Periodic Table VOCAB

Periodic Table

A structured, grid-like arrangement of chemical elements ordered by increasing atomic number that highlights recurring physical and chemical trends.

Element

A pure substance that cannot be broken down or decomposed into simpler substances by ordinary chemical or physical means.

Period

A horizontal row of elements in the periodic table. The period number corresponds to the total number of occupied electron energy shells/orbits in an atom.

Group (or Chemical Family)

A vertical column of elements in the periodic table. Elements in the same group share identical numbers of valence electrons and exhibit similar physical and chemical properties.

Alkali Metals

The metallic elements located in Group 1 (excluding hydrogen). They are soft, silver-coloured, highly reactive metals with 1 valence electron that react vigorously with water to produce flammable hydrogen gas (H₂).

Alkaline Earth Metals

The metallic elements located in Group 2. They are shiny, silvery-white, relatively light, reactive metals with 2 valence electrons that burn in air to produce bright, colourful flames.

Halogens

The non-metallic elements located in Group 17. They are extremely reactive, toxic non-metals with 7 valence electrons that readily combine with metals to form ionic salts.

Noble Gases

The gaseous non-metallic elements located in Group 18. They are colourless, odourless, extremely stable, and unreactive because their outermost electron shell is completely full.

Metalloids

Elements positioned along the zigzag staircase line separating metals from non-metals that possess intermediate properties of both metals and non-metals (e.g., silicon, germanium).

Bohr-Rutherford Diagram

A visual structural model of an atom showing the protons and neutrons in the center, and electrons orbiting around them in circles.

Valence Electrons

The electrons located in the outermost occupied energy level (shell) of an atom, which dictate the chemical reactivity and bonding behaviour of the element.

Atomic Number (Z)

The total number of protons located within the nucleus of an atom, which uniquely identifies the element and equals the number of electrons in a neutral atom.

Mass Number (A)

The total sum of protons and neutrons present inside the nucleus of an atom (A = protons + neutrons).

Ion

A charged particle that results when an atom gains or loses one or more electrons.

Cation

A positively charged ion formed when a neutral metal atom loses one or more valence electrons, resulting in more protons than electrons.

Anion

A negatively charged ion formed when a neutral non-metal atom gains one or more valence electrons, resulting in more electrons than protons.

Ionic Charge

The net electrical charge on an ion, written with the numerical value followed by the plus or minus sign as a superscript (e.g., Mg²⁺, S²⁻, Na⁺).

Stable Octet

The state of having a completely filled outermost electron energy level (shell/orbit), usually containing 8 valence electrons (or 2 for helium), which confers chemical stability similar to noble gases.

Isoelectronic

Having the exact same total number of electrons and identical electron configuration as another atom or ion (e.g., Na⁺, F⁻, and Ne each possess 10 electrons).

Hyponatremia

A dangerous medical condition caused by abnormally low concentrations of sodium ions (Na⁺) in human blood, often triggered by over-consuming plain water during prolonged exercise.

Monatomic Ion

An ion composed of a single atom that has gained or lost electrons (e.g., K⁺, Cl⁻, O²⁻).

Fluoride (F⁻)

The monatomic negative ion of fluorine that integrates into tooth enamel to strengthen its crystal structure and prevent dental cavities.

Ionic Compound

A chemical compound composed of one or more positive metal ions (cations) and one or more negative non-metal ions (anions) held together by electrostatic forces.

Ionic Bond

The simultaneous, strong electrostatic attraction between oppositely charged positive metal ions and negative non-metal ions.

Crystal Lattice

A rigid, highly ordered 3D array of alternating positive and negative ions held together by ionic bonds in a fixed ratio.

Electrolyte

An ionic substance/compound that dissolves in water to produce free-moving ions capable of conducting an electric current and maintaining fluid balance in biological tissues.

Dissociation (Dissolving Process)

The separation of an ionic crystal into individual hydrated ions when placed in a polar solvent like water.