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Questions and Answers
Which of the following best describes the electronegativity trend on the periodic table?
Which of the following best describes the electronegativity trend on the periodic table?
What type of bond is formed when electrons are equally shared between two non-metal atoms?
What type of bond is formed when electrons are equally shared between two non-metal atoms?
In a molecule of water (H₂O), what type of charges are present on the atoms due to unequal sharing of electrons?
In a molecule of water (H₂O), what type of charges are present on the atoms due to unequal sharing of electrons?
What range of electronegativity difference typically indicates a polar covalent bond?
What range of electronegativity difference typically indicates a polar covalent bond?
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Which of the following is NOT a factor in determining the type of bond formed between two atoms?
Which of the following is NOT a factor in determining the type of bond formed between two atoms?
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What does a dipole moment indicate in a molecule?
What does a dipole moment indicate in a molecule?
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Why does oxygen have a partial negative charge in water?
Why does oxygen have a partial negative charge in water?
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Which of these is the best example of molecule with a pure covalent bond?
Which of these is the best example of molecule with a pure covalent bond?
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What is the primary difference between electron geometry and molecular geometry?
What is the primary difference between electron geometry and molecular geometry?
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What causes a water molecule to have a bent shape rather than a linear shape?
What causes a water molecule to have a bent shape rather than a linear shape?
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Which condition must a molecule meet to be considered polar?
Which condition must a molecule meet to be considered polar?
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What characteristic of carbon dioxide makes it non-polar despite having polar bonds?
What characteristic of carbon dioxide makes it non-polar despite having polar bonds?
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Based on the table, which of the following molecules is most likely to be non-polar?
Based on the table, which of the following molecules is most likely to be non-polar?
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If a diatomic molecule has two different elements, what is the most likely polarity of the molecule?
If a diatomic molecule has two different elements, what is the most likely polarity of the molecule?
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Given a molecule with the formula AB₃, where A is nitrogen, the molecule's polarity would most likely be considered:
Given a molecule with the formula AB₃, where A is nitrogen, the molecule's polarity would most likely be considered:
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What is the first step in determining if a molecule will be polar?
What is the first step in determining if a molecule will be polar?
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Study Notes
Determining Bond and Molecular Polarity
- Electronegativity (EN) is a measure of an atom's ability to attract shared electrons in a chemical bond.
- Ionic bonds involve the transfer of electrons between a metal and a non-metal, with electronegativity differences greater than 1.7.
- Polar covalent bonds involve unequal sharing of electrons between atoms with electronegativity differences between 0.4 and 1.7.
- Pure (nonpolar) covalent bonds involve equal sharing of electrons between two nonmetals, with electronegativity differences of 0.
- Examples: NaCl (ionic), H₂O (polar covalent), O₂ (nonpolar covalent)
Electronegativity Trends
- Electronegativity generally increases across a period (left to right) on the periodic table and decreases down a group (top to bottom).
- Electronegativity is not measured but rather determined based on EN values being compared
- High values of electronegativity mean the atom pulls electrons towards itself more readily
- Low values of electronegativity mean the atom allows other atoms to pull more of the electrons towards itself
Polar Covalent Bonds
- Polar covalent bonds occur when one atom has a stronger affinity for electrons than the other.
- This results in an uneven distribution of charge, with the atom with higher EN having a partial negative charge (δ−) and the atom with lower EN having a partial positive charge (δ+).
- A good example is seen in a hydrogen chloride (HCl) molecule
- Polar bonds can affect the polarity of the entire molecule
Molecular Polarity
- A molecule is polar if it contains polar bonds and the molecule is asymmetrical.
- Symmetrical shapes result in cancellation of partial charges
- Asymmetrical shapes don't have canceling charges (i.e. dipole moment). The shape of the molecule needs to be taken into consideration when determining polarity.
- Examples of polar molecules include water (H₂O), ammonia (NH₃), and hydrogen chloride (HCl).
- Examples of nonpolar molecules include carbon dioxide (CO₂), oxygen (O₂), and methane (CH₄).
Molecular Shapes
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Molecular shapes are determined by the arrangement of atoms and lone pairs of electrons around a central atom. Valence shell electron pair repulsion (VSEPR) theory is used to predict these shapes.
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Examples include:
- Linear
- Trigonal planar
- Bent/Angular
- Tetrahedral
- Trigonal pyramidal
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Water is a bent molecule because of the two lone pairs of electrons on the oxygen atom which affect the bond angles and produce a dipole moment.
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Carbon dioxide is linear, meaning the molecule is straight, which leads to the cancellation of the polar bonds and results in nonpolarity.
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Description
This quiz delves into the concepts of bond and molecular polarity, focusing on electronegativity and types of chemical bonds. Explore ionic, polar covalent, and nonpolar covalent bonds through examples and trends presented. Test your understanding of how electronegativity influences molecular polarity.
