Chemistry Test Vocabulary

Electron Domain

• Any area of electron density around a central atom

• Ex.

  • A single, double, or triple covalent bond is one electron domain

  • A nonbonding pair of electrons is one electron domain

Covalent compounds

Chemical bond between

• Two nonmetals

• metalloids and a nonmetal

• NEVER a metal

• Often called molecular compounds or molecules

• Electrons are SHARED, not transferred

VSEPR

• This explains why molecules have different shapes

  • Valence

  • Shell

  • Electron

  • Pair

  • Repulsion

• Electron domains all have negative charge so all the domains repel each other around the central atom

Binary Compound

• A chemical substance composed of exactly two different elements

• The number of atoms of each element doesn’t matter, as long as there are only two distinct types of elements in the chemical formula, it is classified as a binary compound

• Ex. NaCl, MgO, CaCl2, H2O, CO2

Electron Dot Diagram

• A diagram that represents only the valence electrons of an atom of an element

• The nucleus and all inner electrons are represented by the element symbol

• Valence electrons are added one at a time to each side around the symbol, pairing up after four are added

Partial Charge

Dipole-dipole force

• Attraction between molecules that have a permanent dipole caused by polar bonds in a polar molecule

Electronegativity

• An atom’s ability to attract shared electrons towards itself in a chemical bond

Polar covalent bond

• A covalent bond in which the difference in electronegativity IS LARGE so that the electrons are pulled toward the more electronegative atom

• Results in a positive end of the bond and a negative end to the bond (dipole)

• FONCl

Nonpolar covalent bond

• A covalent bond in which the difference in electronegativity difference IS SMALL so that neither atom pulls more strongly on electrons and the electrons are evenly distributed across the bond

Cation

• A positively charged ion

• Forms when an atom or molecule loses one or more negatively charged electrons, resulting in more protons than electrons

Anion

• An atom or molecule with a net negative electrical charge

• Forms when an atom gains one or more electrons, meaning it has more electrons than protons

Dispersion force

• Attraction between atoms or molecules caused by temporary dipole as electrons move (in all molecules/substances)

• Increase with atomic mass and surface area of molecule

Dipole

• A separation of opposite electrical or magnetic charges

• Basically means an object or system has two poles: a positive end and a negative end (north and south pole)

Molecular geometry

• A description of the arrangement of the atoms bonded to the central atom

• The description gives you an idea of the shape of the molecule only with respect to bonded atoms even though this shape is affected by the nonbonding pairs of electrons on the central atom as well

Electron domain geometry

• A description of the arrangement of all the electron domains around a central atom

• The description gives you an idea of the arrangement of the electron domains around the central atom

Electron Geometry = Molecular Geometry when…

• The number of total domains around a central atom is the same as the number of bonded domains around the central atom

Covalent bond

Hydrogen bonding

• Forces of attraction that occur between a hydrogen atom in a polar bond of H-F, H-O, or H-N and a nonbonding pair of electrons on a nearby N, O, or F atom

  • Very strong attractions

  • Contributes to many of water’s unique properties

Ionic bond

• A chemical bond formed through the electrostatic attraction between oppositely charged ions

• A metal and a nonmetal

molecule

• The smallest fundamental unit of a chemical compound that can take part in a chemical reaction

• Ex.

  • H2O

  • O2

  • CO2

valence electrons

• Electrons that make up the outer electron shell of an atom

intermolecular forces

• Forces of attraction BETWEEN molecules or atoms

• Much weaker than bonds which are forces of attraction WITHIN a molecule connecting two atoms

  • Energy needed to boil HCl = 16 kl/mol

  • Energy needed to break the H-Cl bond = 431 kl/mol

• All intermolecular forces are electrostatic meaning they originate from attractions between opposite charges