Atomic and Ionic Sizes
Analysis of trends in atomic and ionic radii across periods and down groups, including the effect of lanthanoid contraction.
What is Atomic and Ionic Sizes?
Half the distance between the nuclei of two identical atoms bonded together.
Key points
- Explain the trend of atomic and ionic radii across a period for transition elements.
- Analyze the reasons behind the less pronounced decrease in radii.
- Describe the impact of lanthanoid contraction on the sizes of subsequent elements.
- Compare the atomic and ionic radii of different transition elements.
Common exam trap
Assuming a uniform decrease in radii across the entire period.
Definitions
- Term
Atomic Radius
- Meaning
Half the distance between the nuclei of two identical atoms bonded together.
- Term
Ionic Radius
- Meaning
Half the distance between the nuclei of two ions in an ionic compound.
- Term
Shielding Effect
- Meaning
The reduction of the effective nuclear charge experienced by an electron due to the presence of other electrons between it and the nucleus.
- Term
Lanthanoid Contraction
- Meaning
The gradual decrease in the atomic and ionic radii of the lanthanoid elements across the series, leading to similar sizes in the subsequent 4d and 5d transition series.
Learning objectives
Explain the trend of atomic and ionic radii across a period for transition elements.
Analyze the reasons behind the less pronounced decrease in radii.
Describe the impact of lanthanoid contraction on the sizes of subsequent elements.
Compare the atomic and ionic radii of different transition elements.
Prerequisites
Understanding of atomic structure and electronic configuration.
Knowledge of periodic trends in atomic radii.
Concept of nuclear charge and shielding effect.
Understanding of ionization energy.
Common mistakes
Assuming a uniform decrease in radii across the entire period.
Overlooking the effect of lanthanoid contraction on 4d and 5d series.
Confusing atomic and ionic radii trends.
Underestimating the shielding effect of d-electrons.
Keywords
Transition elements
Atomic radius
Ionic radius
Periodic trends
Shielding effect
Lanthanoid contraction
Nuclear charge
Electronic configuration
Practice preview
Which of the following ions has the largest ionic radius?…
easy
The lanthanoid contraction is responsible for the fact that:…
medium
Which of the following has the smallest ionic radius?…
medium