Periodic Table Trends and Atomic Structure

Vocabulary practice flashcards covering metals, non-metals, metalloids, periodic trends (atomic radius, ionization energy, electronegativity), effective nuclear charge, shielding, and electron shell structure.

Periodic Law

The principle stating that physical and chemical properties of the elements are periodic functions of their atomic number, showing repeating patterns when elements are arranged in order of increasing atomic number (number of protons).

Metals

Elements located on the left and in the middle of the periodic table that are shiny, malleable, ductile, and good conductors of heat and electricity.

Non-metals

Elements located on the right side of the periodic table that are dull, brittle, poor conductors of electricity, and good insulators.

Metalloids

The $7$ elements located along the staircase of the periodic table (B, Si, Ge, As, Sb, Te, and At) that possess properties intermediate between metals and non-metals.

Atomic Radius

A measurement of atomic size that relates to reactivity (larger atoms being more reactive); it increases moving down a group due to more occupied energy levels and decreases from left to right across a period due to increased nuclear charge pulling on the same energy level.

Nuclear Charge

The electrostatic pull exerted by the positive protons in the nucleus on the surrounding electrons within an atom.

Effective Nuclear Charge

The net positive charge experienced by valence electrons from the nucleus, which takes into account electron shielding from inner orbitals as well as distance from the nucleus.

Shielding

The barrier effect where inner electron shells protect the outer valence electrons from the full attractive pull of the positive nucleus.

Ionization Energy

The amount of energy required to remove an electron from a gaseous atom (e.g., $Li \rightarrow Li^+ + 1e^-$); it increases across a period and decreases down a group.

Electronegativity

The tendency of an atom to attract electrons when chemically combined with another element, which increases across a period, decreases down a group, and reaches a peak value of $4.0$ in Fluorine.

Valence Electrons

The electrons located in the outermost shell or ring (furthest from the nucleus) of an atom that play a critical role in chemical bonding.

Group

A vertical column on the periodic table (columns $1$–$8$ or $1$–$18$) whose member atoms share the same number of valence electrons and similar chemical properties.

Period

A horizontal row on the periodic table whose member atoms contain the same number of occupied electron shells or energy levels.

Electron Shell Filling Rule

The rule specifying that the lowest energy shell must always be completely filled before adding electrons to the next higher shell, with maximum capacities of $2$ electrons in the $1\text{st}$ shell, $8$ electrons in the $2\text{nd}$ shell, and $18$ electrons in the $3\text{rd}$ shell.