Atomic Radii
Examines the size of an atom, including covalent, metallic, and van der Waals radii, and their trends across periods and down groups.
What is Atomic Radii?
A measure of the size of an atom, often defined as half the distance between the nuclei of two identical atoms bonded together.
Key points
- Define and differentiate between covalent, metallic, and van der Waals radii.
- Explain the factors affecting atomic size.
- Predict the trend of atomic radii across a period and down a group.
- Analyze exceptions to the general trends in atomic radii.
Common exam trap
Confusing the trends in atomic radii with ionization enthalpy or electronegativity.
Definitions
- Term
Atomic Radius
- Meaning
A measure of the size of an atom, often defined as half the distance between the nuclei of two identical atoms bonded together.
- Term
Covalent Radius
- Meaning
Half the distance between the nuclei of two identical atoms joined by a single covalent bond.
- Term
Metallic Radius
- Meaning
Half the distance between the nuclei of two adjacent metal atoms in a solid metallic crystal.
- Term
Van der Waals Radius
- Meaning
Half the distance between the nuclei of two adjacent, non-bonded atoms in a solid, representing the closest approach of two atoms not chemically bonded.
- Term
Effective Nuclear Charge (Zeff)
- Meaning
The net positive charge experienced by an electron in a multi-electron atom, considering the shielding effect of inner electrons.
Learning objectives
Define and differentiate between covalent, metallic, and van der Waals radii.
Explain the factors affecting atomic size.
Predict the trend of atomic radii across a period and down a group.
Analyze exceptions to the general trends in atomic radii.
Prerequisites
Atomic Structure (protons, neutrons, electrons, electron shells)
Periodic Table trends (groups and periods)
Effective Nuclear Charge and Shielding Effect
Types of Chemical Bonds (covalent, metallic)
Common mistakes
Confusing the trends in atomic radii with ionization enthalpy or electronegativity.
Not considering the different types of radii (covalent, metallic, van der Waals) when comparing elements.
Overlooking exceptions to the general trends, especially in transition elements or due to electron-electron repulsion.
Keywords
Atomic Radius
Covalent Radius
Metallic Radius
Van der Waals Radius
Periodic Trends
Effective Nuclear Charge
Shielding Effect
Atomic Size
Practice preview
What is the correct order of atomic radii for the following elements: Li, Be, B, C?…
easy
Which of the following statements is INCORRECT regarding atomic radii?…
medium
Which element among the following has the largest atomic radius?…
easy