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Questions and Answers
Which of the following statements about electron affinity is true?
Which of the following elements has the largest ionic radius?
What is the correct order of increasing ionic radii?
What is the electron affinity of an element that requires energy to accept an electron?
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Which of the following elements has a high electronegativity?
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What is the trend of electron affinity across a period?
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Which of the following elements has ns2-np5 electron configuration?
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Which of the following statements about electronegativity is true?
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Which of the following elements has a low electron affinity?
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What is the correct order of electronegativity of the following elements?
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Study Notes
Electron-Deficient Molecules
- Contain either Be or B as the central atom
- Have fewer than 8 electrons around the central atom (4 e- around Be and 6 e- around B)
- Examples: BF3
Odd-Electron Molecules
- Have an odd number of valence electrons
- Examples: free radicals, NO2, CH3, OH, H, etc.
- Contain a lone (unpaired) electron and are paramagnetic
Expanded Valence Shells
- Occur when a central atom has more than 8 electrons around it
- Use empty outer d orbitals
- Occurs only with central atoms from Period 3 or higher
- Examples: SF6, PCl5, H2SO4, H3PO4
VSEPR Theory
- Enables prediction of molecular structure and approximate bond angles
- Assumes electron pairs in the valence shell of a central atom will adopt an arrangement that minimizes repulsions
- Electrons form either bonding pairs or lone pairs
- Electron pairs arrange to maximize distance between them
Octet Rule
- States that atoms tend to gain, lose, or share electrons to attain the electronic configuration of the nearest noble gas
- Applies to all types of bonding
- Atoms tend to achieve an octet (8) electrons in their highest occupied energy level
Bonding
- The joining of at least two atoms to form a molecule or compound
- Involves the valence shell electrons
- A chemical bond is a mutual electrical attraction between nuclei and valence electrons
Ionic Radii
- Increase down a group in the periodic table
- Decrease across a period in the periodic table
- Example: Al3+ < Ca2+
Electron Affinity (EA)
- Defined as the energy released when an electron is added to an isolated gaseous atom
- Can be either endothermic or exothermic
- Negative values indicate energy is released, while positive values indicate energy is required
Electro-negativity (EN)
- Measures the relative tendency of an atom to attract electrons
- Elements with high electro-negativities (nonmetals) often gain electrons to form anions
- Example: F (4.0) > O (3.5) > Cl=N (3.0)
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Description
Learn about electron-deficient molecules, odd-electron molecules, and expanded valence shells in chemistry. Understand the characteristics of these molecules with examples.
