Periodicity and the Periodic Table

A comprehensive set of vocabulary flashcards covering the history, organization, groups, and trends of the periodic table based on the teacher's lecture notes.

Periodicity

The recurring trends that are seen in the element properties.

Mendeleev

The scientist who arranged elements by increasing mass and used the resulting trends to predict undiscovered elements.

Moseley

The scientist whose experiments with X-rays led to the measurement of atomic numbers.

Modern Periodic Table Basis

Constructed by arranging elements in increasing order of their atomic numbers and electronic configuration in the outermost shells.

Ionization Energy

The amount of energy required to remove an electron from the ground state of a gaseous atom or ion.

Atomic Radius

Half the distance between the centers of two atoms that are touching each other, defined by the formula $\text{radius} = d/2$.

Electronegativity

A measure of the ability of an atom to form a chemical bond and attract electrons to itself when combined with another element.

Electron Affinity

The ability of an atom to accept an electron.

Groups

Vertical columns (numbered 1-18) also called families, where elements share similar properties and the same number of valence electrons.

Periods

Horizontal rows (numbered 1-7) where all elements have the same number of energy levels containing electrons.

Alkali Metals

Group 1 metals with 1 valence electron that are soft, have low density, and react violently with water.

Alkaline-Earth Metals

Group 2 metals with 2 valence electrons that are silver colored and very reactive, though less so than Group 1.

Transition Metals

Metals in Groups 3-12 that are good conductors of heat and electricity and have higher density than alkali or alkaline-earth metals.

Lanthanides

Rare earth elements with atomic numbers 58-71 that follow Lanthanum (#57) and possess high luster but tarnish easily.

Actinides

Rare earth elements with atomic numbers 90-103 that follow Actinium (#89); they are all radioactive and mostly lab-made.

Metalloids

Also known as semi-metals or semiconductors, these elements (including B, Si, Ge, As, and Te) have characteristics of both metals and nonmetals.

Chalcogens

The alternative name for elements in Group 16, which have 6 valence electrons.

Halogens

Very reactive Group 17 nonmetals with 7 valence electrons that react violently with alkali metals to form salts.

Noble Gases

Unreactive Group 18 nonmetals with a full outermost energy level (8 valence electrons, or 2 for He) that are colorless, odorless gases.

Hydrogen (H)

An element with 1 valence electron that stands apart because its properties are more similar to non-metals than metals.

Trend in Atomic Radius

Decreases as you go left to right across a period and increases as you go down a group.

Trend in First Ionization Energy

Generally gets harder to remove an electron across a row (period) and requires less energy going down a column (group).

Trend in Electronegativity

Increases going left to right across a period and decreases going down a group.