General Chemistry Chapter 2 - Atoms, Molecules, and Ions

List of Alkali Metals

Lithium, Sodium, Potassium, Rubidium, Cesium, Francium

Early Greek philosopher who thought that the world is made up of tiny indivisible particles called atomos


postulated the Atomic Theory

John Dalton

1st Postulate of Dalton's Atomic Theory

Each element is composed of extremely small particles called atoms

2nd Postulate of Dalton's Atomic Theory

All atoms of a given element are identical to one another in mass and other properties, but the atoms of one element are different from the atoms of all other elements

3rd Postulate of Dalton's Atomic Theory

The atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions

4th Postulate of Dalton's Atomic Theory

Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms

the smallest particles of an element that retain the chemical identity of the element


law of constant composition

in a given compound the relative numbers and kinds of atoms are constant

law of conservation of mass

the total mass of materials present after a chemical reaction is the same as the total mass present before the reaction

law of multiple proportions

if two elements A and B combine to form more than one compound, the masses of B that combine with a given mass of A are in the ratio of small whole numbers

J.J. Thomson

discovered electrons with his cathode ray tube experiments

SI unit for electrical charge


Robert Millikan

discovered the charge of an electron and thus its mass using the oil-drop experiment

plum-pudding model

created by J.J. Thomson; early description of an atom where electrons a embedded in an uniform positive sphere of matter

discovered the nucleus and the proton

Ernest Rutherford

discovered the neutron

James Chadwick

the electronic charge

1.062 x 10^-19 C

atomic mass unit

1.66054 x 10^-24 g

protons and neutrons are both approximately this many AMUs

approximately 1 AMU


10^-10 m

average diameter of an atom

100-500pm or 1-5 angstroms

the diameter of an atom is 2.2 angstroms; express this as picometer

220 pm

atomic number

the number of protons in the nucleus of an atom of any particular element

total number of protons plus neutrons in an atom

mass number

shown by the subscript to the left of an element's name

atomic number

mass number

shown by the superscript to the left of an element's name

all atoms of the same type of element have the same number of these


carbon-14 has this number of protons and neutrons

6 protons and 8 neutrons

carbon-11 has this number of protons and neutrons

6 protons and 5 neutrons


atoms with the same number of protons but different numbers of neutrons

4 basic forces of nature

gravitational, electromagnetic, strong nuclear, and weak nuclear forces

gravitational forces

attractive forces that act between all objects in proportion to their masses

electromagnetic forces

attractive or repulsive forces that act between either electrically charged or magnetically objects

strong nuclear forces

acts between subatomic particles as ini the nucleus; at distance it is stronger than the electromagnetic force

If the atomic number of strontium is 38, then strontium-90 has this many protons, neutrons, and electrons

38 protons, 38 electrons, and 52 neutrons

current definition of an AMU

assigning a mass of exactly 12 amu to an atom of the carbon-12 isotope

atomic weight

the average atomic mass of each element

how you calculate Atomic Weight

take percent of each isotope multiplied by its atomic mass in amu; then sum the products

when the periodic table was invented


horizontal rows on the periodic table


the number of elements in the 1st period of the periodic table

2 elements

the number of elements in the 2nd period of the periodic table

8 elements

the number of elements in the 3rd period of the periodic table

8 elements

vertical columns of the periodic table


the number of elements in the 4th period of the periodic table

18 elements

the number of elements in the 5th period of the periodic table

18 elements

the number of elements in the 6th period of the periodic table

32 elements

group 1 elements

Alkali Metals

group 2 elements

Alkaline Earth Metals

group 16 elements


group 17 elements


group 18 elements

Noble Gases

the number of elements in the 7th period of the periodic table

32 elements

List of Alkaline Earth Metals

Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium

List of Chalcogens

Oxygen, Sulfur, Selenium, Tellurium, Polonium, and Livermorium

List of Halogens

Fluorine, Chlorine, Bromine, Iodine, Astatine

List of Noble Gases

Helium, Neon, Argon, Krypton, Xenon, and Radon

diatomic molecules

molecule that is made up of 2 atoms


an assembly of two or more atoms tightly bound together

List of elements commonly found in nature as diatomic molecules

Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, and Iodine

molecular compound

compounds of more than one type of atom

molecular formulas

chemical formulas that indicate the actual numbers and types of atoms in a molecule

