Polarity: Bonds and Molecule

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Electronegativity is the measure of the ability of an atom in a bond to attract electrons to itself.Electronegativity increases across a period and decreases down a group.

Review of Electronegativity

• Types of Boding:

• Convalent Bond
• Nonpolar Covalent
• Polar Covalent
• Ionic Bond

The chemical bonding behavior of elements is significantly influenced by electronegativity. The differential electronegativity between two interacting atoms controls the nature of the resulting bond. A large electronegativity difference results in a mostly ionic bond, while a small electrongativity differnce results in a covalent bond.

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Electronegativity in Bonding

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Example: H2, 02, Cl2

Nonpolar Covalent bonds are a type of chemical bond formed between two atoms when they share electrons almost equally. This equal sharing results in no significant separation of electrical charge within the molecule. Electrons within a nonpolar covalent bond have equal probability of being near the nucleus of each atom in the bond.

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Polar Covalent bonds are a type of chemical bond formed between two atoms where the electrons are shared, but the sharing is unequal. This unequal sharing is a result of electrons being more attracted to one atom over another (electronegativity). Polar covalent bonds are characterized by a partial positive charge on one atom while the other now has a partial negative charge. This is known as a dipole.

Covalent Bonds

Dipole

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Dipole

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A dipole is a molecule with a permanent separation of electrical charge. This separation arises when atoms within the molecule share electrons unequally due to differences in their electronegativity. A dipole moment is the measure of the polarity of the molecule. Dipoles go from the slightly positive charged (δ+) atom to the slightly negative charged atom(δ−). This is indicated by an arrow.

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Electronegativity table

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Bond Polarity

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Individual atoms within a polar molecule can have a partial positive charge (δ+) and while the other atom will with a partial negative charge (δ–). An entire molecule may also have a separation of charge depending on the molecular shape and polarity of the overall bonds.

In general, symmetrical molecules are non-polar because dipoles cancel and asymmetrical molecules are polar because they do not cancel.

If all bonds are non-polar, the molecule is automatically non-polar. If some or all bonds are polar, you have to look at the shape of the module.

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Polar Molecules

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Solution

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Solution

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Reminder of the Octet Rule

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Ionic bonds are a type of chemical bond that occurs when there is an electrostatic attraction between two atoms. The bond occurs when the valence electron of one atom is transferred to the other, allowing both to possibly fulfill the Octet Rule. That atom receiving the electron(s) is given a negative charge and the atom losing the electron becomes positively charged.

Ionic Bonds

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When atoms form an ionic bond, this means electrons are moved from one atom to another. The Proton never leaves the atom.

Types of ions: There are two main types:

• Cations: Positively charged ions (e.g., Na+, Ca2+).
• Anions: Negatively charged ions (e.g., Cl-, SO42-).

An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net positive or negative electrical charge.

What is an Ion?

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bond formed from an sharing of electrons. 2

a dipole forms between the atoms in the bond. 4

valence electron(s) are either lost or gained by an atom forming a positive or negative charge. 3

Drag each infromation to the drawer of the corresponding concept

bond formed from an electrostatic attraction between two atoms. 1

2 & 4

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1 & 3

Covalent Bonds

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Ionic Bonds

Solution

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“Electronegativity and Bonding: Chemical Bonds: Chemistry: Khan Academy.” YouTube, 29 Oct. 2013, youtu.be/126N4hox9YA?si=rI3n4vLCtKYrLF4i. Accessed 08 Feb. 2024.

Clark, Adelaide E. General Chemistry II. Open Oregon Educational Resources, 2019.

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Attributions

a dipole is a molecule with a permanent separation of electrical charge. This separation arises when atoms within the molecule share electrons unequally due to differences in their electronegativity. A dipole moment is the measure of the polarity of the molecule.

Dipoles are often shown with the positive and negative atoms in a polar covalent bond using a lowercase Greek letter “delta,”δ, with a plus sign or minus sign to indicate whether the atom has a partial positive charge (δ+) or a partial negative charge (δ−).

Dipole:

Example of a Cation:

NH3 is considered a polar molecule because a dipole moment occurs between the slightly more electronegative nitrogen atom and the three hydrogens. There is an asymmetrical shape between the pair electrons of nitrogen and the three hydrogens.

Electronagtivity Difference Chart and the Pauling Scale for Electronegativity

CCl4 is nonpolar because the chlorine atoms are arranged in a way that the electrical charge from each individual atom is canceled out by the other.

The octet rule is a guide that explains how atoms tend to bond with each other. It states that atoms generally achieve stability (nuetral charge) by having eight electrons in their outermost energy level (valence shell), similar to the electronic configuration of noble gases. This stability arises from a filled or closed-shell configuration, which lowers the atom's potential energy.

Octet Rule

Example of an Anion:

CH3ClPolar molecule: asymmetrical

CO2Nonpolar molecule: symmetrical