Chemistry Unit 3: Bonding Vocab

Atom

The smallest unit of matter

Element

A specific atom

Molecule

Two or more elements bonded together (can be the same or different)

Compound

Two or more DIFFERENT elements bonded together

Pure Substance

All molecules/atoms are the same within a sample

Mixture

Molecules/atoms are different within a sample

Covalent solids have very ______ (strong/weak) intramolecular covalent bonds & ______ (strong/weak) intermolecular forces

Strong, Weak

Intramolecular Bonds

Bonds between atoms within a molecule

Intermolecular Forces

Forces/attraction that exist between molecules

Ionic Bond

Complete transfer of valence electrons(s) between atoms. Generates two oppositely charged ions. Has an electronegativity difference greater than 1.7.

Covalent Bond

Sharing electrons to reach the octet rule and become more stable. Formed between atoms with similar electronegativities and has an electronegativity difference of less than 1.7.

Nonpolar Covalent Bond

Difference in electronegativity between bonded atoms is less than 0.5 (very similar electronegativities)

Polar Covalent Bond

Difference in electronegativity between bonded atoms is between 0.5 and 1.9 (slightly different electronegatvities)

The types of intermolecular forces (in order from strongest → weakest) are:

Hydrogen Bonding, Dipole-Dipole, & Induced Dipole

Hydrogen Bonding

Occurs when a H atom is bonded to either an O, N, or F atom. δ⁺ end of hydrogen is attracted to the δ^- end of the O, N, or F of another molecule. This is the strongest force of intermolecular attraction, making it have high BPs and MPs.

Dipole-Dipole

Forces occur when the δ⁺ charged part (pole) of a molecule interacts with the δ^- charged part (pole). Out of the intermolecular forces, this is in the middle regarding strength.

Induced Dipole

Forces between essentially non-polar molecules. “Temporary dipoles” are formed by the shifting of the electron clouds within molecules. These temporary dipoles attract or repel the electron clouds of nearby non-polar molecules. This is the weakest kind of attraction.

Order of the type of bonds from weakest → strongest attraction

Induced Dipole, Dipole-Dipole, Hydrogen Bonding, Ionic Bonds

Ionic Compounds Properties

Crystalline solid at room temperature, high melting points, conducts electricity as a liquid, soluble in water, conducts electricity when dissolved in water.

Covalent Compounds Properties

Liquid, gas, & solid at room temperature, low melting points, doesn’t conduct electricity, not soluable in water

Odd-Electron Molecules

A violation of the octet rule

Some stable compounds have an odd number of electrons in their valence shells

Electron-Deficient Molecules

A violation of the octet rule

Occurs when stable compounds have less than eight electrons around the central atom

Expanded Valence Shells Molecules

A violation of the octet rule

Occurs when more than 8 electrons are assigned to the valence shell. Formed only by central atoms in the third row of the periodic table or beyond because they have empty d orbitals in their valence shells.

Formal Charge

A way to determine which structure is the most valid and would exist in real life. Molecules are the most stable when the formal charge is minimized.

Formal Charge Formula

The # of valence electrons it should have (period number) - actual amount of valence electrons it has

OR

Valence electrons - nonbinding valence electrons - # of bonds

Electronegative elements are more likely to gain a ______ charge.

Negative