Unit 6, 7 and 8

Symbol

A one, two, or three letter designation for an element (Ex. Sodium is Na)

Subscript

A number written to the right and below a symbol that tells the number of atoms present in a molecule (Ex. An oxygen molecule has two oxygen atoms, O2)

Formula

Symbols and subscripts used to represent the composition of a substance (can be ionic or covalent (Ex. H2O, KCl)

Chemical Bonds

Forces that hold atoms together, protons of one atom and electrons of another are attracted

Ionic bonds

Bonds between metals and nonmetals where electrons are transferred, forming ions

Compound

A substance composed of 2 or more elements chemically combined in definite proportions

Polyatomic Ion

A group of covalently bonded atoms possessing a charge, participating in ionic bonding (Ex. NH4+, CO3-2)

Lewis Dot Diagram

Placing valence electrons around an element's symbol to represent bonding

Covalent bonds

Bonds between nonmetals where valence electrons are shared to achieve octets

Polarity

Measure of electron distribution within a molecule, determined by electronegativity differences

VSEPR (Valence Shell Electron Pair Repulsion)

Molecular shape depends on the pairs of valence electrons around the central atom which repel each other

Physical Change

Change in state or appearance without altering the substance's identity

Chemical Change

Change where the identity of products differs from the reactants, indicating a chemical reaction

Reactant

Substance entering a reaction, found on the left side of the equation

Product

Substance formed in a reaction, located on the right side of the equation

Coefficient

Number written in front of a formula indicating the quantity of substances or molecules in a reaction

Nonpolar

Even distribution of electrons, same electronegativity (same element), share electrons equally (Ex. H2, O2)

Polar

Uneven distribution of electrons, different electronegativities (different elements), do not share electrons equally

SNAP

Symmetrical Polar, Asymmetrical Nonpolar

Linear Shape

2 atoms bonded to central atom, one lone pair on central atom, 2 repulsive units, 180 degree bond angle.

Trigonal Planar Shape

3 atoms bonded to central atom, 0 lone pairs on central atom, 3 repulsive units, 120 degree bond angle.

Bent or V-Shaped Shape

2 atoms bonded to central atom, 2 lone pairs on central atom, 4 repulsive units, 105 degree bond angle.

Trigonal Pyramid Shape

3 atoms bonded to central atom, 1 lone pairs on central atom, 4 repulsive units, 107 degree bond angle.

Tetrahedral

4 atoms bonded to central atom, 0 lone pairs on central atom, 4 repulsive units, 109.5 degree bond angle.

Synthesis Reaction

A chemical reaction where two or more substances combine to form a single, more complex product. A+B —> AB

Decomposition Reaction

A type of chemical reaction where a single compound breaks down into two or more simpler substances. AB —> A+B

Single Replacement Reaction

A type of chemical reaction where an element replaces another element in a compound, resulting in a new compound and a different element. A + BC —> B + AC

Double Replacement Reaction

Two compounds swapping ions to form two new compounds. It typically occurs in aqueous solutions and can produce a precipitate, gas, or water. AB + CD → AD + CB

Combustion Reaction

A substance combines with oxygen gas to produce heat, light, and new chemical compounds. C_xH_y + O₂ → H₂O + CO₂

Law of Conservation of Mass

States that matter AND energy are both conserved in a chemical reaction (charge is also conserved).