Chemical Interactions and Electronegativity

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Questions and Answers

Which molecule is an example of having an odd number of electrons?

BF₃

H₂O

ClO₂ (correct)

PCl₅

Which statement describes a situation where an atom has fewer than eight electrons?

NO₂ has a full octet around nitrogen.

NH₄⁺ has eight electrons surrounding nitrogen.

BF₃ has six electrons around the boron atom. (correct)

PCl₅ possesses an expanded octet.

What is a defining feature of molecules with more than an octet?

They must have unpaired electrons.

They always form ionic bonds.

They contain atoms with fewer than four valence electrons.

They can have up to ten valence electrons in the outer shell. (correct)

Which of the following correctly identifies a limitation of the octet rule?

It does not account for the presence of transition metals. (C) Signup and view all the answers

What electronic configuration does hydrogen achieve when it shares electrons in NH₃?

Helium configuration (B) Signup and view all the answers

What is the primary driving force for chemical interactions between atoms?

Coulombic attraction and repulsion forces (C) Signup and view all the answers

What happens when the overlapping orbitals have the same sign?

There is a positive overlap (C) Signup and view all the answers

Which of the following statements is correct regarding the stability of the H₂+ ion?

It is more stable than H + H+ (A) Signup and view all the answers

What does zero overlap of orbitals result in?

Repulsion between the atomic nuclei (C) Signup and view all the answers

How does increased electron density affect the interaction between two nuclei?

It enhances attraction of both nuclei for electrons (C) Signup and view all the answers

Which expression correctly characterizes the interaction when there is negative overlap?

The net repulsion increases (C) Signup and view all the answers

What is the effect of overlapping orbitals on the electron density between atomic cores?

It results in higher electron density than separate orbitals (C) Signup and view all the answers

What occurs when two orbitals overlap with opposite signs?

Negative overlap resulting in repulsion (D) Signup and view all the answers

What phenomenon occurs when the net overlap of electron density is zero?

Non-bonding interaction (B) Signup and view all the answers

What does Pauling's definition of electronegativity focus on?

Difference between two atoms' electronegativities (B) Signup and view all the answers

According to Pauling, an electronegativity difference greater than 1.7 indicates which of the following?

More ionic character of the bond (D) Signup and view all the answers

How is Robert Mulliken's definition of electronegativity characterized?

As the average value of ionization energy and electron affinity (C) Signup and view all the answers

Which statement about electronegativity is true regarding elements close to fluorine?

They possess high Mulliken electronegativities (B) Signup and view all the answers

What is described as the octet rule?

Atoms achieve eight electrons in their valence shell (D) Signup and view all the answers

What aspect of electronegativity is emphasized by A.L. Allred and E. Rochow's definition?

The effect of the electric field at the atom's surface (C) Signup and view all the answers

What application of electronegativity involves understanding the polarity of molecules?

Rationalizing types of reactions (D) Signup and view all the answers

Study Notes

Driving Forces for Chemical Interactions

Coulombic attraction and repulsion forces between the nucleus and electrons of two or more atoms cause chemical interactions.
Chemical interactions occur when the outer orbitals of different atoms overlap, concentrating electron density between the atomic cores.
Positive overlap increases electron density between the atomic cores resulting in a stronger attractive force.
Negative overlap reduces electron density between the atomic cores leading to a repulsive force.
Zero overlap results in a non-bonding interaction as there is neither attraction nor repulsion between the atoms.

Electronegativity

Electronegativity refers to the power of an atom of an element to attract electrons in a compound.
Pauling's electronegativity difference between two atoms is 0.180 Δ, where Δ is the resonance energy in kcal/mol, calculated from bond energy difference.
A difference in electronegativity smaller than 1.7 indicates a covalent bond, while a difference greater than 1.7 indicates an ionic bond.
Mulliken's electronegativity, Xm, is the average of the ionization energy and electron affinity.
Allred and Rochow calculated electronegativity based on the electric field at the surface of an atom, using the effective nuclear charge and covalent radius.

Applications of Electronegativity

Electronegativity can be used to understand bond energies, predict the polarity of bonds and molecules, and rationalize the types of chemical reactions.

Octet Rule

Atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons in their valence shell.
This rule applies mostly to representative elements but has exceptions.

Exceptions to the Octet Rule

Odd Number of Electrons: Molecules like NO or ClO₂ with an odd number of electrons can't achieve complete pairing and an octet around each atom.
Less than an Octet: Atoms like boron in BF₃ have less than eight electrons in their valence shell.
More than an Octet: Atoms like phosphorus in PCl₅ expand their valence shell to accommodate more than eight electrons.

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Description

Explore the driving forces behind chemical interactions, including Coulombic attraction and repulsion. Delve into the concept of electronegativity and its role in bond formation, focusing on the implications of electron density in atomic interactions.