The F- And D- Block Elements - Variation Of Atomic Size

The f- and d-block elements - Variation of Atomic size

The size of atoms in the f-block and d-block elements varies across periods and down groups.
In the d-block elements, atomic size decreases across a period due to increased effective nuclear charge.
In the f-block elements, atomic size experiences a variation known as the lanthanide contraction and actinide contraction.

Variation of Atomic Size - Periodic Trend

Atomic size decreases across a period in the d-block elements.
This is due to the increase in effective nuclear charge, pulling the electrons closer to the nucleus.
As atomic number increases, the number of protons also increases, intensifying the attractive force and decreases the size.

Variation of Atomic Size in the d-Block Elements

Transition metals have multiple oxidation states.
The effective nuclear charge increases due to the addition of electrons to the same energy level.
The attraction between the nucleus and electrons intensifies, resulting in a decrease in atomic size.

Variation of Atomic Size - Group Trend

Atomic size generally increases as you move down a group in the d-block elements.
This is because the number of energy levels increases, leading to larger atomic size.
Each period represents the filling of a new shell.

Variation of Atomic Size in the f-Block Elements: Lanthanide Contraction

The f-block elements, also known as the lanthanides and actinides, exhibit a unique variation in atomic size.
Lanthanide contraction is the decrease in atomic size from lanthanum (La) to lutetium (Lu).
This contraction occurs due to poor shielding of the 4f electrons resulting in a stronger nuclear attraction.

Variation of Atomic Size in the f-Block Elements: Actinide Contraction

Similar to the lanthanides, the actinides also show a contraction in atomic size.
Actinide contraction occurs from actinium (Ac) to lawrencium (Lr).
It is caused by poor shielding of the 5f electrons, leading to a stronger attraction between the nucleus and outer electrons.

Examples of Atomic Size Variation

Example 1: In period 4, titanium (Ti) has a smaller atomic size than scandium (Sc) due to increased effective nuclear charge.
Example 2: In the d-block, copper (Cu) has a smaller atomic size than nickel (Ni) due to the presence of additional 3d electrons.

Equations Relevant to Atomic Size Variation

Equation 1: Effective Nuclear Charge (Zeff) = Atomic Number (Z) - Shielding Effect (S)
Equation 2: Atomic Size (r) = Distance between the nucleus and the outermost electron
Equation 3: Atomic size increases as the number of energy levels (n) increases (r ∝ n)

Summary

Atomic size decreases across a period in the d-block elements due to increased effective nuclear charge.
Atomic size generally increases down a group in the d-block elements.
In the f-block elements, both lanthanide contraction and actinide contraction lead to a decrease in atomic size.

Key Takeaways

The size of atoms in the f-block and d-block elements varies across periods and down groups.
Lanthanide contraction and actinide contraction result in a decrease in atomic size.
Effective nuclear charge, shielding effect, and the number of energy levels play crucial roles in the variation of atomic size.

The Effect of Electron Configuration on Atomic Size

The electron configuration of an atom affects its size.
The more electrons in the outermost energy level, the larger the atom.
Example: Potassium (K) has a larger atomic size than chlorine (Cl) due to the additional electron in the 4s orbital.

Variation of Atomic Size in the s-Block Elements

Atomic size increases down a group in the s-block elements.
This is due to the addition of new energy levels as we move down the periodic table.
Example: Atomic size of lithium (Li) is larger than sodium (Na) due to the presence of an additional energy level in sodium.

Variation of Atomic Size in the p-Block Elements

Atomic size generally decreases across a period in the p-block elements.
This is due to the increase in effective nuclear charge.
Example: Oxygen (O) has a smaller atomic size than nitrogen (N) due to the increased number of protons in the nucleus.

Variation of Atomic Size in the Noble Gases

Noble gases have the largest atomic sizes within their respective periods.
This is because they have completely filled electron shells and exhibit excellent shielding.
Example: Helium (He) has a smaller atomic size than neon (Ne) due to the addition of an energy level in neon.

Ionization Energy and Atomic Size

Ionization energy is the energy required to remove an electron from an atom.
Atomic size affects ionization energy: larger atoms have lower ionization energies.
Example: The ionization energy of lithium (Li) is lower than that of beryllium (Be) due to the larger atomic size of lithium.

