Unit 9 chemistry

The Lewis structure for the nitronium ion is shown. The formal charge on the N atom is equal to _____ and the formal charge on each O atom is equal to _____.

+1; 0

Consider the equations shown. Use the Born-Haber cycle to estimate the lattice energy of lithium chloride (LiCl).

+862 kJ/mol

The Lewis structure for the cyanide ion is shown. The formal charge on the C atom is equal to _____ and the formal charge on the N atom is equal to _____.

-1; 0

Consider the formation of an ionic bond between the elements potassium (K) and chlorine (Cl). Which of the following statements describe this process correctly? Select all that apply.

-Total number of electrons lost equals the total number of electrons gained -K loses one electron from its 4s orbital to form a K+ cation -Both the K+ and Cl- ions have full outer shells containing 8 electrons

The octet rule states that an atom other than hydrogen tends to form bonds until it is surrounded by valence electrons.

8

Which of the following Lewis symbols correctly represent the element shown? Select all that apply.

:S····:S···· ·B·.·B·. ·H·H

Taking into account formal charges, which of the following Lewis structures is the most plausible for phosgene (COCl2)?

A

Which of the following Lewis structures correctly represents the structure of formaldehyde (CH2O)?

A

Which of the following Lewis structures correctly represents the structure of suflur dioxide (SO2)?

A

Which of the following Lewis structures is the most plausible Lewis structure for hydrogen cyanide (formal charges may have been deliberately omitted)?

A

Which of the following statements correctly describe a polar covalent bond? Select all that apply.

A bond between atoms whose electronegativities differ, but by less than 2.0, is polar covalent. In a polar covalent bond, the electron density is highest over the more electronegative atom.

Which of the following statements correctly describe a coordinate covalent bond? Select all that apply.

A coordinate covalent bond is a covalent bond formed between two atoms where one of the atoms donates both of the bonding electrons. A coordinate covalent bond is also known as a dative bond.

Which of the following statements correctly describes a covalent compound?

A covalent compound contains only covalent bonds.

Which statement about a polar covalent bond is correct?

A polar covalent bond involves unequal sharing of electrons.

Which of the following options correctly describe the guidelines used to select the most plausible Lewis structure for a given covalent species? Select all that apply.

A structure with smaller formal charges on individual atoms is preferred. A structure is more stable if a negative charge resides on a more electronegative atom.

Which of the following statements correctly describe the reaction represented by the equation shown? Select all that apply.

A total of six valence electrons are being transferred. The electron configuration of S2- is 1s22s22p63s23p6.

Which of the following are plausible resonance structures for hydrogen cyanide (HCN)?

AD

Which of the following statements correctly describe ionic bonding? Select all that apply.

An ionic bond is the electrostatic attraction between two oppositely charged ions. Ionic bonding involves the transfer of electrons from the metal to the nonmetal.

Which of the statements below correctly describe an ionic bond? Select all that apply.

An ionic bond typically forms in a compound between a metal and nonmetal. An ionic bond is the electrostatic force that holds ions together in an ionic compound.

Which of the following are plausible resonance structures for nitrite anion (NO2-)?

B C

is a measure of the tendency of an atom to attract shared electrons to itself in a covalent bond.

Blank 1: Electronegativity

Most covalently bonded substances consist of individual separate molecules. Each individual molecule is held together by means of strong bonds between the atoms. In addition, there are weak forces of attraction between the individual molecules, called forces.

Blank 1: covalent, intramolecular, or localized Blank 2: intermolecular, van der Waals, or weak intermolecular

Lewis structures are used to represent covalent compounds. Shared electron pairs are shown either as pairs of or lines and only electrons are shown.

Blank 1: dots Blank 2: valence, outer, or outermost

For two Lewis structure forms with the same formal charges, the structure that has the negative formal charge on the more atom will be preferred.

Blank 1: electronegative

The electronegativity of the elements when moving from left to right across a period of the periodic table, while electronegativity when moving down a group.

Blank 1: increases, grows, gets larger, or gets bigger Blank 2: decreases, shrinks, gets smaller, or lessens

Lattice energy is defined as the energy required to completely separate one mole of a solid compound into gaseous .

