The Periodic Table and Periodic Law

Actinides

A series of 15 metallic elements on the Periodic Table, from Actinium (Ac, 89) to Lawrencium (Lr, 103), known for being radioactive and mainly synthetically created.

Alkali Metals

Highly reactive elements in Group 1 of the periodic table, including lithium, sodium, and potassium, characterized by a single valence electron.

Aluminum

A silvery-white, soft, nonmagnetic metal with atomic number 13, known for its low density and high strength-to-weight ratio, commonly used in various everyday items.

Anions

Negatively charged ions formed when atoms gain electrons, which can affect the chemical properties of substances and form ionic bonds with cations.

Valence Electrons

The outermost electrons of an atom that determine its chemical reactivity and bonding, involved in forming chemical bonds to achieve stability.

Atomic Radius

The size of an atom from the center of its nucleus to its outermost electron orbital, which decreases across a period and increases down a group.

Bromine

A red-brown, corrosive liquid and member of the halogen group, known for its high reactivity and use in flame retardants and various compounds.

Cations

Positively charged ions formed when an atom loses electrons, typically smaller than the parent atom and crucial in chemical reactions.

Diatomic Elements

Elements composed of two identical atoms bonded together, such as H2 and O2, important in understanding chemical reactions.

Dmitri Mendeleev

A Russian scientist known for creating the periodic table, organizing elements by atomic mass and predicting properties of undiscovered elements.

Electronegativity

The tendency of an atom to attract electrons in a chemical bond, increasing across a period and decreasing down a group.

Group 1

Highly reactive alkali metals with one valence electron, including lithium, sodium, and potassium, known for their vigorous reactions with water.

Group 2

Alkaline earth metals with two valence electrons, including beryllium and magnesium, less reactive than Group 1 metals.

Group 7

Halogens, highly reactive nonmetals with seven valence electrons, including fluorine and chlorine, known for forming diatomic molecules.

Group 8

Noble gases with full outer electron shells, making them chemically stable and nonreactive, including helium and neon.

Henry Mosley

A British physicist who developed the concept of atomic numbers, leading to the modern organization of the periodic table.

Hydrogen

The lightest and most abundant element in the universe, a colorless gas used in various chemical processes, including ammonia production.

Ionic Radius

The size of ions, which varies based on the gain or loss of electrons, influencing the properties of ionic compounds.

Ionization Energy

The energy required to remove an electron from a gaseous atom or ion, generally increasing across a period and decreasing down a group.

Lanthanides

A group of 15 metallic elements from atomic numbers 57 to 71, known for their similar chemical behavior and use in electronic devices.

Metals

Malleable, ductile, and conductive materials found on the left side of the periodic table, typically forming positive ions by losing electrons.

Nonmetals

Elements that lack metallic properties, often gaining electrons during reactions, with high ionization energies and electronegativities.

Periodic Law

The concept that elements arranged by atomic number show repeating properties, fundamental in the study of atomic structure.

Reactivity

The tendency of an element or compound to undergo a chemical reaction, influenced by electron configuration and conditions.

Transition Metals

Elements in the middle of the periodic table known for forming multiple oxidation states and exhibiting colorful compounds.

Valence Electrons

The outermost electrons of an atom that play a key role in determining its chemical reactivity and bonding.