Physical Science Chapter 5.B Test Prep

Define: Covalent Bond

A chemical bond formed as a result of two atoms sharing valence electrons.

Define: Ionic Bond

A chemical bond formed when atoms transfer valence electrons.

Define: Lewis Structure

A system for modeling the covalent bonds between atoms in a molecule and any unbonded electrons in the molecule. A.K.A. A representation of the atoms in a covalent bond and the electrons being exchanged.

How many of the bonds shown in the Lewis structure for chloromethane are polar? Explain.

All of the bonds are polar because each bond is between two atoms with different electronegativities.

How can you tell how many valence electrons a element has?

An elements group number will say how many valence electrons the elements in that group has. For example an element in group 5 would have 5 valence electrons.

How do electronegativities affect atoms electrons?

Atoms with high electronegativities hold on to their valence electrons tighter and are eager to acquire more, while atoms with lower electronegativities will pull on their electrons loosely and easily give their electrons up.

What are Lewis Structures?

Diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule.

Do ionic bonds tend to form between atoms with similar or dissimilar electronegativities?

Dissimilar

What are these diatomic molecule elements?

Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, and Iodine. They are also known as the Hydrogen Seven, as all the elements, except Hydrogen, form a 7 shape in the periodic table of elements.

What are covalent bonds and how do electronegativities affect covalent bonding between atoms?

If two atoms have similar electronegativities neither will give their electrons up. In this case they share their electrons with each other to become stable. The chemical bond that is made from this is called a covalent bond. Covalent bonds most often form between nonmetals.

Describe the role of electrons in covalent, ionic, and metallic bonds.

In covalent bonding, electrons are shared between atoms. In ionic bonding , one atom loses electrons while the other gains them. In metallic bonding, there is a "sea" of freely moving electrons being shared by all the metal atoms in a lattice.

What do the red electrons shown in Lewis Structures represent?

In the case of two oxygen atoms being bonded, the red electrons represent the double bond that is taking place between the two oxygen atoms.

What are ionic bonds and how do electronegativities affect ionic bonding between atoms?

Ionic bonds are formed between an atom with high electronegativities and an atom with low electronegativities. The atom with low electronegativities will give up electrons to the one with higher electronegativities. this results in the lower atom becoming a cation (a positively charged ion), while the higher atom becomes an anion (a negatively charged ion). Ionic substances, unlike covalent bonds, form crystals rather than molecules.

Who made the Lewis Structure? When was it made?

It was made in 1916 by the chemist, Gilbert Lewis.

What are polyatomic molecules?

Molecules consisting of many atoms.

Why do atoms bond?

Most atoms are seeking to have eight valence electrons to become stable (see Octet Rule).

What are polar molecules?

Polar molecules are molecules that have areas of slightly positive and negative charge. This results in them being 'sticky' and being able to form larger structures with other polar molecules.

What do we call the unequal distribution of electric charge?

Polarity.

How many elements are found as diatomic molecules in nature?

Seven

Define: Metallic Bond

The attraction between metal atoms and their collectively shared valence electrons.

What is a formula unit?

The formula unit is the smallest unit of any ionic compound.

Define: Formula Unit

The smallest whole-number ratio of ions within an ionic compounds.

If the atoms in an ionic bond are not sharing electrons, what keeps the atoms together?

They are held together by the opposite electric charges on the ions that are formed.

How do atoms bond?

They either gain, lose, or share electrons in order to bond and achieve the Octet Rule.

Under what circumstances will a triple bond form?

Triple bonds form when atoms must share three pairs of electrons to satisfy the octet rule.

What is a single covalent bond?

A covalent bond where the atoms only share one atom.

Define: Diatomic Molecule

A molecule made of two atoms.

What is a nonpolar bond?

A nonpolar bond is when electrons are shared equally between two or more atoms because they have equal pull against each other

What is a polar covalent bond?

A polar covalent bond is when an atom is taking electrons more than the other atoms just sharing electrons. The other atoms electronegativities are too low to resist the pull towards the atom with higher electronegativity, resulting in the higher atom getting the electrons it wants.

What are double covalent bonds?

Chemical bonds where two electrons are being shared. They are stronger than single covalent bonds.

What happens when Sodium and Chlorine bond?

Chlorine (with high electronegativity) takes sodium's (having low electronegativity) one valence electron to complete its third energy level. Sodium now has no electrons in its third energy level, but has a full set in its second energy level so it is also complete.

What are metallic bonds and how do electronegativities affect metallic bonding between atoms?

Metallic bonds are between atoms that have low electronegativities. Since these atoms hold onto their electrons very loosely the metallic bond becomes a structure of many atoms, all exchanging electrons freely. A metallic bond is the attraction between metal atoms and their sea of shared electrons.

How are do ionic bonds form crystals?

The reason Ionic bonds form crystals is because of their nature. The cation (+) and anion (-) that were previously discussed connect to cations and anions from other ionic bonds to create a 'chain' of ions within a lattice structure, as opposites attract.

Define: Polarity

The unequal distribution of electric charge in a covalent bond.

Is chloromethane a polar molecule? Defend your answer.

Yes. The polarity of the C-CI bond is different from that of the C-H bonds, causing an unequal distribution of charge on the molecule.