Physical Science - Chapter 5

What is a chemical bond?

What is a chemical bond?

an electrostatic attraction that exists between atoms resulting from the sharing or exchanging of valence electrons.

(True or False) Compounds often have physical and chemical properties that are similar to those of the elements of which they are made.

False. Typically compounds have significantly different properties than the elements that they contain.

Must atoms of one element always bond with atoms of a different element in order to become stable? Explain.

No. Atoms of the same element can sometimes become stable by bonding with each other, such as in diatomic molecules of oxygen or nitrogen.

Describe an example of an element that does not need to meet the octet rule requirement in order to become stable.

Hydrogen can become stable by either gaining one electron or losing its one valence electron. Helium already has a full first energy level. Lithium, beryllium, and boron can all become stable by losing the electrons in their second (valence) energy level.

What is a covalent bond?

the attraction between two atoms due to the sharing of valence electrons.

Define the term multiple bond.

Multiple (double or triple) bonds exist when a pair of atoms share more than one pair of electrons.

(True or False) A triple bond holds three atoms together.

False. A triple bond is the sharing of three pairs of electrons by two atoms.

What is a polar covalent bond?

A bond that forms between two atoms with moderately differing electronegativities. The valence electrons between the atoms are shared but the sharing is unequal. The electrons are held closer to the atom with the higher electronegativity.

Knowing that the electronegativity of oxygen and sulfur are 3.4 and 2.6 respectively, do you think that sulfur dioxide contains polar or nonpolar bonds? Explain.

Oxygen is more electronegative than sulfur and will exert a greater pull on the shared electrons, so all of the bonds shown will be polar.

Actual sulfur dioxide molecules are bent, just as the Lewis structure shows. Are molecules of sulfur dioxide polar or nonpolar? Explain.

Sulfur dioxide is polar since the oxygen atoms will pull shared electrons toward their side of the molecule, resulting in that side having a negative charge. The sulfur side of the molecule will be positive.

If two sulfur atoms bond with each other, will they form a single bond or a double bond? Explain.

Each sulfur atom needs two additional valence electrons to satisfy the octet rule, so they will share two pairs of electrons and form a double bond.

Will a sulfur molecule that’s bonded with another sulfur molecule be polar or nonpolar? Explain.

Since the electronegativity of the two atoms is the same, they will share electrons equally, producing a nonpolar molecule.

What is used to represent the ratio of ions in a group of ionically bonded atoms?

a formula unit

Describe a metallic bond.

It occurs between metals. Because metals have low electronegativities, they easily release their valence electrons. The metal atoms form a lattice structure and share all of their valence electrons.

If two atoms have very different electronegativities, will they form an ionic bond or a covalent bond?

ionic

Identify if the following elements would be more likely to gain or lose electrons in order to form an ionic bond.

a. bromine

gain

Identify whether each of the following elements would be more likely to gain or lose electrons in order to form an ionic bond:

rubidium & strontium

lose

Will two iodine atoms form an ionic or covalent bond? Explain.

The electronegativity of two iodine atoms is the same, therefore the two atoms must share electrons in a covalent bond.

In a compound of strontium and fluorine, which element forms an anion? Which forms a cation?

Fluorine forms an anion; strontium forms a cation.

What does a chemical formula tell about a compound?

It tells the identity and number of atoms of each element in the compound.

a. sodium and bromine

sodium bromide, NaBr

b. calcium and chlorine

calcium chloride, CaCl2

c. barium and nitrate barium

nitrate, Ba(NO3)2

Predict the name and formula for compounds containing the following elements or polyatomic ions.

d. nickel and fluorine

nickel (II) fluoride, NiF2

What does an oxidation state indicate about an element?

It indicates the electric charge gained or lost by that element when it forms a compound

Which of the following compounds are salts? Explain.

a. selenium dioxide

b. barium iodide

c. sulfur dibromide

d. triphosphorus pentanitride

b.; Salts are formed when a metal and nonmetal form an ionic compound. Only barium iodide is an ionic compound.

Name the elements and the number of atoms of each element in the chemical formula C5H11NO3.

five atoms of carbon, eleven atoms of hydrogen, one atom of nitrogen, and three atoms of oxygen

Which is (are) the primary oxidation state(s) for each of the following elements?

a. scandium

+3

Which is (are) the primary oxidation state(s) for each of the following elements?

b. sulfur

+6, +4, +2, −2

Which is (are) the primary oxidation state(s) for each of the following elements?

c. zirconium

+4

Which is (are) the primary oxidation state(s) for each of the following elements?

d. iodine

+7, +5, +3, +1, −1

Using primary oxidation states (see table on page 113), predict the names and formulas for two different compounds composed of nitrogen and oxygen.

Are the compounds nitrogen and oxygen, using primary oxidation states, that form dinitrogen trioxide (N2O3) and dinitrogen pentoxide (N2O5), the only possible compounds of nitrogen and oxygen? Explain.

No. Since these compounds were predicted from only the primary oxidation states, there could be other compounds that are based on the other oxidation states.