Electronegativity and Atomic Size

Electronegativity is the tendency of an atom to attract electrons towards itself.
Atomic size affects electronegativity: larger atoms have lower electronegativities.
Example: Chlorine (Cl) has a higher electronegativity than iodine (I) due to the smaller atomic size of chlorine.

Relationship between Atomic Size and Metallic Character

Atomic size is inversely proportional to metallic character.
Larger atoms have more loosely held valence electrons, allowing for better conductivity.
Example: Sodium (Na) exhibits higher metallic character than magnesium (Mg) due to its larger atomic size.

Quantum Numbers and Atomic Size

Atomic size can be explained using quantum numbers.
The principal quantum number (n) determines the energy level and consequently, the atomic size.
Example: An atom with n=3 has a larger atomic size than an atom with n=2.

Factors Affecting Atomic Size

Effective nuclear charge, shielding, and the number of energy levels are the main factors affecting atomic size.
Effective nuclear charge increases across a period, decreasing atomic size.
Example: The atomic size of carbon (C) is smaller than nitrogen (N) due to the increased effective nuclear charge.

Summary

Atomic size is influenced by electron configuration, effective nuclear charge, shielding effect, and the number of energy levels.
Atomic size generally increases down a group and decreases across a period.
Understanding the variation of atomic size helps explain trends in ionization energy, electronegativity, metallic character, and other chemical properties.

Summary of Atomic Size Variation

Atomic size decreases across a period in the d-block elements due to increased effective nuclear charge (Zeff).
Atomic size generally increases down a group in the d-block elements due to the addition of energy levels (n).
Lanthanide contraction and actinide contraction lead to a decrease in atomic size in the f-block elements.
The electron configuration, shielding effect, and number of energy levels play crucial roles in determining atomic size.

Example: Atomic Size Comparison

Compare the atomic sizes of elements calcium (Ca) and barium (Ba).
Ca (atomic number 20) has a smaller atomic size than Ba (atomic number 56).
This can be attributed to the increased effective nuclear charge in Ba, resulting in a stronger attraction between the nucleus and electrons.

Equations: Effective Nuclear Charge (Zeff)

Equation: Effective Nuclear Charge (Zeff) = Atomic Number (Z) - Shielding Effect (S).
Higher Zeff leads to a stronger attraction between the nucleus and electrons, resulting in a smaller atomic size.
Example: As the atomic number increases from 3 to 7, the effective nuclear charge increases, causing a decrease in atomic size in boron (B) to nitrogen (N).

Equations: Atomic Size (r)

Equation: Atomic size (r) = Distance between the nucleus and the outermost electron.
Atomic size increases as the number of energy levels (n) increases.
Example: The atomic size of sodium (Na) is larger than lithium (Li) due to the additional energy level in sodium.

Example: Lanthanide Contraction

Lanthanide contraction refers to the decrease in atomic size from lanthanum (La) to lutetium (Lu).
It occurs due to poor shielding of the 4f electrons, leading to a stronger nuclear attraction.
The smaller atomic size of Lu compared to La is an example of lanthanide contraction.

Example: Actinide Contraction

Actinide contraction occurs from actinium (Ac) to lawrencium (Lr) in the actinide series.
It is caused by poor shielding of the 5f electrons, resulting in a stronger attraction between the nucleus and outer electrons.
The decrease in atomic size from Ac to Lr demonstrates actinide contraction.

Example: Variation of Atomic Size in the d-Block Elements

Atomic size decreases across a period in the d-block elements.
For example, the atomic size of iron (Fe) is smaller than manganese (Mn) due to the increased effective nuclear charge and stronger attraction between the nucleus and electrons.

Example: Variation of Atomic Size in the f-Block Elements

Atomic size variation in the f-block elements is observed due to lanthanide and actinide contractions.
For example, the atomic size of gadolinium (Gd) is smaller than that of yttrium (Y) due to the lanthanide contraction.

Relationship between Atomic Size and Ionization Energy

Atomic size and ionization energy are inversely proportional.
Larger atoms have more loosely held valence electrons, resulting in lower ionization energies.
For example, the ionization energy of cesium (Cs) is lower than fluorine (F) due to the larger atomic size of cesium.

Relationship between Atomic Size and Electronegativity

Atomic size and electronegativity are inversely proportional.
Larger atoms have lower electronegativities as they have less ability to attract electrons.
For example, the electronegativity of rubidium (Rb) is lower than oxygen (O) due to the larger atomic size of rubidium.