Chemistry 122 - Chapter 2 Vocabulary Flashcards

Vocabulary practice flashcards covering fundamental terms, subatomic particles, isotopes, periodic table organization, and mole conversions from Chapter 2.

J. J. Thomson

Scientist who discovered the electron in 1897 using a cathode ray tube, demonstrating that atoms contain negatively charged particles with a constant mass-to-charge ratio.

Millikan's Oil-Drop Experiment

An experiment performed by Robert Millikan in 1909 that determined the charge ($e = -1.602 \times 10^{-19}\,\text{C}$) and mass ($m_e = 9.109 \times 10^{-31}\,\text{kg}$) of an electron.

Plum-Pudding Model

An atomic model proposed by J. J. Thomson in which electrons are distributed throughout a diffuse, positively charged sphere.

Radiation

The spontaneous emission of high-energy radiation and particles by radioactive materials.

Beta particles

High-energy electrons ($\beta$) emitted by radioactive substances.

Alpha particles

Radioactive particles ($\alpha$) possessing a $2+$ charge and a mass equal to that of a helium nucleus.

Nuclear Atom Model

An atomic model established following Rutherford's gold foil experiment that assumes a tiny, dense, positively charged nucleus containing nearly all the mass of the atom.

Proton

A positively charged subatomic particle found in the nucleus with a mass of approximately $1.00728\,\text{u}$ and a relative charge of $1+$.

Neutron

An electronically neutral subatomic particle found in the nucleus with a mass of approximately $1.00866\,\text{u}$.

Unified atomic mass unit (u)

A unit of mass equal to $\frac{1}{12}$ of the mass of a carbon atom containing 6 protons and 6 neutrons ($12\,\text{u}$); also known as daltons ($\text{Da}$).

Isotopes

Atoms of an element containing the same number of protons but different numbers of neutrons.

Atomic number (Z)

The number of protons in an atom's nucleus, which represents its nuclear charge and uniquely identifies the element.

Mass number (A)

The total number of protons plus neutrons in a nuclide.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Periods

The horizontal rows numbered $1\text{--}7$ on the periodic table.

Groups

The vertical columns numbered $1\text{--}18$ on the periodic table; also known as families.

Metals

Elements that are shiny, solid (with the exception of liquid mercury), malleable, ductile, and good conductors of heat and electricity.

Nonmetals

Elements that exist as brittle solids, liquids, or gases and do not conduct heat or electricity.

Metalloids

Elements that exhibit properties intermediate between metals and nonmetals, being shiny but brittle, and acting as semiconductors; also called semimetals.

Average Atomic Mass

The value calculated by taking the weighted average of the masses of all naturally occurring isotopes of an element.

Molecular mass

The sum of all the average atomic masses of the atoms chemically bonded together in a single molecule.

Formula mass

The mass calculated for ionic compounds by summing the atomic masses of the atoms in its formula unit.

Mole

The SI unit for expressing quantities of substances, defined as the number of atoms in exactly $12\,\text{g}$ of carbon-12, equal to $6.022 \times 10^{23}$ particles (Avogadro's constant).

Molar Mass (M)

The mass in grams of one mole of a substance (atom, molecule, or formula unit), expressed in units of $\text{g/mol}$.