Unit 5: Periodic Trends

Vocabulary flashcards covering the organization of the periodic table, element families, properties of matter, and periodic trends based on the Unit 5 study guide.

Periods

Horizontal rows on the periodic table; atoms in the same period have their valence electrons in the same energy level.

Groups (families)

Vertical columns on the periodic table numbered 1–18; elements within a group have the same number of valence electrons and similar properties.

Mendeleev

The scientist who arranged the first periodic table in order of increasing atomic mass.

Moseley

The scientist who demonstrated that elements should be ordered by increasing atomic number (number of protons), establishing the arrangement used in the modern periodic table.

Atomic number

The number of protons found in an atom.

Atomic mass

The average mass of an atom of an element, including its isotopes.

Alkali metals

Group 1 elements that possess 1 valence electron and have an electron configuration ending in $s^1$.

Alkaline earth metals

Group 2 elements that possess 2 valence electrons and have an electron configuration ending in $s^2$.

Transition metals

Elements located in groups 3–12 that belong to the d-block of the periodic table.

Inner transition metals

The f-block elements situated in the two rows displayed below the main periodic table.

Representative elements

The elements belonging to groups 1, 2, and 13–18, consisting of the s-block and p-block elements.

Halogens

Very reactive nonmetals in group 17 with 7 valence electrons.

Noble gases

Group 18 elements characterized by a full outer energy level and no defined electronegativity values.

Metals

Elements that are lustrous (shiny), malleable (can be hammered into sheets), ductile (can be drawn into wire), and good conductors of heat and electricity.

Ductile

The physical ability of a metal to be drawn into a wire.

Malleable

The property of a metal describing its ability to be hammered into sheets.

Nonmetals

Elements that are brittle as solids, dull, and poor conductors (insulators).

Metalloids (semiconductors)

Elements with intermediate properties between metals and nonmetals that conduct electricity at higher temperatures.

Atomic radius (size)

Half the distance between the nuclei of two like atoms bonded together; it decreases across a period and increases down a group.

First ionization energy (I.E.)

The energy needed to remove the most loosely held electron from a gaseous atom; it increases across a period and decreases down a group.

Electronegativity

The tendency of an atom to attract electrons when bonded to another atom; it increases across a period and decreases down a group.

Fluorine

The element possessing the greatest electronegativity value on the periodic table.

Shielding

The effect in which inner electrons block outer electrons from feeling the full positive charge of the nucleus.

Cations

Positive ions formed by the loss of electrons; they are always smaller than their corresponding neutral atoms.

Anions

Negative ions formed by the gain of electrons; they are always larger than their corresponding neutral atoms.

Successive ionization energies

The energies required to remove consecutive electrons; each subsequent value increases because the same nuclear charge holds fewer electrons, with a large jump occurring at the $(valence + 1)\text{th}$ electron.