Q3 Review "Chemical Bonding"

This kind of chemical bond involves the sharing of valence electrons

• ionic

• covalent

• metallic

• nirvanic

Answer explanation

co - means "together" or "shared"

valent - refers to the valence shell.

covalent = sharing valence e- (where neither atom has a charge) Takes place between nonmetals to other nonmetals like C-C , C-H, or S-O. leads to formation of molecules in most cases)

ionic bonds are attractions between oppositely-charged particles. Such as between Na⁺ and Cl^-, or between Na⁺ and SO₄^2-

metallic bonding is between metal atom to metal atom. (think sea of mobile electrons that allows free flow... hence conducts current easily)

To form an ionic bond, electron(s) _____

• are transferred

• are shared

• enter into a mobile sea

• do not do anything

Answer explanation

neutral atoms become ions when an electron is transferred. (Typically from metal to the nonmetal)

Afterward, they are charged particles that attract each other into an ionic bond.

What type of bonding takes place in MgBr₂ ?

• metallic

• ionic

• covalent

• both ionic and covalent

Answer explanation

magnesium bromide, MgBr is composed of a metallic element (magnesium) and a nonmetallic element (bromine).

A metal + nonmetal combination is ionic bonding.

(The metal is a positive ion and the nonmetal is a negative ion... opposites attract)

What type of bonding takes place in pure iron, Fe?

• metallic

• ionic

• covalent

• both ionic and covalent

Answer explanation

Whenever a substance is composed of only metal atoms, the bonding is metallic. (as the name would suggest)

What type of bonding takes place in sulfur dioxide, SO₂ ?

• metallic

• ionic

• covalent

• both ionic and covalent

Answer explanation

sulfur dioxide is composed of only nonmetallic elements.

(S = sulfur and O = oxygen both are found to the right of the staircase line)

nonmetal + nonmetal involves covalent bonding.

(Note: covalent bonding is the sharing of electrons because both elements attract outer electrons too well for a complete transfer to take place)

What type of bonding takes place in MgSO₄ ?

• metallic

• ionic

• covalent

• both ionic and covalent

Answer explanation

When there are more than 2 elements in a formula, you should suspect that a portion of the formula is a polyatomic ion. (especially if the formula has "O₃" or "O₄" as part of it)

Turns out that the SO₄ portion of MgSO₄ is sulfate, a polyatomic ion with charge of 2-. ( SO₄^2- )

You can find it listed in Reference Table E.

The oxygens are bonded covalently to the sulfur, but there are 2 more electrons than protons overall for those 5 atoms... making that set an ion (hence, the 2- charge)

Then, it bonds ionically with the metal cation.

Both types of bonds, covalent and ionic, exist in the substance.

The Lewis structure of CH₄, would display which type of covalent bonds?

• single covalent bonds only

• double covalent bonds only

• a mix of single and double covalent bonds

Answer explanation

CH₄ can be called carbon tetrahydride, but is also known as methane.

The carbon is the central atom of the molecule and has 4 hydrogens covalently bonded to it.

Each bond contains a single pair of electrons, meaning each is a single covalent bond. See the gif for how the structure is created from the Lewis Dot diagrams of the individual atoms.

When a chemical bond forms, energy is ___________.

• absorbed

• released

• destroyed

• created

Answer explanation

It probably makes sense that to break a bond, energy must be absorbed. (bonds are attractions and attractions do not tend to break themselves.)

But the question is about forming a bond, not breaking one...

Since forming a bond is opposite of breaking a bond, the energy must be opposite (it releases energy instead of absorbing it).

This may seem like energy is created, but keep in mind that energy cannot be created nor destroyed. It can only be transferred or change form. (Conservation of Energy).

Covalent network solids...

• involve atoms bonded into molecules

• involve atoms bonded into vast structures

• involve a sea of mobile electrons

Answer explanation

examples of covalent network solids include diamond and glass.

Atoms are all connected and form a HUGE crystalline structure

This is very different than molecules which are small, individual particles. (such as water molecules or oxygen gas molecules.)

oxygen gas (O₂) and ozone (O₃) are examples of

• isotopes

• covalent network solids

• alloys

• allotropes

Answer explanation

When two substances are both made of the same element , but have different arrangement of atoms (i.e. different molecular structures)... they are called allotropes.

Another common allotrope set is graphite and diamond, both pure forms of carbon.