CHEM 1670 Iowa State Chapter 2

Chapter 2 key terms from "Brown/Holme's Chemistry for Engineering Students"

polymers

Long chain molecule formed by linking together a large number of smaller molecules. Most common polymers are organic compounds.

monomers

The small repeating unit from which a polymer molecule is made.

Polyethylene

Polymer with the repeating unit —CH2CH2—, used in applications ranging from milk jugs to bullet-proof vests.

poly(vinyl chloride)

Polymer with the repeating unit —CH2CHCl—, frequently used in plastic pipes.

polyacetylene

Polymer with the repeating unit CH=CH, which can be made electrically conducting by doping.

nucleus

The small, dense core of an atom, containing neutrons and protons.

electrons

Negatively charged subatomic particle.

protons

Positively charged subatomic particle found in an atom’s nucleus. Also H+ ions.

neutrons

Electrically neutral subatomic particle found in an atom’s nucleus.

atomic number

The number of protons in the nucleus of an atom of a particular element.

atomic mass unit

Unit used to express the relative masses of atoms. The amu is defined as one-twelfth the mass of an atom of C12, and 1amu=1.6606×10-24g.

amu

Unit used to express the relative masses of atoms. The amu is defined as one-twelfth the mass of an atom of C12, and 1amu=1.6606×10-24g.

mass number

The combined total of protons and neutrons in an atom.

isotopes

Any of two or more forms of the same element that have different numbers of neutrons.

isotopic abundances

The percentage of the atoms in a naturally occurring sample of an element that consists of a specified isotope.

atomic weight

The average mass in amu of an atom in a sample of a particular element.

ion

An atom or group of atoms with a net electrical charge.

monatomic ion

Charged particle formed when a single atom gains or loses one or more electrons.

Like 1 positively charged oxygen.

polyatomic ions

A group of atoms that carries an electrical charge.

Like 2 positively charged oxygen or like 1 negatively charged atom of cobalt and nitrogen.

anions

A negatively charged atom or group of atoms.

cation

A positively charged atom or group of atoms.

Coulomb’s law

Mathematical description of the force between two charged particles.

chemical bonds

Attractive force between two atoms holding them together to form a molecule or a part of a molecule.

chemical compound

A pure substance made up of atoms of two or more elements joined together by chemical bonds.

molecules

Two or more atoms joined together by chemical bonds, forming the smallest particle that retains the chemical properties of a substance.

chemical formula

Symbolic description of a molecule or compound showing its constituent elements and the relative number of each.

molecular formula

Chemical formula showing the number of atoms of each element in one molecule of a compound.

empirical formula

Chemical formula that shows the composition of a compound in terms of the simplest whole-number ratio of the atoms of each element.

lattice

A regular, periodic arrangement of atoms, ions, or molecules in a crystalline solid.

ionic bonding

Bonding in which one or more electrons are transferred from one species to another.

formula unit

The smallest whole number ratio of anions and cations in an ionic compound.

metallic bonding

Bonding in a solid metal, where the nuclei and some fraction of their electrons comprise a positively charged “core” localized at these lattice points, and valence electrons form a surrounding “sea” of negative charge.

covalent bonding

Attractive force resulting from the sharing of electrons between pairs of atoms.

periodicity

Regular patterns in the chemical and physical behavior of groups of elements.

periodic law

When the elements are arranged by atomic number, they display regular and periodic variation in their chemical properties.

periods

Horizontal row of the periodic table.

groups

Vertical column of the periodic table.

alkali metals

Elements of Group 1, the first column of the periodic table, except hydrogen: Li, Na, K, Rb, Cs, and Fr.

alkaline earth metals

Elements of Group 2, the second column of the periodic table: Be, Mg, Ca, Sr, Ba, and Ra.

halogens

The elements in Group 17 of the periodic table: F, Cl, Br, I, and At.

noble gases

Element in Group 18 of the periodic table: He, Ne, Ar, Kr, Xe, or Rn. Also called rare gas.

representative elements

Element of Groups 1, 2, and 13–18, for which the highest lying valence electron occupies an s or p orbital. Also called main group element.

transition metals

Element in Groups 3 through 12 of the periodic table, in which valence electrons occupy d orbitals.

lanthanides

Any of the elements from cerium through lutetium, whose valence electrons are in the 4f subshell. They appear as the first row of elements below the main body of the periodic table.

actinides

Any of the elements from thorium through lawrencium, with valence electrons in the 5f subshell. Appears in the second row of elements below the main body of the periodic table.

metals

An element that is malleable, ductile, conducts electricity, and tends to form cations in its chemical compounds.

Nonmetals

An element that does not display the chemical and physical properties of metals.

metalloids

An element that displays some properties of metals and some properties of nonmetals. Sometimes called a semimetal.

organic chemistry

The study of compounds of the element carbon.

Inorganic chemistry

The study of all elements, besides carbon, and their compounds.

line structure

Visual representation of organic compounds in which carbon atoms and the hydrogen atoms attached to them are not shown explicitly.

functional group

An atom or group of atoms that imparts characteristic chemical properties to any organic compound in which it is found.

hydrocarbons

Chemical compound containing only carbon and hydrogen atoms.

chemical nomenclature

The systematic assignment of names to chemical compounds on the basis of their constituent elements or ions and their structures.

binary compounds

Any chemical substance containing two different elements.

oxyanions

Polyatomic anion that contains oxygen.

free radicals

Extremely reactive chemical species containing one or more unpaired electrons.

high-density polyethylene (HDPE)

Form of polyethylene featuring long, straight chain molecules. Because these chains pack together more tightly, HDPE is harder and stronger than low-density polyethylene.

low-density polyethylene (LDPE)

Form of polyethylene featuring branched chain molecules. Because these chains do not pack together as tightly, LDPE is softer and more flexible than high-density polyethylene.

ultra-high molecular weight polyethylene (UHMWPE)

Polyethylene consisting of extremely long polymer chains and displaying unusually high strengt