Chemistry Unit 2: Atomic Structure & Nuclear Chemistry

Vocabulary terms, nuclear equations, electron configurations, and foundational concepts covering Atomic Structure and Nuclear Chemistry.

Ernest Rutherford

The scientist who performed the Gold Foil Experiment, demonstrating that an atom has a dense nucleus and consists mostly of empty space.

Atomic Orbital Capacity

The principle that any single atomic orbital can hold a maximum of $2$ electrons.

Ion

An atom or group of bonded atoms that possesses a net electrical charge due to an unequal number of protons and electrons.

Isotopes

Atoms of the same element that share the same atomic number (number of protons) but have different numbers of neutrons and different mass numbers.

Average Atomic Mass

The decimal value listed on the Periodic Table representing the weighted average mass of an element's naturally occurring isotopes, calculated as: $\text{Average Mass} = \frac{\text{Mass}_1 \times \text{Abundance}_1 + \text{Mass}_2 \times \text{Abundance}_2 + \text{Mass}_3 \times \text{Abundance}_3}{100}$.

Atomic Structure

The fundamental composition of an atom, featuring a central, positively charged nucleus surrounded by negatively charged electrons.

Electrically Neutral Atom

An atom with no net electrical charge because its total number of positively charged protons is exactly equal to its total number of negatively charged electrons.

Atomic Number

The number of protons in an atom's nucleus, which also equals the total number of electrons in an electrically neutral atom.

Half-Life Independence

The characteristic property of radioactive decay where the length of a radioisotope's half-life remains constant regardless of external temperature changes such as heating.

Gamma Ray

A form of high-frequency electromagnetic radiation emitted during nuclear decay that consists solely of energy, having neither mass nor charge.

Radiation Penetrating Power

The relative ability of nuclear emissions to pass through matter, ranked from least penetrating to greatest penetrating power: alpha particle ($\text{least}$), beta particle, gamma ray ($\text{greatest}$).

Dalton's Atomic Theory

An early fundamental chemical theory postulating that all atoms of a given element are identical in mass and properties.

Beta Decay

A type of radioactive decay in which an unstable nucleus emits a beta particle (high-energy electron), represented by the equation: $^{14}_{6}\text{C} \rightarrow\text{ }^{14}_{7}\text{N} +\text{ }^{0}_{-1}\text{e}$.

Alpha Decay

A type of radioactive decay in which an unstable nucleus emits an alpha particle (helium-4 nucleus), represented by the equation: $^{222}_{86}\text{Rn} \rightarrow\text{ }^{218}_{84}\text{Po} +\text{ }^{4}_{2}\text{He}$.

Neutron Count in Fluorine-19 ($^{19}_{9}\text{F}$)

The quantity of neutrons found by subtracting the atomic number from the mass number: $19 - 9 = 10\text{ neutrons}$.

Electron Configuration of Strontium (Sr)

The full longhand electron arrangement for strontium ($Z = 38$): $1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,4s^2\,3d^{10}\,4p^6\,5s^2$, which gives strontium $2$ valence electrons.

Shorthand Electron Configuration of Antimony (Sb)

The abbreviated noble gas core electron configuration for antimony ($Z = 51$): $[\text{Kr}]\,5s^2\,4d^{10}\,5p^3$, containing $5$ valence electrons.

Valence Electrons of Sulfur (S)

The total number of electrons in sulfur's outermost principal energy level ($3s^2\,3p^4$), equal to $6$ valence electrons.

Half-Life Decay of Potassium-42

The radioactive decay calculation for a $750\text{ g}$ sample of potassium-42 with a half-life of $12.4\text{ hours}$ over $62.0\text{ hours}$ ($5$ half-lives): $\frac{750\text{ g}}{2^5} = 23.4\text{ g}$ remaining.