Chapter 7: Periodic Properties of the Elements

A comprehensive set of vocabulary flashcards covering key terms and definitions from Chapter 7, Periodic Properties of the Elements.

Periodicity

The repetitive pattern of elemental properties as a function of atomic number.

Dmitri Mendeleev

Chemist who arranged elements by atomic mass and chemical properties, predicting missing elements such as germanium.

Lothar Meyer

Scientist who independently reached conclusions similar to Mendeleev about grouping elements in the periodic table.

Henry Moseley

Physicist who experimentally established atomic number as the fundamental basis of the periodic table.

Atomic Number (Z)

The number of protons in an atom’s nucleus, determining its position in the periodic table.

Effective Nuclear Charge (Zeff)

The net positive charge experienced by valence electrons, approximated by Zeff = Z – S.

Screening Constant (S)

Approximate measure of inner-electron shielding used to estimate effective nuclear charge.

van der Waals Radius

Half the shortest distance between nuclei of two non-bonded, colliding atoms; also called the nonbonding atomic radius.

Bonding Atomic Radius

Half the internuclear distance between two bonded atoms of the same element.

Cation

A positively charged ion, smaller than its parent atom because it has lost electrons.

Anion

A negatively charged ion, larger than its parent atom because it has gained electrons.

Isoelectronic Series

A group of ions or atoms that contain the same number of electrons; size decreases with increasing nuclear charge.

Ionization Energy (I)

Minimum energy required to remove an electron from a gaseous atom or ion.

First Ionization Energy (I1)

Energy needed to remove the first electron from a neutral gaseous atom.

Electron Affinity

Energy change when an electron is added to a gaseous atom; typically exothermic (negative value).

Metallic Character

Degree to which an element exhibits properties of metals; increases down a group and decreases across a period.

Metals

Elements that are shiny, conductive, malleable, ductile, usually solid at room temperature, and tend to form cations.

Nonmetals

Elements that are dull, brittle (as solids), poor conductors, and tend to form anions; may exist as solids, liquids, or gases.

Metalloids

Elements with mixed metallic and nonmetallic properties; several function as semiconductors.

Alkali Metals (Group 1A)

Soft, low-density metals with very low ionization energies that react vigorously with water.

Alkaline Earth Metals (Group 2A)

Metals with higher densities and melting points than alkali metals and moderately low ionization energies.

Halogens (Group 7A)

Highly reactive nonmetals with large negative electron affinities that form metal halides.

Noble Gases (Group 8A)

Monatomic gases with very high ionization energies and positive electron affinities, making them largely unreactive.

Oxygen Group (Group 6A)

Family in which O, S, Se are nonmetals, Te is a metalloid, and Po is metallic, showing increased metallic character down the group.

Superoxide (O2⁻)

An oxygen species formed by heavier alkali metals (K, Rb, Cs) reacting with O₂; contains the O₂⁻ ion.

Peroxide (O₂²⁻)

Oxygen species produced when sodium reacts with O₂, featuring the O₂²⁻ ion.

Basic Oxide

Metal oxide that reacts with water to form a base; characteristic of most metal oxides.

Acidic Oxide

Nonmetal oxide that reacts with water to form an acid; typical of many nonmetal oxides.

Flame Test

Qualitative method for identifying alkali metals by their characteristic flame colors.

Effective Nuclear Charge Trend

Zeff increases across a period and decreases down a group.

Atomic Radius Trend

Bonding atomic radius decreases across a period and increases down a group.

Ionization Energy Trend

First ionization energy increases across a period and decreases down a group, with minor irregularities.

Electron Affinity Trend

Generally becomes more negative across a period with small changes down a group; exceptions include Groups 2A, 5A, 8A.

Relative Size: Cations vs. Atoms vs. Anions

For a given element, cations are smaller than the neutral atom, while anions are larger.

Semiconductors

Metalloids (e.g., Si, Ge) whose electrical conductivity is intermediate between metals and insulators, useful in computer chips.