Atoms and Elements

Flashcards for reviewing Atoms and Elements lecture notes.

Atomos

Greek for indivisible, referring to the idea that matter is ultimately composed of tiny, indestructible units.

Atomic Theory of Matter

The theory that atoms are the fundamental building blocks of matter, reintroduced in the 19th century by John Dalton.

Dalton's First Postulate

Each element is composed of extremely small particles called atoms.

Dalton's Second Postulate

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

Dalton's Third Postulate

Atoms of an element are not changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions.

Dalton's Fourth Postulate

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

Law of Constant Composition

Also known as the law of definite proportions, states that the elemental composition of a pure substance never varies.

Law of Conservation of Mass

The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place.

Law of Multiple Proportions

Two elements, A & B, can combine in any ratio, as long as the ratio is a whole number.

Electron

Negatively charged particles discovered emanating from cathode tubes; J.J. Thompson is credited with their discovery in 1897.

Millikan Oil Drop Experiment

Experiment by Robert Millikan that determined the charge on the electron in 1909.

Radioactivity

The spontaneous emission of radiation by an atom, first observed by Henri Becquerel and studied by Marie and Pierre Curie.

Types of Radiation

Three types of radiation discovered by Ernest Rutherford: alpha particles, beta particles, and gamma rays.

Plum Pudding Model

An outdated model of the atom envisioned as a positive sphere of matter with negative electrons embedded in it.

Discovery of the Nucleus

Experiment where Ernest Rutherford shot alpha particles at a thin sheet of gold foil, leading to the discovery of the nucleus.

The Nuclear Atom

A very small, dense center of the atom with electrons existing around the outside of the atom. Most of the volume of the atom is empty space.

Proton

The subatomic particle discovered by Rutherford in 1919 that has a positive charge

Neutron

The subatomic particle discovered by James Chadwick in 1932 that has no charge.

Atomic Number (Z)

The number of protons in the nucleus of an atom, determining the identity of an element.

Mass Number

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of the same element with different masses due to varying numbers of neutrons.

Atomic Mass

The mass of an atom in atomic mass units (amu), approximately equal to the number of protons and neutrons.

Average Atomic Mass

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

Periods

Horizontal rows on the periodic table.

Groups

Vertical columns on the periodic table; elements in the same column have similar chemical properties.

Alkali metals

Elements in Group 1A (Li, Na, K, Rb, Cs, Fr)

Alkaline earth metals

Elements in Group 2A (Be, Mg, Ca, Sr, Ba, Ra)

Chalcogens

Elements in Group 6A (O, S, Se, Te, Po)

Halogens

Elements in Group 7A (F, Cl, Br, I, At)

Noble gases

Elements in Group 8A (He, Ne, Ar, Kr, Xe, Rn)

Metalloids

Border the stair-step line on the periodic table (with the exception of Al and Po).

Subscript in Chemical Formulas

Subscript to the right of the symbol of an element, indicating the number of atoms of that element in one molecule of the compound.

Molecular Compounds

Substances composed of molecules and almost always contain only nonmetals.

Diatomic Molecules

Molecules containing two atoms of the same element (H2, N2, O2, F2, Cl2, Br2, I2).

Empirical Formulas

Formulas that give the lowest whole-number ratio of atoms of each element in a compound.

Molecular Formulas

Formulas that give the exact number of atoms of each element in a compound.

Ion

A charged atom or group of atoms formed by the loss or gain of electrons

Formulas from Ionic Charges

The charge on the cation becomes the subscript on the anion, and vice versa; divide by the greatest common factor if necessary.

Cation Naming

Positive charge, usually a metal; named as the element.

Anion Naming

Negative charge, usually a nonmetal; named as the element, but end name in -ide.

Naming Variable Charge Metals

Metals with two or more positive ions (cations) use a Roman numeral to identify ionic charge.

Polyatomic Ions

Ions that are composed of more than one atom

Naming compounds with Polyatomic ions

Use element name for metal, with Roman numeral if needed, followed by name of polyatomic ion

Nomenclature of Binary Compounds

The less electronegative atom is usually listed first with a prefix denoting the number of atoms of each element in the compound; the ending on the more electronegative element is changed to -ide

Acid Nomenclature (-ide)

If the anion in the acid ends in - ide, change the ending to -ic acid and add the prefix hydro-

Acid Nomenclature (-ate)

If the anion in the acid ends in - ate, change the ending to -ic acid

Acid Nomenclature (-ite)

If the anion in the acid ends in - ite, change the ending to -ous acid