CHEM: Chapter 9

Which of the following statements correctly describe trends in lattice energy? -NaCl is expected to have a higher lattice energy than NaBr -NaCl should have a higher lattice energy than Na2O -the lattice energy of an ionic compound decreases as the charges on the ions increase -the lattice energy of an ionic compound tends to decrease as ionic size increases

-NaCl is expected to have a higher lattice energy than NaBr (since Br- is larger than Cl-, the lattice energy of NaBr will be lower) -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?

-Oxidation number = (valence electrons) - (assigned shared electrons + unshared electrons) -an atom is assigned all its unshared electrons

Coordinate covalent bon

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

Which of the following statements correctly describe resonance structures? -an individual resonance structure does not accurately represent the structure of the species -resonance structures are isomers of the same species -resonance structures differ only in the arrangement of electrons -resonance forms rapidly inter convert. The species could have nay one of the structures at any time

-an individual resonance structure does not accurately represent the structure of the species -resonance structures differ only in the arrangement of electrons

Which of the following statements correctly describe electronegativity and electron affinity? -electronegativity and EA are completely unrelated -atoms with a low electronegativity have a greater tendency to attract electrons than atoms with a high electronegativity -EA is the ability of an atom to attract toward itself the electrons in a chemical bond -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

-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 are characteristic properties of ionic compounds? -nonconductors in aqueous solutions -hard but flexible -high melting points -nonconductors in the solid state

-high melting points -nonconductors in the solid state

Match each type of bond with its correct description

-nonpolar covalent bond: equal distribution of electrons -polar covalent bond: unequal distribution of electrons -ionic bond: complete transfer of electrons

Resonance

-resonance is an invention designed to address limitations in simple bonding models -the properties of a molecule are best explained by the consideration of all possible resonance structures

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? -The N atom is bonded directly to O and to all three H atoms -The O atom will be bonded to both H and N -There will be three bonds to the N atom -H could be a central atom -N and O are central atoms because both form more than one covalent bond

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

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

-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 energy of sublimation is used in Born-Haber cycle calculations -the Born-Haber cycle correctly defines the steps that precede the formation of an ionic solid -each step in the Born-Haber cycle relates to energy changes for a mole of atoms/ions

Which of the following statements correctly describe a covalent bond? -the electron pair is attracted to only one of the nuclei -the shared pair of electrons is often represented by a single line -two electrons are shared between two atoms -two ions are held together by an electrostatic force

-the shared pair of electrons is often represented by a single line -two electrons are shared between two atoms

Which of the following factors affect the magnitude of the lattice energy for an ionic compound? -the total number of positive and negative ions present -the size of the ions -the charges of the ions -the number of valence electrons in the ions

-the size of the ions -the charges of the ions

Which of the following statements below correctly describe an ionic bond? -tends to form between two elements that have high ionization energies -forms when two bonding atoms share electrons -typically forms in a compound between a metal and nonmetal -is the electrostatic force that holds ions together in an ionic compound

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

Basic steps for drawing Lewis structure:

1. Draw the skeletal structure of the compound 2. Count the total number of valence electrons. If negative charges are present, add them to the total. If positive charges are present, subtract them. 3. Draw a single bond between the central atom and each of the surrounding atoms. Complete the octets of the atoms bonded to the central atom 4. If the central atom has fewer than 8 electrons, add double/triple bonds to the central atom, using lone pairs on outer atoms to complete the octet.

When the elements Mg and Cl form an ionic bond, Mg loses ____ electron(s) from the 3s orbital to form the Mg2+ cation. Cl gains _____ electron(s) in the 3p orbital to form the Cl- anion. Since the total number of electrons lost always equals the total number of electrons gained, the compound formed will contain ____ Mg2+ ion(s) for every _____ Cl- ion(s).

2; 1; 1; 2

An ionic bond exists between __________

A positively charged particle and a negatively charged particle

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

A covalent compound is a compound that contains only covalent ________

Bonds

Certain molecules are electron deficient, having fewer than 8 electrons around the central atom. Elements that commonly form electron deficient compounds are beryllium and ______

Boron

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

Covalent

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.

Covalent; intermolecular

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

Coulomb's law states that the potential energetic (E) between two ions is _______ proportional to the product of their charges and _________ proportional to the distance between them.

Directly; inversely

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

Dots; valence

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

Eight

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

Electronegativity

Ionic bond

Electrostatic force that holds ions together in an ionic compound

A Lewis dot symbol consists of the symbol of the _______ and one dot for each outer (valence) ___________ in an atom of the element.

Element; electron

Bond __________ is a measure of the energy required to break a particular bond in one mole of gaseous molecules.

Enthalpy

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

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

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

Increase; decreases

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

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

Ionic; 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.

Ions; bond

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

Lattice

Bond _______ is defined as the distance between the nuclei of two _________ bonded atoms in a molecule

Length; covalently

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

No; large

Some covalently bonded species do not obey the octet rule because they have an odd number of electrons. A species containing one ______ electron is called a radical. Many radicals are highly reactive and tend to form a(n) _________ bond with an unpaired electron on another molecule.

Odd; covalent

Lone pair of electrons

Pair of electrons that is localized on one atom

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

Resonance structures

An ionic compound does not conduct electricity in the _________ 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

Solid; electrical

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

Strong; large; high

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 electrons in an atom are primarily responsible for its behavior in chemical bonding?

Valence electrons

bonding pair of electrons

electrons that are shared between two atoms