Energy of an electron in the ground state of the hydrogen atom is - 2 .18 × 10 - 18 J . Calculate the ionization enthalpy of atomic hydrogen in terms of J mol ‐ 1 .

The energy of an electron in the ground state of the hydrogen atom is - 2 .18 x 10 - 18 J . Therefore, the energy required to remove that electron from the ground state of the hydrogen atom (Ionization enthalpy) = 2 .18 × 10 - 18 J . Hence, ionization enthalpy of atomic hydrogen in terms of J mol - 1 = 2 .18 × 10 - 18 × N A J mol - 1 = 2 .18 × 10 - 18 × 6 .022 × 10 23 J mol - 1 = 1 .31 × 10 6 Jmol - 1 .

The first ionization enthalpy values ( in KJ mol - 1 ) of group 13 elements are: B Al Ga In Tl 801 577 579 558 589 How would you explain this deviation from the general trend?

Generally, on moving down the group, ionization enthalpy generally decreases due to an increase in the atomic size and shielding. Ionization energy ∝ 1 atomic size Ionization energy ∝ 1 shielding effect Thus, on moving down the group, ionization enthalpy decreases from B to Al . But, Ge has higher ionization enthalpy than Al . Al follows immediately after s ‐ block elements, whereas, Ga follows after d ‐ block elements. The shielding provided by d ‐electrons is not very effective. These electrons do not shield the valence electrons very effectively. As a result, the valence electrons of Ga experience a greater effective nuclear charge than those of Al . Further, moving from Ga to In , the ionization enthalpy decreases due to an increase in the atomic size and shielding. But, on moving from In to Tl , the ionization enthalpy again increases. In the periodic table, Tl follows after 4 f and 5 d electrons, The shielding provided by the electrons in both these orbitals is not very effective. Therefore, the valence electron is held quite strongly by the nucleus. Hence, the ionization energy of Tl is on the higher side.

MEDIUM

11th CBSE

IMPORTANT

Earn 100

What is the significance of the terms — ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy?

Hint: Requirements for comparison purposes.

Important Questions on Classification of Elements and Periodicity in Properties

MEDIUM

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.15

Energy of an electron in the ground state of the hydrogen atom is

- 2 .18 \times 10^{- 18} J .

Calculate the ionization enthalpy of atomic hydrogen in terms of

J {mol}^{‐ 1} .

MEDIUM

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.16

Among the second period elements the actual ionization enthalpies are in the order

Li < B < Be < C < O < N < F < Ne .

Explain why

Be

has higher

∆_{i} H

than

B

HARD

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.16

Among the second period elements the actual ionization enthalpies are in the order

Li < B < Be < C < O < N < F < Ne .

Explain why

O

has lower

∆_{i} H

than

N and F

MEDIUM

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.17

How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?

MEDIUM

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.18

What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?

HARD

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.19

The first ionization enthalpy values

(in KJ {mol}^{- 1})

of group

13

elements are:

$B$	$Al$	$Ga$	$In$	$Tl$
801	577	579	558	589

How would you explain this deviation from the general trend?

MEDIUM

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.2

Which of the following pair of elements would have a more negative electron gain enthalpy?

$O or F$

HARD

11th CBSE

IMPORTANT

Textbook for Class XI Chemistry Part I>Chapter 3 - Classification of Elements and Periodicity in Properties>EXERCISES>Q 3.2

Which of the following pair of elements would have a more negative electron gain enthalpy?

$F$ or $Cl$

What is the significance of the terms — ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy? Hint: Requirements for comparison purposes.

Important Questions on Classification of Elements and Periodicity in Properties

Learn and Prepare for any exam you want !

What is the significance of the terms — ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy?

Hint: Requirements for comparison purposes.