Chem CH.6.2

The bond length of a hydrogen-hydrogen bond is _____.

75 pm

As shown in Figure 6.2.3, the approaching nuclei and electrons are _____ to each other, which corresponds to a _____ in the total potential energy of the atoms

Attracted, decrease

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

Bond energy

A structural formula in which electrons are represented by dots; dot pairs or dashes between two atomic symbols represent pairs in covalent bonds

Lewis structures

The pair of dots representing a shared pair of electrons in a covalent bond is often replaced by a ____ _____.

Long dash

A neutral group of atoms help together by a covalent bonds is a

Molecule

Many chemical compounds, including most of the chemicals that are in living things and are produced by living things, are composed of _____.

Molecules

Other elements can be surrounded by____ than eight electrons when they combine with the highly electronegative elements fluorine, oxygen, and chlorine

More

A bond in which the atoms share ore than one pair of electrons such as a double bond or a triple bond

Multiple bond

Covalent bonds form from ____ ____.

Shared electrons

How is resonance indicated?

To indicate resonance, a double-headed arrow is placed between a molecule's resonance structures.

A triple covalent bond, or simply a_____ _____, is a covalent bond in which three pairs of electrons are shared between two atoms

Triple bond

T or F Bond lengths and energy vary from molecule to molecule.

True

T or F Electron-dot notation can also be used to represent molecules

True

T or F Electron-dot notations can represent compounds.

True

Picture two isolated hydrogen atoms separated by a distance large enough to prevent them from influencing each other. At this distance, the overall potential energy of the atoms is arbitrarily set at _____, as shown in part (a) of Figure 6.2.2.

Zero

Bond length is the average distance between two bonded atoms

at which potential energy is at a minimum

Thus, the atoms are drawn to each other and their potential energy is_____, as shown in part (b) of Figure 6.2.2

lowered

A ____ is a neutral group of atoms that are held together by _____ bonds.

molecule, covalent

What group of elements satisfies the octet rule without forming compounds

noble gases (group 18)

Unlike other atoms, the___ ___ atoms exist independently in nature.

noble-gas

Chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in its highest occupied energy level.

octet rule

Most main-group elements tend to form covalent bonds according to the____ ____.

octet rule

Atoms tend to form bonds to follow the____ ____.

octet rule.

Covalent bond formation usually involves only the electrons in an atom's _____ energy levels, or the atom's valence electrons

outermost

Each atom has a nucleus containing a single positively charged____.

proton

The nucleus of each atom is surrounded by a negatively charged electron in a ____ _____ orbital

spherical 1s

When the atoms first "sense" each other, the electron-proton attraction is_____ than the electron-electron and proton-proton repulsions

stronger

A formula that indicates the location of the atoms, groups, or ions relative to one another in a molecule and that indicates the number and location of chemical bonds

structural formula

A combination of chemical symbols and numbers to represent a substance

Chemical formula

The composition of a compound is given by its _____ _____.

Chemical formula

An ____ ____ , also called a____ ____ , is a pair of electrons that is not involved in bonding and that belongs exclusively to one atom.

Unshared pair, lone pair

In these cases of____ _____, bonding involves electrons in d orbitals as well as in s and p orbitals

expanded valence

_____ _____ is the energy required to break a chemical bond and form neutral isolated atoms

Bond energy

The distance between two bonded atoms at their minimum potential energy, that is, the average distance between two bonded atoms, is the____ _____

Bond length

A ____ _____ contains only two atoms

Diatomic molecule

The relative strength of attraction and repulsion between the charged particles depends on the_____ separating the atoms

Distance

____ placed around an element's symbol can represent valence electrons

Dots

An electron-configuration in which only the valence electrons of an atom of a particular element are shown, indicated by dots placed around the element's symbol

Electron- dot notation

These representations are all ____ ____, formulas in which atomic symbols represent nuclei and inner-shell electrons, dot-pairs or dashes between two atomic symbols represent electron pairs in covalent bonds, and dots adjacent to only one atomic symbol represent unshared electrons

Lewis structures

The bonded atoms vibrate a bit, but as long as their potential energy remains close to the_____, they are covalently bonded to each other

Minimum

At this point, the electrons of each hydrogen atom of the hydrogen molecule are shared between the _____

Nuclei

In forming a covalent bond, the hydrogen atoms ______ _____ as they change from isolated individual atoms to parts of a molecule.

