Atomic Theory and the Periodic Table

Vocabulary flashcards covering atomic theory, atomic structure, isotopes, and the periodic table, based on the provided lecture notes.

Atom

The smallest particle that an element can be divided into and still be identifiable, from the Greek atomos, meaning "indivisible."

Atomic Theory

A set of assumptions proposed to explain the chemical behavior of matter: all matter is composed of atoms; atoms of a given element differ from atoms of all other elements; chemical compounds consist of atoms combined in specific, fixed ratios; chemical reactions change only the way atoms are combined, atoms are unchanged.

Subatomic Particles

Small particles that are the building blocks making up atoms.

Proton

A subatomic particle located in the nucleus with a mass of 1.007276 amu and a charge of +1; it is responsible for Element ID.

Neutron

A subatomic particle located in the nucleus with a mass of 1.008665 amu and a charge of 0; it influences radioactive properties.

Electron

A subatomic particle located in shells around the nucleus with a mass of 5.485799 x 10-4 amu and a charge of -1; it dictates chemical properties.

Atomic Mass Unit (amu)

A relative number, defined as 1/12 of a carbon nucleus (1 p or 1 n) equal to 1.660539 x 10-24 g, also called Dalton.

Nuclear Strong Force

The force that holds protons and neutrons together in the nucleus.

Atomic Number (Z)

The number of protons in atoms of a given element.

Mass Number (A)

The sum of the protons and neutrons in an atom.

Element (Revised Definition)

A pure substance in which all atoms have the same atomic number.

Isotopes

Atoms of the same element (same number of protons) with different numbers of neutrons, thus having the same atomic number but different mass numbers.

Atomic Mass

The weighted average of an element’s atoms, calculated by considering the mass and abundance of its isotopes.

Periodic Table

A graphic display of the elements in order of increasing atomic number; elements with similar properties fall into columns.

Groups (or Families)

The 18 vertical columns on the periodic table, containing elements with similar properties.

Periods

The 7 horizontal rows on the periodic table, characterized by increasing atomic number across them.

Metals

Elements typically found on the left side of the periodic chart, which are mostly solids at room temperature (except Hg), malleable, and good conductors of heat and electricity.

Non-Metals

Elements typically found on the right side of the periodic chart, which exist in various phases at room temperature and are not good conductors of heat or electricity.

Metalloids

Elements having properties between those of metals and non-metals.

Alkali Metals (Group 1A)

Shiny, lustrous, soft, silvery metals with low melting points that react strongly with water; never found as single atoms in nature.

Alkaline Earth Metals (Group 2A)

Lustrous metals that are solids at room temperature and are less reactive than Group 1A elements; never found as single atoms in nature.

Halogens (Group 7A)

Colorful, corrosive non-metals that exist in various phases at room temperature; never found as single atoms in nature.

Noble Gases (Group 8A)

Colorless, odorless, tasteless gases at room temperature that exhibit little reactivity; never found as single atoms in nature.

Periodicity

A pattern seen in elemental properties, such as atomic radius, that shows a regular rise-and-fall pattern across periods, with maxima for Group 1A and minima for Group 7A elements.