empirical formulas

chemical formulas that give only the relative number of atoms of each type in a molecule

structural formula

shows which atoms are attached to which within the molecule

ball-and-stick model

accurately represents the angles at which the atoms are attached to one another within a molecule


charged particle

ion with a positive charge


ion with a negative charge


polyatomic ions

atoms joined as a molecule yet have a net positive or negative charge

ionic compounds are usually a combination of these types of elements

combination of metal with a non-metal

how monatomic cations are named

have the same name as the metal and then add word "ion

monatomic ions

ions formed with a single atom

Name: Na+

Sodium ion

Name: Fe2+

Iron (II) ion or ferrous ion

Name: Fe3+

iron (III) ion or ferric ion

Name: Zn2+

zinc ion

Name: Cu+

copper (I) ion or cuprous ion

Name: Cu2+

copper (II) ion or cupric ion

Name: Al3+

aluminum ion

how polyatomic cations formed from nonmetals are named

names end in -ium and then add word ion

Name: NH4+

ammonium ion

Name: H3O+

hydronium ion

Name: H-

hydride ion

Name: O2-

oxide ion

Name: N3-

nitride ion

how monoatomic anions are named

replace endings with -ide and add word ion

Name: OH-

hydroxide ion

Name: CN-

cyanide ion

polyatomic anions containing oxygen


how oxyanions are named

the most common ion of the element ends in -ate. Ion with same charge but 1 fewer O ends with -ite.

Name: ClO4-

perchlorate ion

Name: ClO3-

chlorate ion

Name: ClO2-

chlorite ion

Name: ClO-

hypochlorite ion

Name: NO3-

nitrate ion

Name: NO2-

nitrite ion

Name: SO4-

sulfate ion

Name: SO3-

sulfite ion

Name: PO43-

phosphate ion

how anions derived by adding H+ to an oxyanion

add prefix and word hydrogen

Name: HCO3-

hydrogen carbonate ion or bicarbonate ion

Name: H2PO4-

dihydrogen phosphate ion

Name: CH3COO-

acetate ion

how ionic compounds are named

list cation name followed by the anion name

Name: CaCl2

calcium chloride

Name: Al(NO3)3

aluminum nitrate

Name: K2SO4

potassium sulfate

Name: FeCl3

Iron (III) chloride

Name: Co(NO3)2

cobalt (II) nitrate

Name: Ca(HCO3)2

calcium hydrogen carbonate

Name: HCl

hydrochloric acid

Name: H2S

hydrosulfuric acid

Name: HClO4

perchloric acid

Name: HClO3

chloric acid

Name: HClO2

chlorous acid

Name: HClO

hypochlorous acid

how acids are named

Use the anion name. Change -ide to -ic and add prefix hydro-. For oxyanions change -ate to -ic and -ite to -ous.

Name: HCN

hydrocyanic acid (l) or hydrogen cyanide (g)

Name: HNO3

nitric acid

Name: H2SO4

sulfuric acid

Name: H2SO3

sulfurous acid

the formula for hydrobromic acid


the formula for carbonic acid


how binary molecular compounds are named

The element farthest left and then down a group is named first. Then the second element is given a -ide ending. Then add Greek prefixes equal to number of atoms. Mono- is not used in the first element.

Name: Cl2O

dichlorine monoxide

Name: NF3

nitrogen trifluoride

Name: P4S10

tetraphosphorous decasulfide

Name: N2O4

dinitrogen tetroxide

Name: SO2

sulfur dioxide

Name: PCl5

phosphorous pentachloride

the formula for disulfur dichloride



compounds that contain only carbon and hydrogen

basic class of hydrocarbons where each carbon is bonded to four atoms


Name: CH4


Name: C2H6


Name: C3H8


Name: GaF3

gallium (III) fluoride

Name: LiH

lithium hydride

Name: KClO4

potassium perchlorate

Name: HBrO3

bromic acid

Name: HBr

hydrobromic acid

Name: H3PO4

phosphoric acid

the formula for hypochlorous acid


the formula for iodic acid


the formula for sulfurous acid


Name: SF6

sulfur hexaflouride

Name: IF5

iodine pentaflouride

Name: XeO3

xenon trioxide

formula for dinitrogen tetroxide


formula for tetraphosphorous hexasulfide


the number of protons, electrons, and neutrons in helium-3

2 protons, 2 electrons, and 1 neutron