Blank 1: ionic Blank 2: ions

Most covalent substances do not conduct electricity, even when melted or in solution. An electric current is carried by the movement of either electrons or . In covalent substances the electrons are localized either as pairs or as lone pairs, and no ions are present. Since there are no charged particles free to move, covalent substances are poor electrical conductors.

Blank 1: ions Blank 2: bonded, shared, bonding, or bond

When determining the total number of valence electrons in a polyatomic ion, one electron is added for every charge on the ion, and one electron is subtracted for every charge on the ion.

Blank 1: negative or minus Blank 2: positive or plus

The term means that at least two Lewis structures can be used to represent a particular covalent species. (Use only one word for your answer.)

Blank 1: resonance

A covalent bond is a bond in which two or more electrons are between two atoms. The covalent bond is often represented by a pair of dots or a .

Blank 1: shared Blank 2: line, dash, or single line

When two atoms form a triple bond, they share a total of electrons. When forming a single bond, they share a total of electrons.

Blank 1: six or 6 Blank 2: two or 2

An ionic compound does not conduct electricity in the state because the ions are held together by strong attractive forces and cannot move from their positions in the crystal structure. If the solid melts or dissolves in water, the ions are free to move and carry a(n) current.

Blank 1: solid or crystalline Blank 2: electric or electrical

The formal charge assigned to an atom is calculated by subtracting the number of electrons the atom "owns" from its total number of electrons. The number of electrons "owned" by a specific atom is defined as being the sum of the valence electrons and half the valence electrons.

Blank 1: valence or outer Blank 2: unshared, nonbonding, unbonded, nonbonded, lone, lone pair, non-bonded, or non-bonding Blank 3: shared, bonding, bond pair, or bonded

Which of the following elements, when covalently bonded, commonly have fewer than an octet of electrons with a formal charge of zero? Select all that apply.

Boron Beryllium

Which of the following Lewis structures correctly represents the structure of dichloromethane (CH2Cl2)?

C

Which of the following Lewis symbols correctly represent that element? Select all that apply.

C··· ·N····

Which of the following statements correctly describe a Lewis dot symbol? Select all that apply.

Each dot in a Lewis dot symbol represents a valence electron. Elements in the same group have similar electron configurations and hence similar Lewis dot symbols.

Which of the following statements correctly describe how the Born-Haber cycle may be used to determine the lattice energy? Select all that apply.

Each step in the Born-Haber cycle relates to energy changes for a mole of atoms/ions. The lattice energy has the same value (but opposite sign) as the enthalpy of formation of the ionic solid from a mole of gaseous ions. The Born-Haber cycle correctly defines the steps that precede the formation of an ionic solid. The energy of sublimation is used in Born-Haber cycle calculations.

Which of the following statements correctly describe electronegativity and electron affinity? Select all that apply.

Electronegativity is the ability of an atom to attract toward itself the electrons in a chemical bond. Atoms with a high electronegativity generally have high values of electron affinity.

Which of the following options correctly describe electronegativity? Select all that apply.

Electronegativity measures the ability of an atom in a covalent bond to attract the shared electron pair(s). Electronegativity is a relative quantity.

True or false: Resonance structures are different possible structures for the same species that interconvert rapidly.

F

Which of the following statements correctly describe how to calculate the total number of valence electrons for a polyatomic anion or cation? Select all that apply.

For each negative charge in the ion, add 1 to the total number of valence electrons of the atoms. For each positive charge in the ion, subtract 1 from the total number of valence electrons of the atoms. Count the total number of valence electrons for all atoms in the structure.

Which of the following statements correctly describe formal charge? Select all that apply.

Formal charges can be used to select the most important resonance structures for a species. The formal charge of an atom is the charge it would have if all bonding electrons were shared equally.

Which of the following are characteristic properties of ionic compounds? Select all that apply.

High melting points Nonconductors in the solid state

When are multiple bonds needed in a Lewis structure?

If one or more atoms do not have an octet of electron but all electrons have already been placed

Why does an ionic solid not conduct electricity in the solid state, but is a good conductor when melted or dissolved in water? Select all that apply.

