10 Questions
What is the definition of atomic radius?
The distance between the centre of the nucleus to the point where the electron density is effectively zero.
Explain how atomic size changes across a period.
Atomic size decreases across a period due to increased nuclear charge while the number of core electrons remains the same, leading to an increase in effective nuclear charge.
How does atomic size change down a group?
Atomic size increases down a group as more distant electron shells are occupied while the effective nuclear charge remains the same.
Define covalent radius.
Covalent radius is half the distance between the nuclei of two covalently bonded atoms of the same element in a molecule.
What is the formula for calculating the bond length rA-B in homonuclear diatomic molecules?
The bond length rA-B is given by rA-B = rA + rA, or rA-B = 2 * rA, where rA is the covalent radius.
Explain the trend of atomic size across a period and down a group in the periodic table.
Across a period, atomic size decreases due to increased nuclear charge and the same number of core electrons, leading to a higher effective nuclear charge pulling the outer electrons closer to the nucleus. Down a group, atomic size increases due to the occupation of more distant electron shells while the effective nuclear charge remains the same.
What is the definition of covalent radius and how is it related to covalently bonded atoms?
Covalent radius is half the distance between the nuclei of two covalently bonded atoms of the same element in a molecule. In the case of homonuclear diatomic molecules, the bond length rA-B is given by rA-B = rA + rA, so rA = rA-B/2.
Define atomic and ionic radius. How do they change across a period and down a group?
Atomic radius is the distance between the center of the nucleus to the point where the electron density is effectively zero. Ionic radius is the distance between the nucleus and the outermost electron in an ion. Across a period, atomic and ionic sizes decrease due to increased nuclear charge and closer outer electrons. Down a group, atomic and ionic sizes increase due to the occupation of more distant electron shells.
Compare the atomic sizes of Na and Mg based on their electron configurations.
Na has an atomic size of 1.91 Å with the electron configuration 1s22s22p63s1, while Mg has an atomic size of 1.60 Å with the electron configuration 1s22s22p63s2. Therefore, Na has a larger atomic size than Mg.
Explain the relationship between the number of core electrons, effective nuclear charge, and atomic size.
As the number of core electrons remains the same, an increase in nuclear charge leads to a higher effective nuclear charge, pulling the outer electrons closer to the nucleus and resulting in a decrease in atomic size.
Test your knowledge of atomic and ionic radius in this quiz about the periodicity of elements. Explore the trends in size across the periodic table and understand how atomic size changes within groups and periods.
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