CHAPTER 2 Atoms, Molecules, and Ions

alpha particle (α particle)

positively charged particle consisting of two protons and two neutrons

1904 Thomson proposed the "plum pudding" model of atoms

described a positively charged mass with an equal amount of negative charge in the form of electrons embedded in it, since all atoms are electrically neutral.

atomic number (Z)

the number of protons in the nucleus of an atom

mass number (A)

The sum of the number of neutrons and protons in an atomic nucleus

Isotopes

Atoms of the same element that have different numbers of neutrons

average mass

calculated from the isotopes of an element weighted by their relative abundances

Mass spectrometry (MS)

An instrumental method for identifying the chemical constituent of a substance by means of the separation of gaseous ions according to their differing mass and charge

molecular formula

a chemical formula that shows the kinds and numbers of atoms present in a molecule of a compound

empirical formula

a formula with the lowest whole-number ratio of elements in a compound (does not accirately represent compound)

isomers

compounds with the same chemical formula but different molecular structures

periodic law

the properties of the elements are periodic functions of their atomic numbers.

A modern periodic table arranges

elements in increasing order of their atomic numbers and groups atoms with similar properties in the same vertical column

Periods (series)

Seven horizontal rows

Groups

18 vertical columns

metals

elements that are shiny, malleable, good conductors of heat and electricity

nonmetals

elements that appear dull and are poor conductors of heat and electricity

metalloids

elements that conduct heat and electricity moderately well, and possess some properties of metals and some properties of nonmetals

main-group elements (representative elements)

elements in groups 1-2 and 13-18

transition metals

elements in groups 3-12

inner transition metals

lanthanides and actinides

alkali metals

Group 1

Alkali earth metals

Group 2

Pnictogens

Group 15

chalcogens

Group 16

halogens

Group 17

noble gases (inert gases)

Group 18

ionic bonds

electrostatic forces of attraction, between objects of opposite electrical charge (cations and anions)

covalent bonds

attractive forces between the positively charged nuclei of the bonded atoms and one or more pairs of electrons that are located between the atoms

-ate suffix

polyatomic ions with more oxygen atoms

-ite suffix

polyatomic ions with fewer oxygen atoms than -ate

per- prefix (highest)

polyatomic ions with one more oxygen than -ate

hypo- prefix (lowest)

polyatomic ions with one less oxygen than -ite

ionic compounds

compounds composed of cations and anions

molecular compounds

formed by a combination of nonmetals

molecular compounds often exist as

gases, low boiling liquids, low melting solids

Nomenclature

a collection of rules for naming things

Hydrate

Ionic compounds that contain water molecules as integral components of their crystals

mono-

1 prefix

di-

2 prefix

tri-

3 prefix

tetra-

4 prefix

penta-

5 prefix

hexa-

6 prefix

hepta-

7 prefix

octa-

8 prefix

nona-

9 prefix

deca-

10 prefix

binary acids

composed of hydrogen and a nonmetal

Oxyacids

acids that contain hydrogen, oxygen, and a third element (usually a nonmetal)

Fe2+

ferrous ion iron(II) ion

Fe3+

ferric ion iron(III) ion

Cu+

cuprous ion copper(I) ion

Cu2+

cupric ion copper(II) ion