PAGE 3 — Chemical Bonds & PAGE 4 — Electronegativity & Polarity

What is an ionic bond?

A bond formed when electrons are transferred from one atom to another.

Which types of elements form ionic bonds?

A metal and a nonmetal

• electron transfer between metal + nonmetal

How does a metal behave in ionic bonding?

It loses electrons and becomes a cation.

How does a nonmetal behave in ionic bonding?

It gains electrons and becomes an anion.

Why do ionic bonds form?

Because opposite charges attract (cation + anion).

What particle moves during ionic bonding?

Electrons (never protons or neutrons).

What holds ionic compounds together?

Electrostatic attraction between positive and negative ions.

Are ionic bonds strong or weak?

Strong due to charge attraction.

What is the structure of ionic compounds?

A crystal lattice of alternating positive and negative ions.

Do ionic compounds conduct electricity?

Yes, but only when molten or dissolved (ions can move).

What are the forces holding ions together?

Electrostatic attraction

What is a repeating ionic structure?

Crystal Lattice

When ionic compounds conduct when ions can move it is called?

Conductivity

What is a covalent bond?

A bond formed when atoms share electrons.

Which types of elements form covalent bonds?

Two nonmetals.

Why do atoms form covalent bonds?

To fill their valence shells and become stable.

What particle is shared in covalent bonding?

Electrons, specifically valence electrons.

What is a single covalent bond?

One pair of shared electrons.

What is a double covalent bond?

Two pairs of shared electrons.

What is a triple covalent bond?

Three pairs of shared electrons.

Are covalent bonds strong or weak?

Strong bonds within molecules.

Do covalent compounds conduct electricity?

No, because they do not form ions.

What are a group of atoms held together by covalent bonds?

Molecule

What are the specific electrons involved with bonding?

Valence Electrons

What is a polar covalent bond?

A covalent bond with unequal sharing of electrons due to a difference in electronegativity.

What is a nonpolar covalent bond?

A covalent bond with equal sharing of electrons.

What causes a bond to be polar?

One atom has a higher electronegativity and pulls electrons closer.

What causes a bond to be nonpolar?

Atoms have similar or identical electronegativity.

What is a dipole?

A molecule with partial positive and partial negative ends (only in polar bonds).

Example of a polar bond?

H–O (oxygen pulls electrons more strongly).

Example of a nonpolar bond?

H–H or Cl–Cl (same atoms → equal sharing).

Do polar molecules mix with water?

Yes

• water is polar (“like dissolves like”).

Do nonpolar molecules mix with water?

No

• they are hydrophobic.

What determines bond type?

Electronegativity difference

What is a polar molecule?

A molecule with partial positive and partial negative ends (a dipole).

What molecule has an even charge in distribution?

Nonpolar Molecule

What is a hydrogen bond?

A weak attraction between a hydrogen atom and a nearby electronegative atom (like O, N, or F).

Are hydrogen bonds stronger or weaker than covalent bonds?

Weaker than covalent bonds.

Are hydrogen bonds stronger or weaker than typical intermolecular forces?

Stronger than most other intermolecular forces.

What causes hydrogen bonds to form?

A polar molecule where hydrogen is bonded to a highly electronegative atom.

What atoms commonly participate in hydrogen bonding?

Oxygen (O), nitrogen (N), fluorine (F).

Why is water’s boiling point high for its size?

Because hydrogen bonds require extra energy to break.

What gives water its unique properties (cohesion, adhesion, surface tension)?

Hydrogen bonding between water molecules.

Are hydrogen bonds within a molecule or between molecules?

Between molecules (intermolecular).

What are the force between molecules; hydrogen bonds are one type?

Intermolecular force

What is water sticking to water via hydrogen bonds?

Cohesion

What is water sticking to other surfaces via hydrogen bonds?

Adhesion

What is electronegativity?

An atom’s ability to attract electrons in a chemical bond.

Which element has the highest electronegativity?

Fluorine (F)

What happens when the electronegativity difference is large?

An ionic bond forms.

What happens when the electronegativity difference is small?

A polar covalent bond forms.

What happens when electronegativity is equal or almost equal?

A nonpolar covalent bond forms.

What is the trend across a period (left → right)?

Electronegativity increases.

What is the trend down a group (top → bottom)?

Electronegativity decreases.

Why does electronegativity increase across a period?

More protons pull electrons more strongly.

Why does electronegativity decrease down a group?

More electron shells reduce attraction.

What is polarity?

An uneven distribution of electrons in a molecule, creating partial charges.

What causes a molecule to be polar?

Unequal sharing of electrons due to electronegativity differences.

What is a nonpolar molecule?

A molecule with even electron distribution and no dipole.

What two things determine if a molecule is polar?

• Electronegativity difference

• Molecular shape (symmetry)

What measures how strongly atoms pull or attract electrons to themselves to form chemical bonds?

Electronegativity

Atoms with similar electronegativity are most likely to bond?

Covalently

What is the most basic type of matter?

An element

• has unique properties and cannot be broken down

  into other elements

The smallest unit in an element is an?

Atom

A chemical combination of two or more types of elements is called a?

Compound

Metals lose electrons because?

They have fewer electrons in their outer shell

• resulting in them forming cations

Non-metals gain electrons because?

They have more electrons in their outer shell

• resulting in them forming anions

What are typically the most electronegative?

Nonmetals

What are typically the least electronegative?

Metals

All diatomic molecules have?

Covalent bonds between the same atoms

When the difference in electronegativity between the two atoms is greater or equal to 0.5, it is called a?

Polar covalent bond

When the difference in electronegativity between the two atoms is less or equal to 0.5, it is called a?

Non polar covalent bond

• all diatomic molecules