Periodic Table, Properties and Variations

Periodic Table

A systematic arrangement of elements in order of their atomic number, grouped by similar properties.

Atomic Number

The number of protons in the nucleus of an atom, which defines the element.

Periodic Law

The physical and chemical properties of elements are periodic functions of their atomic numbers.

Group

A vertical column in the periodic table, indicating elements with similar chemical properties.

Period

A horizontal row in the periodic table, indicating elements with the same number of electron shells.

Mendeleev

The chemist who created the first widely recognized periodic table based on atomic masses.

Mosely

The scientist who discovered the concept of atomic number, leading to the modern periodic table.

Triad

A group of three elements with similar properties, where the atomic weight of the middle element is the average of the others.

Alkali Metals

Group 1 elements in the periodic table, characterized by their metallic properties and reactivity.

Alkaline Earth Metals

Group 2 elements in the periodic table, known for being less reactive than alkali metals.

Transition Elements

Elements found in groups 3-12, characterized by the filling of d-orbitals.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Metallic Character

The tendency of an element to lose electrons and form positive ions.

Non-Metallic Character

The tendency of an element to gain electrons and form negative ions.

Electronegativity

The tendency of an atom to attract a bonding pair of electrons.

Ionization Energy

The energy required to remove an electron from a neutral atom in the gas phase.

Electron Affinity

The energy change that occurs when an electron is added to a neutral atom.

Periodic Properties

Properties of elements that display a regular pattern when arranged by atomic number.

Acid

A substance that produces hydronium ions (H3O+) when dissolved in water.

Base

A substance that produces hydroxide ions (OH-) in an aqueous solution.

Salt

A compound formed from the neutralization reaction of an acid and a base.

Hydroxyl Group

A functional group consisting of an oxygen atom bonded to a hydrogen atom (-OH).

Ammonia

A compound of nitrogen and hydrogen (NH3), often used as a fertilizer.

Hydrochloric Acid

A strong acid (HCl) that dissociates completely in aqueous solutions.

Sulfuric Acid

A strong acid with the formula H2SO4; known as the 'King of Chemicals'.

Oxidation

The process of losing electrons or increasing oxidation state.

Reduction

The process of gaining electrons or decreasing oxidation state.

Chemical Bond

The lasting attraction between atoms that enables the formation of chemical compounds.

Covalent Bond

A type of bond formed when atoms share one or more pairs of electrons.

Ionic Bond

A type of bond formed through the electrostatic attraction between oppositely charged ions.

Coordinate Bond

A type of covalent bond where one atom donates both electrons in the shared pair.

Cation Exchange

The process where cations are swapped between a solid and a solution.

Lewis Acid