Release energy

At the same time, the two nuclei ____ each other and the two electrons____ each other, which results in an____ in potential energy.

Repel, repel, increase

The bonding in molecules or ions that cannot be correctly represented by a single Lewis structure

Resonance

The same amount of energy must be added to____ the bonded atoms

Separate

A covalent bond in which two atoms share one pair of electrons

Single bond

What does the amount of energy released equal?

The amount of energy released equals the difference between the potential energy at the zero level (separated atoms) and that at the bottom of the valley (bonded atoms) in Figure 6.2.2

T or F The need for a multiple bond becomes obvious if there are not enough valence electrons to complete octets by adding unshared pairs

True

T or F They possess a minimum of energy existing on their own because of the special stability of their electron configurations.

True

_____ _____ are even stronger and shorter. Figure 6.2.10 compares average bond lengths and bond energies for some single, double, and triple bonds.

Triple bonds

T or F A single molecule of a chemical compound is an individual unit capable of existing on its own. It may consist of two or more atoms of the same element, as in oxygen, or two or more different atoms, as in water or sugar

True

T or F As shown in Figure 6.2.4, the molecule's electrons can be pictured as occupying overlapping orbitals, moving about freely in either orbital.

True

T or F As the atoms near each other, their charged particles begin to interact.

True

T or F However, bond lengths and bond energies vary with the types of atoms that have combined

True

T or F In Figure 6.2.2, the bottom of the valley in the curve represents the balance between attraction and repulsion in a stable covalent bond

True

T or F In general, an element's number of valence electrons can be determined by adding the superscripts of the element's noble-gas notation

True

T or F In the case of covalent bond formation, this idea is illustrated by a simple example, the formation of a hydrogen-hydrogen bond.

True

T or F In writing Lewis structures for molecules that contain carbon, nitrogen, or oxygen, one must remember that multiple bonds between pairs of these atoms are possible

True

T or F Resonance structures show hybrid bonds

True

T or F Some atoms can share multiple pairs of electrons

True

T or F Some compounds are networks of bonded atoms

True

T or F Some molecules and ions cannot be represented adequately by a single Lewis structure

True

T or F The attractive force continues to dominate and the total potential energy continues to decrease until, eventually, a distance is reached at which the repulsion between the like charges equals the attraction of the opposite charges

True

nature favors ____ ____ because most atoms have lower potential energy when they are bonded to other atoms than they have when they are independent particles

chemical bonding

A ____ ____ indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts

chemical formula

The _____ _____ of a molecular compound is referred to as a molecular formula

chemical formula

When two hydrogen atoms form a molecule, they share electrons in a_____ ______.

covalent bond

A single water molecule consists of one oxygen atom joined by separate ____ _____ to two hydrogen atoms.

covalent bonds

A molecule of oxygen, O2, is an example of a _____ molecule.

diatomic

A double covalent bond, or simply a ______ ______, is a covalent bond in which two pairs of electrons are shared between two atoms

double bond

How is a double bond shown?

double bond is shown either by two side-by-side pairs of dots or by two parallel dashes.

_____ ______ in general have greater bond energies and are shorter than single bonds.

double bonds

Scientists usually report bond energies in ___ ____ ___, which indicates the energy required to break one mole of bonds in isolated molecules.

kilojoules per mole (kJ/mol)

In drawing a Lewis structure, the central atom is generally the

least electronegative atom

a chemical compound whose simplest units are molecules

molecular compound

A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms

molecular formula

A_____ _____ shows the types and numbers of atoms combined in a single molecule of a molecular compound. The molecular formula for water, for example, is H2O

molecular formula

Which of the following shows the types and numbers of atoms joined in a single molecule of a molecular compound?

molecular formula

the smallest unit of a substance that keeps all of the physical and chemical properties of that substance; it can consist of one atom or two or more atoms bonded together

molecule

the triple bond in nitrogen is ___ ___

nonpolar covalent

A single covalent bond, or a____ _____, is a covalent bond in which one pair of electrons is shared between two atoms.

single bond

A____ ____ indicates the kind, number, arrangement, and bonds but not the unshared pairs of the atoms in a molecule

structural formula