CHEM Chapter 2

Element

Contains only one type of atom

Molecule

Contains two or more atoms that are covalently bonded

Compound

Two or more different elements that are chemically combined in a specific ratio by mass, cannot be physically separated

Pure Substance

Contains only one substance

Mixture

Contains two or more pure substances, can be physically separated

Heterogenous Mixture

Contains two or more distinct phases

Homogenous Mixture

Contains a single phase

Phase

A region containing one substance that has physical boundaries

Law of Mass Conservation

Mass before reaction is the same as mass after reaction

X Symbol

Chemical symbol for the substance

Z Symbol

Atomic number, represents number of PROTONS in the nucleus, determines the element

A Symbol

Mass number, represents number of protons AND neutrons, defines the mass of one atom of the element

Ion

An atom with a charge

Cation

Positive ion

Anion

Negative ion

Isotope

Atoms/ions of an element that have a different number of neutrons

Unstable

Undergoing nuclear decay

Periods

Rows of the periodic table

Groups

The columns of the periodic table

Group A

Main Group Elements

Group B

Transition Elements/Metals

Elements 58-71 and 90-103

Rare-Earth Metals (Inner Transition Elements/Metals)

Group 1A

Alkali Metals

Group 2A

Alkaline Earth Metals

Group 7A

Halogens

Group 8A

Noble Gases

Elements to the Left of the “Staircase” Line

Metals

Elements to the Right of the “Staircase” Line

Nonmetals

Elements in the “Staircase” Line

Metalloids

Diatomic Elements

Br, I, N, Cl, H, O, F

Polyatomic Ions

Ammonium, Hydroxide, Chlorate, Nitrate, Carbonate, Sulfate, Phosphate

NH₄¹⁺

Ammonium’s chemical formula

OH^1-

Hydroxide’s chemical formula

ClO₃^1-

Chlorate’s chemical formula

NO₃^1-

Nitrate’s chemical formula

CO₃^2-

Carbonate’s chemical formula

SO₄^2-

Sulfate’s chemical formula

PO₄^3-

Phosphate’s chemical formula

Law of Definite (or Constant) Composition

No matter what the source of a compound, it’s elements occur in the same proportion by mass

Law of Multiple Proportions

If elements A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers

How is Atomic Mass calculated/found?

By taking each naturally occurring isotope and calculating the weighted average

Metalloids

B, Si, Ge, As, Sb, Te

Ionic Bonding

Cations and anions bind together via electrostatic attraction (usually metals and nonmetals)

Covalent Bonding

Atoms share electrons and form molecules (Usually between nonmetals)

Metals tend to form:

Cations

Nonmetals tend to form:

Anions

Group 1A’s charge

1+

Group 2A’s charge

2+

Group 7A’s charge

1-

Group 6A’s charge

2-

Group 5A’s charge

3-

Group 4A’s charge

4-

F₂

Flourine gas

H₂, N₂, O₂, F₂, Cl₂, He, Ne, Ar, Kr, Xe, Rn

Gases at room temperature (25 C)

Mono-

Means “1”

Di-

Means “2”

Tri-

Means “3”

Tetra-

Means “4”

Penta-

Means “5”

Hexa-

Means “6”

Hepta-

Means “7”

Octa-

Means “8”

Nona-

Means “9”

Deca-

Means “10”

Binary Compound

Has 2 Elements

Binary Covalent Compound/Acid

H + Non-metal

Ternary Covalent Compound/Acid

H + Polyatomic ions

Hydrates

Ionic compounds whose crystal lattices contain trapped H2O

Mixed Salts

H+ that can be replaced with any Group 1A cation, Na+, K+

3 Polyatomic Ions that can make Mixed Salts

Carbonate/CO₃^2-, Sulfate/SO₄^3-, Phosphate/PO₄^3-

Acids

Covalent compounds that can become ionic under the right conditions