Chemistry: Bond and Molecular Polarity

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Questions and Answers

What type of bond is formed when electrons are unequally shared between two atoms?

Metallic bond

Polar covalent bond (correct)

Pure covalent bond

Ionic bond

Electronegativity increases as you move down a group on the periodic table.

False

What does a dipole moment measure?

The polarity of a molecule

In a water molecule, oxygen has a partial ______ charge.

negative Signup and view all the answers

If the electronegativity difference between two atoms is 0, what type of bond is likely to form?

Pure covalent bond Signup and view all the answers

The atomic radius increases as you move across a period on the periodic table.

False Signup and view all the answers

What is the molecular geometry of a water molecule?

Bent Signup and view all the answers

Match the following bond types with their descriptions:

Ionic = Transfer of electrons Polar Covalent = Unequal sharing of electrons Pure Covalent = Equal sharing of electrons Signup and view all the answers

A molecule with only non-polar covalent bonds will always be a polar molecule.

False Signup and view all the answers

What causes the unique properties of water, such as its high boiling point?

The dipole moment due to polar H-O bonds Signup and view all the answers

What two criteria must be met for a molecule to be considered polar?

The molecule must contain polar bonds and be asymmetrical. Signup and view all the answers

The electron geometry describes the arrangement of all electron areas around a central atom, including bonding and ______ pairs.

lone Signup and view all the answers

Match the following molecular shapes with their descriptions:

Linear = Atoms are arranged in a straight line Bent = Two bonding pairs and two lone pairs contribute Tetrahedral = Four bonding pairs around the central atom Trigonal planar = Three bonding pairs around the central atom Signup and view all the answers

According to the rules, which of these molecules is non-polar?

CH4 Signup and view all the answers

The carbon-oxygen bond in carbon dioxide is considered non-polar.

False Signup and view all the answers

What causes the opposing dipoles in carbon dioxide to cancel out, making the molecule non-polar?

The linear shape of the molecule. Signup and view all the answers

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 non-metal. Electronegativity difference is greater than 1.7. Example: NaCl.
Polar covalent bonds involve unequal sharing of electrons between two nonmetals. Electronegativity difference is between 0.4 and 1.7. Example: H₂O.
Pure (non-polar) covalent bonds involve equal sharing of electrons between two nonmetals. Electronegativity difference is 0. Example: O₂.

Electronegativity Trends

Electronegativity generally increases across a period (left to right) on the periodic table.
Electronegativity generally decreases down a group (top to bottom).
Fluorine (F) is the most electronegative element.
Francium (Fr) is the least electronegative element.

Polar Covalent Bonds

A polar covalent bond is formed when the bonding pair of electrons is unequally shared between two atoms because one atom has a stronger affinity for electrons.
The atom with the stronger electron affinity develops a partial negative charge (δ–).
The other atom develops a partial positive charge (δ+).
Example: In a hydrogen chloride (HCl) molecule, chlorine is more electronegative than hydrogen, attracting the shared electrons more strongly resulting in a δ– charge on chlorine and a δ+ charge on hydrogen.

Molecular Shapes and Polarity

The arrangement of atoms in a molecule, its molecular shape, determines if the molecule is polar or nonpolar.
If a molecule contains polar bonds but it is symmetrical, the polar bonds cancel each other out, and the molecule is nonpolar. Example: Carbon dioxide (CO₂).
If a molecule contains polar bonds and it is asymmetrical, the molecule is polar. Example: Water (H₂O).
Molecules with lone pairs around the central atom can also influence the molecular polarity, even with symmetrical arrangements of bonds.
Different molecular shapes result from the need to maximize the distances between electrons in a molecule.

Determining Molecular Polarity

A molecule is polar if it:
Contains polar bonds
Is asymmetrical in shape, and/or contains lone pairs.
In summary: Polar molecules have a positive and a negative end.

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Description

This quiz assesses your understanding of electronegativity, bond types, and molecular polarity. You'll explore topics such as ionic bonds, polar covalent bonds, and the trends in electronegativity across the periodic table. Test your mastery of these essential chemistry concepts!