Chemistry Chapter 6, Section 1 Review

Describe the potential energy of two atoms that have formed a covalent bond.

Lowest potential energy.

What are some common properties of metallic bonds?

Metallic bonds are conductors of electric current as a solid, generally malleable and ductile.

Triangle

"Change to"

How are partial charges represented?

"Delta"

How are electronegativity differences related to bond strength?

"Directly related", greater electronegativity differences tend to be associated with stronger bonds.

How are electronegativity differences related to polarity?

"Directly related", the greater the difference between the electronegativity values of two elements joined by a bond, the greater the polarity of the bond.

How are stability and potential energy related when referring to compounds?

"Inversely Related", Unbonded atoms have a relatively low stability and a high amount of potential energy due to the energy released when a compound is formed.

What is a "diatomic molecule"? Give an example.

2 atoms joined together by covalent bonds, H2.

What is meant by the following statement: "The potential energy of H2 is -436 kJ/mol at a bond length of 75 pm"?

436kJ of energy is released when 1 mol of bonds form. It also means that 436kJ of energy must be supplied to break the bonds and separate the hydrogen atoms in 1 mol of H2 molecules.

Define "covalent bond".

A bond formed when atoms share one or more pairs of electrons.

Define "nonpolar covalent bond".

A bond in which the bonding electrons are shared equally.

Define "polar covalent bond".

A covalent bond in which a shared pair of electrons are not equally attracted to both bonded atoms.

What occurs when the forces of attraction and repulsion are balanced?

A covalent bond is formed where electrons are shared.

Define "dipole".

A molecule or part of a molecule that contains both positively and negatively charged regions.

What occurs when electronegativity values are not the same between two atoms?

A polar covalent bond will form in which electrons will not be shared equally.

Rather than thinking of bonds as "rigid sticks", what is a more accurate representation of covalent bonds? Why is this representation more accurate?

A spring is a more accurate representation of covalent bonds. In a covalent bond the two nuclei vibrate back and forth, causing the distance to constantly change much like a spring.

Describe the boundaries between bond types.

Due to the boundaries not being distinct, they are arbitrary.

What property is used to determine how the bond will form?

Electronegativity.

What is released as potential energy decreases?

Energy.

If two atoms with different electronegativities form a covalent bond, where are the shared electrons more likely to be found?

Found near the atom with higher electronegativity.

Provide an example of a molecule that has a nonpolar covalent bond.

H2 molecule.

Provide an example of a molecule that has a polar covalent bond.

HF, H2O, CO.

When does an ionic bond form?

Ionic bond forms from oppositely charged ions.

What are some common properties of ionic bonds?

Ionic bounds are good conductors of electric current when dissolved or melted in water, hard, brittle, and has high melting and boiling points.

Between what types of elements do ionic bonds tend to form?

Metals and nonmetals.

Describe the stability of most individual atoms. Why are noble gases the exception?

Most individuals have relatively low stabilities, aside from noble gases. Noble gases are the exception due to having a full outer valence shell.

The difference in electronegativity between C and Col is 0.6, and the difference in electronegativity between Al and Cl is 1.6. Which covalent bond is more polar? Why?

The covalent bond that is more polar is between Al and Cl because the bond between these two elements is more polar, with greater potential charges, and a greater difference in electronegativity values.

Define "ionic character".

The degree to which a compound has properties similar to an ionic compound.

What causes the difference in properties between bonds?

The differences in strength of attraction between atoms causes the differences in properties.

Define "bond length".

The distance between two bonded atoms at their minimum potential energy; the average distance between the nuclei of the two bonded atoms.

VSEPR

Valence Shell Electron Pair Repulsion. A concept of chemical bonding that is based on the idea that valence electrons repel each other. Used to predict molecular shape, requires a lewis structure, and shape determined influeces polarity; polarity influences properties.

"Lone electrons"

non-bonding

Define "molecular orbital".

Space surrounding the nuclei where electrons move.

What is the general relationship between bond strength and bond length?

Stronger bonds generally have shorter bond lengths.

Describe the stability of a H2 molecule compared to that of individual (not bonded) hydrogen atoms. Why is one more stable than the other?

The H2 molecule is more stable than either hydrogen atom by itself. The H2 molecule is stable because each hydrogen atom has a shared pair of electrons. This pair gives both atoms a helium configuration stability, having filled orbitals.

What often occurs when covalent bonds form between two different atoms?

Different attractions for electrons which means electrons may not be shared equally.

What are some common properties of covalent bonds?

Covalent bonds are not good conductors of electric current with low melting and boiling points.

How does potential energy change as forces of attraction pulls two atoms closer together?

Decreases as atoms draw closer together and bond.

Between what types of elements do covalent bonds tend to form?

Nonmetals.

How can differences in electronegativity help determine bond type?

Nonpolar covalent (0-.5) are even electron distribution, polar covalent (.5-2.1) are uneven electrons distribution, and ionic (2.1-3.3) are separate electron clouds.

Differentiate between a polar covalent bond and an ionic bond.

Polar: Electrons unequally shared (atoms), Ionic: Electrons transferred forming ions, attraction of opposite charged ions.

When hydrogen and oxygen join to form water, what happens to the electrons?

The electrons are shared between neutral atoms.

Describe the distribution of charges for a polar covalent compound, such as HF. WHy does the distribution of charge occur?

The ends of HF molecule have opposite partial charges. The electronegativity of F (4.0) is higher than H (2.2) therefore, the shared electrons will be found closer to F, causing a partial negative charge. H will form a partial positive charge.

Define "bond energy".

The energy required to break the bonds in 1 mol of a chemical compound.

How are electronegativity differences related to ionic character?

The larger electronegativity difference, the higher the percentage of ionic character between to bond.

Describe the effect that rigid covalent bonds would have on the distance between nuclei.

The nuclei of the bonded atoms would be at a fixed distance from each other.

Illustrate the forces of attraction and repulsion between two hydrogen atoms.

The nucleus of each atom attracts both electron clouds. Both nuclei repel each other, as do both electron clouds. Like repel, opposite attract.

What does the word "polar" suggest about a bond?

The word polar suggests that this bond has ends that are in some way opposite of one another, like the two poles of a planet, a magnet, or a battery.

What happens to the electrons in an ionic bond?

Transferred from one atom to another forming ions.

Besides electronegativity, what other methods could be used to classify bonds?

You can also classify bonds by looking at the characteristics of the substance.