AP EAMCET · Chemistry · Classification of Elements and Periodicity in Properties

In second period of the long form of the periodic table, an element $X$ has second lowest first ionization enthalpy and element $Y$ has second highest first ionization enthalpy values. What are $X$ and $Y$ ?

A $B, F$
B $Be, Ne$
C $Be, O$
D $C, O$

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Answer & Solution

Correct Answer

(A) $B, F$

Step-by-step Solution

Detailed explanation

The order of ionization enthalpy of elements of 2nd period in long form of periodic table is Li<B<Be<C<O<N<F<Ne. Generally, on going left to right in a period, ionization energy increases, but there are some exceptions to this. For example, Be has…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match the following.

List - $I$ Reaction		List - $II$ Catalyst
$(A)$	$N_{2} (g) + 3 H_{2} (g) ⟶ 2 {NH}_{3} (g)$	$(I)$	$Ni$
$(B)$	$2 H_{2} (g) + O_{2} (g) ⟶ 2 H_{2} O (l)$	$(II)$	$Pt$
$(C)$	$CO (g) + 3 H_{2} (g) ⟶ {CH}_{4} (g) + H_{2} O (g)$	$(III)$	$ZnO - {Cr}_{2} O_{3}$
$(D)$	$CO (g) + 2 H_{2} (g) ⟶ {CH}_{3} OH (g)$	$(IV)$	$Fe$

The correct answer is:

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In second period of the long form of the periodic table, an element X has second lowest first ionization enthalpy and element Y has second highest first ionization enthalpy values. What are X and Y ?

Step-by-step Solution

In second period of the long form of the periodic table, an element $X$ has second lowest first ionization enthalpy and element $Y$ has second highest first ionization enthalpy values. What are $X$ and $Y$ ?