In the liquid or dissolved state, the ions are free to move and can carry an electric current. In the solid state, the ions are held in specific positions and are not free to move.

A covalent species such as the molecule H3NO has more than one central atom. Which of the following options correctly describe how to draw a Lewis structure for this species? Select all that apply. Multiple select question.

N and O are central atoms because both elements form more than one covalent bond. There will be three bonds to the N atom. The O atom will be bonded to both H and N.

select all bonds that are polar covalent bonds.

N-B C-Cl B-Cl H-O C-N

Which of the following statements correctly describe trends in lattice energy? Select all that apply.

NaCl is expected to have a higher lattice energy than NaBr. The lattice energy of an ionic compound tends to decrease as ionic size increases.

Which of the following statements correctly reflect how to calculate the oxidation number of a covalently bonded atom using electronegativity? Select all that apply.

O.N. = (valence electrons) - (assigned shared electrons + unshared electrons) An atom in a bond is assigned all its unshared electrons.

The formation of an ionic bond involves a number of different processes. In the formation of sodium chloride, represented by the equation given below, which steps require an input of energy? Select all that apply. 2Na(s) + Cl2(g) → 2NaCl

Removal of an electron from Na Conversion of Na(s) → Na(g) Dissociation of Cl2 to form 2Cl

Which statement about resonance structures is NOT correct?

Resonance structures interconvert rapidly.

Structure B (as shown) is the most plausible Lewis structure for isocyanate ion (NCO-). Select the statements that would guide you to this conclusion.

Structure A is less stable than structure B as the negative formal charge is on a less electronegative atom in A. Structure C has a -2 formal charge on N. Structures bearing large formal charges are less stable than those with small formal charges. Structure A is less stable than structure B as the negative formal charge is on a more electronegative atom in B.

Structure C (shown) is the most plausible Lewis structure for the nitronium ion (NO2+). Select the statements that would guide you to this conclusion.

Structure B has formal charges on all three atoms, while structure C only has a formal charge on nitrogen. Structure A violates the octet rule.

Which of the following statements describe the Born-Haber cycle correctly? Select all that apply.

The Born-Haber cycle relates lattice energies to electron affinities. The Born-Haber cycle is based on Hess's law.

Which of the following statements correctly relate percent ionic character and electronegativity differences to the nature of a particular bond? Select all that apply.

The bond in NaF (electronegativity difference between the two atoms is 3.1) has a large percentage of ionic character. A chlorine-chlorine bond has 100% covalent character. A purely covalent bond has 0% ionic character.

Which of the following factors affect the magnitude of the lattice energy for an ionic compound? Select all that apply.

The charges of the ions The size of the ions

Which of the following statements correctly relate bond type to electronegativity? Select all that apply.

The hydrogen-chlorine bond is covalent. A covalent bond forms between two atoms that have an electronegativity difference of less than 2.0. An ionic bond forms between two atoms that have an electronegativity difference of 2.0 or more.

Many covalent compounds are gases, liquids, or low-melting solids at room temperature. Which option correctly accounts for this behavior?

The intermolecular forces between the molecules require little energy to break.

Which statement below about covalent bonding is correct?

Two pairs of electrons are shared in a double bond.

Which of the following statements correctly describe the steps followed when drawing a Lewis structure? Select all that apply.

Valence electrons must be shown as lone pairs if they are not involved in bonding. In general, the least electronegative atom should occupy the central position in the Lewis structure. For polyatomic anions, add the number of negative charges to the total number of valence electrons.

