Atomic Theory, Periodic Table, and Electronic Structure

Vocabulary flashcards covering atomic structure, subatomic particles, isotopes, atomic mass calculations, periodic table element groups, and electronic quantum structures.

Atomic Theory

The principle that all matter is composed of small, indivisible atoms that retain their identity during chemical reactions, differ between elements, combine in simple fixed whole-number ratios, and are rearranged rather than created or destroyed in chemical reactions.

Proton

A positively charged subatomic particle located inside the central nucleus of an atom, possessing a relative charge of $+1$ and a mass of $1.0073\,amu$.

Neutron

A neutral subatomic particle located inside the central nucleus of an atom, possessing a charge of $0$ and a mass of $1.0087\,amu$.

Electron

A negatively charged subatomic particle moving outside the nucleus, possessing a relative charge of $-1$ and a mass of $5.486 \times 10^{-4}\,amu$.

Nucleus

The extremely dense central location of an atom containing positively charged protons and neutral neutrons, accounting for nearly all of the atom's mass.

Nuclear Strong Force

The fundamental attractive force that binds protons and neutrons together within the atomic nucleus.

Atomic Number (Z)

The integer representing the total number of protons in an atom, which uniquely determines the element's identity and equals the number of electrons in a neutral atom.

Mass Number (A)

The total sum of protons ($Z$) and neutrons ($N$) in an atom's nucleus, calculated as $A = Z + N$.

Isotopes

Different forms of atoms of the same element containing the same number of protons (same atomic number) but different numbers of neutrons (different mass number).

Atomic Mass

The actual mass of an individual atom expressed in atomic mass units ($amu$), defined relative to the mass of carbon-12 ($^{12}\text{C} = 12\,amu$ exactly).

Atomic Mass Unit (amu)

Also known as a Dalton ($Da$), a unit of mass defined relative to the mass of a carbon-12 atom.

Atomic Weight

The weighted average of the atomic masses of an element's naturally occurring isotopes based on their relative abundances, as displayed on the periodic table.

Alkali Metals (Group 1A)

Soft, shiny metals with low densities and low melting points (Li, Na, K, Rb, Cs, Fr) that react vigorously with water to form alkaline (basic) solutions.

Alkaline Earth Metals (Group 2A)

Soft, silvery metals with relatively higher melting points (Be, Mg, Ca, Sr, Ba, Ra) that are relatively less reactive and form alkaline solutions.

Halogens (Group 7A)

Corrosive nonmetals existing as colorful gases, liquid, and solids (F, Cl, Br, I, At) that react vigorously with metals.

Noble Gases (Group 8A)

Colorless nonmetal gases (He, Ne, Ar, Kr, Xe, Rd) that are chemically inert and do not react with other elements.

Wave-Particle Duality

The quantum mechanical concept defining an electron as possessing properties of both a particle and a wave.

Quantized Energy

Energy restricted to discrete, fixed values rather than a continuous range, dictating the specific allowed energy levels and locations of electrons within an atom.

Shells

Principal energy levels designated by quantum number $n$ around the nucleus; higher $n$ values indicate larger shells, higher energy electrons, and maximum electron capacities of $2n^2$.

Subshells

Energy sublevels within principal shells designated by letters s, p, d, and f, holding maximum electron capacities of $2$, $6$, $10$, and $14$ electrons respectively.

Orbital

A region of space around the nucleus defined by quantum mechanical wave functions that represents the highest probability of finding an electron, holding no more than 1 pair of electrons.