4) are incorrect.

Key concepts

Electronegativity

Electronegativity refers to the ability of an atom to attract electrons towards itself when it forms a chemical bond. As you move across a period from left to right on the periodic table, electronegativity increases. This is because the atomic nuclei become more positively charged, improving their ability to attract electrons.
Among the elements given — fluorine (F), oxygen (O), nitrogen (N), and phosphorus (P) — fluorine is the most electronegative. This trend can be observed clearly in the order: F > O > N > P. This makes fluorine extremely effective at gaining electrons from other atoms, leading to strong bonds. It's this property that makes statement (1) in the exercise correct.

Ionization Energy

Ionization energy is the energy required to remove an electron from an atom. It generally increases as you move across a period because the electrons are held more tightly by the increasing positive charge of the nucleus. However, there are exceptions to this pattern due to the electronic configuration of the atoms.
For instance, while you might expect oxygen to have higher ionization energy than nitrogen, nitrogen actually has a slightly higher ionization energy because it has half-filled p orbitals, which are more stable. Hence, with the elements fluorine (F), nitrogen (N), oxygen (O), and phosphorus (P), the correct order is F > N > O > P. Statement (2) in the exercise correctly accounts for this anomaly.

Electron Affinity

Electron affinity is the amount of energy released when an atom in the gaseous state gains an electron. Generally, electron affinity increases across a period due to an increase in nuclear charge. However, specific exceptions can be found due to the electron configurations of different elements.
In the case of the elements fluorine (F), oxygen (O), nitrogen (N), and phosphorus (P), while you can typically expect oxygen to have a higher electron affinity than nitrogen, phosphorus may still have a lower electron affinity than nitrogen due to its place in the periodic table. The exercise provided an incorrect order (F > O > P > N), since a more accurate pattern is F > O > N > P, making statement (3) incorrect.

Atomic Size

Atomic size, or atomic radius, refers to the distance from the nucleus to the outermost shell of an electron. As you traverse a period from left to right, atomic size decreases. This happens because the greater nuclear charge pulls the electron cloud closer to the nucleus, reducing the size of the atom.
The given order for atomic size in the exercise was F > P > N > O, which is incorrect. In reality, phosphorus, a larger atom, should come first, followed by nitrogen, then oxygen, and finally, the smallest, fluorine, making the correct order: P > N > O > F. This discrepancy highlights why statement (4) is incorrect in the context of this exercise.