Chemical Bonds and Lewis Structures

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Questions and Answers

What happens to the bond length as the number of bonds between two carbon atoms increases?

The bond length decreases as the bonds become stronger (correct)

The bond length increases due to less electron sharing

The bond length becomes unpredictable

The bond length remains the same regardless of the number of bonds

Which statement best describes a dative bond?

Dative bonds cannot involve lone pairs of electrons

The pair of shared electrons is supplied by one of the two bonded atoms (correct)

Dative bonds can only be formed between identical atoms

Both atoms contribute equally to the shared electrons

What characterizes a double bond between two atoms?

Sharing three pairs of electrons

Sharing one pair of electrons

Complete electron transfer from one atom to another

Sharing two pairs of electrons (correct)

Which of the following is true about triple bonds?

They occur when two atoms share three pairs of electrons Signup and view all the answers

Which condition is necessary for the formation of a dative bond?

The donor atom must have at least one lone pair of electrons Signup and view all the answers

What type of bond is formed between nitrogen and hydrogen in the ammonium ion?

Dative bond Signup and view all the answers

When drawing the Lewis structure for water, which atom is placed in the center?

Oxygen Signup and view all the answers

How many total valence electrons are present in methane (CH4)?

8 Signup and view all the answers

Which is the first step in writing Lewis structures?

Count total number of valence electrons Signup and view all the answers

What is one of the requirements for a molecule or ion to have a resonance structure?

It must have multiple bonds Signup and view all the answers

Which pair of elements is often assigned as the central atom in a Lewis structure?

The least electronegative element Signup and view all the answers

Which statement is true about formal charges?

A formal negative charge can exist on a more electropositive atom. Signup and view all the answers

What shape should be expected for a molecule with the formula COCl2?

Trigonal planar Signup and view all the answers

Which of the following molecules can have an incomplete octet?

Boron trifluoride (BF3) Signup and view all the answers

In Lewis structures, what is typically true of polyatomic species?

They are usually clumped together Signup and view all the answers

Which of the following compounds can exhibit an expanded octet?

Sulfur hexafluoride (SF6) Signup and view all the answers

What action should be taken if a Lewis structure contains too many electrons?

Form double and triple bonds as needed Signup and view all the answers

What condition allows a molecule or ion to have a formal positive charge?

It must be on a more electropositive atom. Signup and view all the answers

Which of the following is an example of an odd electron species?

Nitric oxide (NO) Signup and view all the answers

In what case must a molecule have lone pair electrons?

To facilitate resonance structures Signup and view all the answers

Which of the following is a requirement for a molecule to have a resonance structure?

It must have at least one double bond Signup and view all the answers

What is the purpose of calculating formal charges in Lewis structures?

To find the most stable Lewis structure with charges closest to zero Signup and view all the answers

When constructing a Lewis structure, which atom type should typically be placed in the center?

The least electronegative atom Signup and view all the answers

What action should be taken when a Lewis structure has too many electrons after fulfilling the octet rule?

Form double or triple bonds with the central atom as needed Signup and view all the answers

What is the expected formal charge for a stable molecule?

As close to zero as possible for each atom Signup and view all the answers

In what scenario would an atom be assigned a formal charge greater than zero?

When it has more bonds than electrons Signup and view all the answers

What is the first step in writing a Lewis structure for a compound?

Draw the skeletal structure of the compound Signup and view all the answers

If a molecule has a positive charge, how is the formal charge calculated?

By counting one less electron for each positive charge Signup and view all the answers

Which option best describes the role of d orbitals in Lewis structure construction?

They allow for the potential of forming additional bonds Signup and view all the answers

What does the octet rule indicate about an atom's preferred electron configuration?

An atom prefers to have a full outer shell with 8 electrons. Signup and view all the answers

In the formation of NaCl, what happens to sodium's valence electron?

Sodium loses its valence electron to achieve a stable octet. Signup and view all the answers

What is the electron configuration of the Na+ ion?

1s2 2s2 2p6 Signup and view all the answers

What is the approximate electron configuration of Cl- ion?

1s2 2s2 2p6 3s2 3p6 Signup and view all the answers

What type of bond is formed between Na+ and Cl- ions?

Ionic bond Signup and view all the answers

Which of the following statements is true regarding covalent bonds?

Covalent bonds involve sharing electrons to achieve stability. Signup and view all the answers

Which element has an exception to the octet rule due to its electron capacity?

Hydrogen Signup and view all the answers

What happens to chlorine atoms when they form ionic compounds?

Chlorine accepts an electron to complete its octet. Signup and view all the answers

Study Notes

Bonds and Examples

Carbon monoxide (CO) features a coordinate bond between carbon (C) and oxygen (O).
Ammonium ion (NH4) forms when ammonia (NH3) gains a proton (H+).
Hydronium ion (H3O) results from water (H2O) accepting a proton.

Drawing Lewis Structures

Start by counting total valence electrons; add or subtract electrons based on ion charges.
Construct a skeletal structure connecting atoms with bonds.
Place the least electronegative element in the center of the structure.
Complete the octet for all atoms except hydrogen, which follows the duet rule.
If necessary, create double or triple bonds to accommodate too many electrons.

Octet Rule

Atoms seek to have 8 electrons in their highest energy level to achieve stability.
Sodium (Na+) loses one electron to achieve a stable octet, while Chlorine (Cl-) gains one.
Sodium chloride (NaCl) forms when sodium donates its valence electron to chlorine.

Types of Chemical Bonds

Ionic bonds occur via electrostatic attraction between positively and negatively charged ions.
Covalent bonds share electrons between atoms, including single, double, and triple bonds.
Hydrogen is a special case, only able to hold 2 electrons due to its position in the periodic table.

Bond Lengths

The bond length decreases as the number of bonds increases; for example, C-C bond lengths are:
- Single bond: 1.54 Å
- Double bond: 1.34 Å
- Triple bond: 1.20 Å

Dative Bonds

Dative (or coordinate) bonds occur when one atom donates both electrons for bonding.
For dative bonds, the donor must have a lone pair of electrons, and the acceptor should have an empty orbital.

Writing Lewis Structures Steps

Arrange remaining electrons to satisfy hydrogen's duet and other atoms' octets after forming initial bonds.
If insufficient electrons remain, employ d orbitals from Period 3 or beyond to expand octets.
If there are extra electrons, form multiple bonds as needed.

Formal Charge

Formal charge assesses the distribution of electrons in a Lewis structure, with the ideal being closest to zero.
The sum of formal charges should equal zero for neutral molecules or the overall charge for polyatomic ions.
A stable Lewis structure has minimal formal charges and negative charges on more electronegative atoms.

Resonance Structures

Molecules with multiple bonds and lone pairs can exhibit resonance.
Structures must have valid electron pair arrangements to describe resonance effectively.

Exceptions to the Octet Rule

Incomplete octets occur when central atoms possess fewer than 8 electrons, as seen in boron trifluoride (BF3).
Expanded octets are observed in elements like phosphorous and sulfur.
Odd-electron compounds, such as nitric oxide (NO), do not adhere to the octet rule.

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Description

This quiz covers the fundamental concepts of chemical bonds, including coordinate, ionic, and octet rule principles. It also delves into the process of drawing Lewis structures, providing a systematic approach to determining molecular connectivity. Test your knowledge on the examples and rules governing these essential topics in chemistry.