F.Y.B.Sc. Chem-I Unit 2.2 Quiz

Questions and Answers

What is the covalent radius of chlorine?

7.2 x 10—2 nm

9.9 x 10—2 nm (correct)

19.8 x 10—2 nm

14.9 x 10—2 nm

Which statement is true regarding covalent radii?

Covalent radii are larger than van der Waals radii.

Covalent radii are determined by measuring ionic bond lengths.

Covalent radii cannot be used to calculate bond lengths.

The bond length of non-polar heteronuclear diatomic molecules is the sum of their covalent radii. (correct)

What is the significance of van der Waals radii?

They help determine ionic bond lengths directly.

They are significantly smaller than covalent radii.

They determine the exact position of bonded atoms.

They account for electron cloud repulsions in non-bonded atoms. (correct)

How does the formation of cations affect atomic radius?

Cations have a greater nuclear charge than the extranuclear charge. Signup and view all the answers

What happens to the atomic radius of anions when electrons are added?

Anions expand in size compared to their respective atoms. Signup and view all the answers

How can ionic radii be determined?

By measuring the lengths of ionic bond lengths in ionic compounds. Signup and view all the answers

Which is true regarding the relationship between covalent and van der Waals radii?

Covalent radii are smaller than van der Waals radii due to orbital overlap. Signup and view all the answers

What is the bond length between two chlorine atoms?

19.8 x 10—2 nm Signup and view all the answers

What is the definition of atomic radius?

The distance from the nucleus to the outermost electron in the highest energy level. Signup and view all the answers

How does atomic size generally trend across a period in the periodic table?

It decreases as nuclear attraction on the outermost electrons increases. Signup and view all the answers

Which statement correctly describes the effect of ionic size on basicity?

Smaller cations are less basic in nature. Signup and view all the answers

What is the relationship between ionic size and hydration?

Smaller ions undergo hydration to a greater extent. Signup and view all the answers

What impacts the complexing power of ions?

Smaller ions have greater complexing power. Signup and view all the answers

Which factor affects the extent of ionicity in a covalent bond?

The sizes of the cation and anion. Signup and view all the answers

Which of the following statements about cation size is correct?

Cations are always smaller than the neutral atom from which they are formed. Signup and view all the answers

What is the effect of packing of ions in a crystal lattice?

It determines the ion's ability to conduct electricity. Signup and view all the answers

What does the atomic radius represent in an atom or ion?

The distance between the nucleus and the electron in its highest energy level Signup and view all the answers

How does the surrounding environment affect the size of an atom?

It changes the electron probability distribution around the nucleus. Signup and view all the answers

How is the covalent radius defined?

Half of the covalent bond length when two atoms are bonded Signup and view all the answers

What is a challenge in measuring the absolute size of an atom or ion?

Electrons do not have a fixed position. Signup and view all the answers

Which of the following is NOT a characteristic of van der Waals radii?

They account for the electronegativity of atoms. Signup and view all the answers

How is the ionic radius typically determined?

Using internuclear distances in ionic compounds Signup and view all the answers

What might influence the covalent radius during measurement?

Overlap of outermost orbitals of the atoms Signup and view all the answers

Which of the following statements about atomic radii is true?

Atomic radii vary according to the surrounding atomic environment. Signup and view all the answers

Study Notes

Covalent Radii

Chlorine's covalent radius is calculated at 9.9 x 10–2 nm; this is derived from the bond length between two chlorine atoms, which is 19.8 x 10–2 nm.
In non-polar heteronuclear diatomic molecules, the bond length approximates the sum of the covalent radii of the atoms involved.
For example, the C-F bond length measures 14.9 x 10–2 nm, with a covalent radius of carbon at 7.7 x 10–2 nm, leading to fluorine's atomic radius being 7.2 x 10–2 nm.

Van der Waals Radii

Van der Waals radii represent the shortest distance between atoms not chemically bound, where only van der Waals forces are present.
These radii are generally larger than covalent radii due to the lack of orbital overlap when atoms are not bonded.

Ionic Radii

Ionic radii are determined by measuring ionic bond lengths in ionic compounds.
Cations (positively charged ions) are smaller than their parent atoms due to loss of electrons, leading to a stronger nuclear charge. Example: Sodium (Na) has a radius of 15.4 x 10–2 nm, while Na+ is 9.7 x 10–2 nm.
Anions (negatively charged ions) are larger than their parent atoms because they gain electrons, resulting in a reduced effective nuclear charge.

Slater's Rules

Slater’s rules provide a method to calculate the effective nuclear charge (Z*) experienced by an electron.
For a Cu atom, with Z = 29, the calculated Z* felt by a 4s electron is 3.70 using the proper substitution based on electron configuration.

Atomic Radii

Atomic radius reflects the size of an atom, defined as the distance from the nucleus to the electron in its highest energy level.
Absolute sizes of atoms cannot be precisely defined due to uncertainty in electron positions and surrounding influence, prompting the use of internuclear distances for measurements.

Effects of Atomic and Ionic Radii

Physical characteristics like atomic and ionic radii influence chemical behavior.
Smaller cations exhibit lower basicity; e.g., lithium oxides are less basic than those of other alkali metals.
Smaller ions experience greater hydration, with Li+ showing the maximum hydration among alkali metals.
Small ions are more effective in complexing, leading to more stable complexes.
Chemical reactivity is influenced by atomic sizes, affecting the ability to gain, share, or lose electrons.

Trends in Atomic Size Across a Period

Moving across a period in the periodic table, the atomic number increases, resulting in greater nuclear charge while the number of electron shells remains constant.
This increase in nuclear attraction leads to a decrease in atomic size due to enhanced attraction between the nucleus and the outermost electrons.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your understanding of covalent radii and bond lengths in chemistry, focusing on the periodic table and periodicity of properties. This quiz will cover concepts related to chlorine's covalent radius and diatomic molecules. Perfect for F.Y.B.Sc. students in their Chemistry I course.