Multiple bonds are typically introduced into a Lewis structure if the central atom does not have ______ once all of the valence electrons are placed.

a full octet

For the purpose of calculating formal charge in a Lewis structure, an atom is assigned ______ of the nonbonding electrons in its valence shell, and ______ of the bonding electrons in its valence shell.

all; half

Resonance structures are Lewis structures that have the same relative placement of _____ but a different arrangement of _____.

atoms; electrons

Intermolecular forces are ______ forces between molecules.

attractive

The distance between the nuclei of two covalently bonded atoms is the _____.

bond length

Intermolecular forces ______.

cause molecules to be attracted to each other

A chemical bond that arises from the sharing of two or more electrons between two atoms is called a(n) ______ bond.

covalent

______ compounds are compounds that form from the sharing of electrons between atoms.

covalent

The bond formed between two nonmetals, which are usually very similar in their tendency to lose or gain electrons, is the bond. This bond involves the of one or more electron pairs between the two atoms.

covalent, sharing

Consider the periodic trends in electronegativity in comparison with trends in metallic character. Electronegativity ______ as metallic character increases, and ______ as metallic character decreases.

decreases; increases

A water-soluble ionic compound is classed as a(n) ______, because it produces ______ ions when dissolved in water.

electrolyte; many

The ability of an atom of a given element to attract shared electrons to itself in a covalent bond is called ______.

electronegativity

The charge difference between the number of valence electrons in a neutral atom and the number of valence electrons assigned to that atom in a Lewis structure is called the ______.

formal charge

As a consequence of Coulomb's law, a generic compound MX formed from M2+ and X2- will have a ______ lattice energy than a generic compound MX formed from M+ and X-.

greater

Consider two ions whose charges have the same sign. According to Coulomb's law, the potential energy of the system will ______ as the two ions are brought closer together. Conversely, bringing two ions of opposite charges closer together will ______ the potential energy of the system.

increase; decrease

The lattice energy of an ionic solid is a measure of the attraction between the oppositely charged ions. As ionic charge increases, the attraction between the ions _____ and so does lattice energy. As the size of the ions increases, the attraction between the ions _____ and so does lattice energy. Lattice energy therefore _____ down a group of the periodic table and _____ across a period.

increases; decreases; decreases; increases

A chemical bond resulting from the electrostatic attraction between oppositely charged particles is called a(n) bond.

ionic

The electrostatic force that holds ions together is called a(n) _____ bond.

ionic

The bond typically observed when a metal bonds to a nonmetal is the _____ bond. The metal atom _____ one or more valence electrons while the nonmetal _____ electrons.

ionic; loses; gains

The Born-Haber cycle relates the _____ energies of ionic compounds to ionization energies and electron affinities.

lattice

The energy required to completely separate one mole of a solid ionic compound into gaseous ions is called the ______ energy.

lattice

A quantitative measure of the stability of an ionic compound is its ______.

lattice energy

A double bond between a given pair of atoms will be ______ than a triple bond, and ______ than a single bond.

longer; shorter

An ideal Lewis structure would be one in which ______ atom(s) bear formal charges. A Lewis structure with ______ formal charges is least preferred.

no; large

In the Cl2 molecule shown, the electron pair marked A is a ______ pair, while the electron pair marked B is a ______ pair.

nonbonding; bonding

Bond length is the distance between the ______ of two covalently bonded atoms.

nucelui

The formation of an ionic compound involves the transfer of electrons. The removal of one or more electrons from a metal is a process that _____ energy, whereas the addition of one or more electrons to a nonmetal _____ energy. Multiple choice question. requires an input of; releases

requires an input of; releases

______ is the use of two or more valid Lewis structures to accurately depict a given molecule.

resonance

Two or more Lewis structures that differ only by the placement of their electrons are known as ______.

resonance structures

Covalent bonding involves the ______ of electrons.

sharing

For a given pair of atoms, a triple bond is _____ than a double bond.

shortere

Melting an ionic solid involves freeing the ions from their positions in the ionic crystal and separating them. Since the ions are held together by _____ electrostatic attractions the amount of energy required is _____ and ionic solids therefore have relatively _____ melting points.

strong; large; high

The tendency of an atom in covalent bonding to surround itself with eight valence electrons is known as ______.

the octet rule

According to Coulomb's law the potential energy (E) between two ions is directly proportional to _____.

the product of their charges

An ionic bond forms as the result of the ______ of electrons.

transfer

Lewis dot structures are used to keep track of the total number of electrons in a chemical reaction.

valence

In a Lewis dot symbol, each dot represents a ______.

valence electron