AP Chemistry Periodic Trends and Explanations Flashcards

Vocabulary flashcards covering periodic trends, Coulomb's Law, justification methods, ionization energy exceptions, ionic radii, and elemental reactivity based on lecture notes.

Coulomb's Law

A physical law stating that the force of attraction between two oppositely charged particles is directly proportional to the magnitude of the charges and inversely proportional to the square of the distance between them: $F = k \frac{(Q_+)(Q_-)}{d^2}$.

Effective Nuclear Charge ($Z_{eff}$)

The net positive nuclear pull experienced by valence electrons, used primarily to justify periodic trends across a period.

Principal Energy Level ($n$)

The main energy shell occupied by electrons; an increase in $n$ increases the distance over which the nucleus must attract valence electrons, used to justify trends down a group.

Atomic Radius

The distance between the nucleus and the outer edge of the electron cloud in a neutral atom.

Ionization Energy

The energy needed to remove an electron from a gaseous atom or ion, which is always an endothermic process.

Group II to Group III Ionization Energy Exception

A drop in first ionization energy occurring between groups II and III because $p$ electrons do not penetrate the nuclear region as greatly as $s$ electrons and are therefore not as tightly held.

Group V to Group VI Ionization Energy Exception

A drop in first ionization energy occurring between groups V and VI because the increased repulsion created by the first pairing of electrons in the $p$-orbitals outweighs the increase in $Z_{eff}$.

Electron Affinity

The energy change associated with the addition of an electron to a gaseous atom, which can be exothermic (indicating a stable negative ion) or endothermic.

Electronegativity

An assigned property indicating the attraction of an atom for the pair of outer shell electrons in a covalent bond with another atom.

Ionic Radius

The distance from the nucleus to the outer edge of the electron cloud in a charged ion.

Electron-Electron Repulsion

The repulsive force between negatively charged electrons; an increase in this force causes the electron cloud to expand, whereas a decrease allows the cloud to contract.

Shielding

The barrier effect provided by full inner energy levels between the nucleus and valence electrons, keeping $Z_{eff}$ somewhat constant within a column.

Successive Ionization Energies

The increasing energy required to remove additional electrons sequentially from an atom, as each electron is removed from an increasingly positive species with less electron-electron repulsion.

Metal Reactivity

The tendency of metals to react by losing electrons, which increases down a column as an increased principal energy level ($n$) creates greater distance and weakens Coulombic attraction.

Non-metal Reactivity

The tendency of non-metals to react by gaining electrons, which increases up a column and across a period due to higher $Z_{eff}$ and smaller principal energy level ($n$) creating a stronger nuclear pull.