18 Questions
What method can be used to measure the interatomic distance between two different ions accurately?
X-ray crystallography
How do common cations generally compare in size to common anions?
Smaller
What contributes to the increase in size of an atom during anion formation?
Addition of an electron causing increased inter-electronic repulsion
In the series of isoelectronic species N3-, O2-, Ne, Na+, Mg2+, and Al3+, what trend is observed regarding their radii?
Decrease in size from anions to cations
How does the effective nuclear charge affect the radius of a species?
Greater effective nuclear charge leads to smaller radius
Why is knowledge of atomic radii considered essential?
To accurately predict atom behavior
What does the radius of an atom represent?
Distance from nucleus to where electron density is virtually zero
Why is it important to measure atomic radii?
To study the relationship between atomic properties like ionization energy and electron affinity
In what way is the wave mechanical picture of an atom different from a ball?
An atom's electron cloud has no definite boundary surface
How does the size of an atom change when it is present as a cation or anion?
Varies based on the type of cation or anion
How is the measurement of atomic radii affected by the state of an atom (gas vs. lattice site)?
The measurement is larger in gas state compared to a lattice site
Why do we need to define and accurately measure atomic radii under different conditions?
Because atomic radii vary based on different atomic states
Which of the following statements about atomic radii is correct?
Atomic radii generally increase going down a group in the periodic table.
Which type of radius is measured between the centers of two adjacent atoms in a solid?
Metallic radius
If an atom loses an electron, its resulting ionic radius will be:
Smaller than its atomic radius
Which of the following is the correct order of increasing radii for the fluorine atom?
Ionic radius < Covalent radius < Van der Waals radius
Which of the following elements has the largest atomic radius among the elements in the third period?
Argon (Ar)
Which of the following statements about covalent radii is correct?
Covalent radii are measured from the center of one atom to the center of another in a covalent bond.
Study Notes
Atomic Radii
- Atomic radii are the measure of the size of an atom, which is essential for predicting the action of an atom.
- Atomic radii are related to other atomic properties like ionization energy, electron affinity, and electronegativity.
Measurement of Atomic Radii
- Atomic radii are defined as the distance from the center of the nucleus to the point where the electron density is virtually zero.
- The size of an atom can be defined, but measuring it is a problem due to the varying conditions under which an atom exists (e.g., in a lattice site of a crystal or in a gaseous state).
Types of Atomic Radii
- There are different types of atomic radii, including:
- Covalent radius
- Vander Waal's radius
- Metallic radius
- Ionic radius (cation and anion radii)
Ionic Radii
- Ionic radii are estimated and not measured absolutely, so they are not completely accurate or reliable.
- Cation radii are smaller than anion radii, except for rubidium and caesium cations, which are the largest single atom cations.
- The size of anions increases due to an increase in inter-electronic repulsion in the valence shell and a decrease in effective nuclear charge.
- The greater the effective nuclear charge, the smaller the radius of the species.
Test your knowledge on rules governing the filling of electrons in orbitals, electronic configuration of ions, and the division of elements into blocks. This quiz also covers atomic radii, covalent radius, Vander Waal's radius, metallic radius, and ionic radius.
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