period table

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Alchemy

Ancient study combining chemistry, mysticism, and philosophy.

Robert Boyle

Identified pure substances; refuted Aristotle's four elements.

Antoine Lavoisier

Broke down water into hydrogen and oxygen.

Jons Jakob Berzelius

Developed symbolic system for chemical elements.

Chemical Symbols

Represent elements; often derived from Latin names.

Monatomic Elements

Elements existing as single atoms, e.g., helium.

Diatomic Elements

Molecules of two identical atoms, e.g., hydrogen.

Polyatomic Molecules

Molecules containing more than two atoms.

Johann Dobereiner

Grouped elements into triads based on properties.

A. E. Beguyer de Chancourtois

Graphically organized elements by atomic mass.

John Newlands

Proposed the law of octaves in element properties.

Dmitri Mendeleev

Created periodic table with spaces for undiscovered elements.

Periodic Law

Properties vary periodically with atomic mass.

Henry Moseley

Revised periodic table by atomic number, not mass.

Metals

Three-quarters of elements; good conductors, malleable.

Nonmetals

Exist as solids, liquids, or gases; poor conductors.

Metalloids

Elements with properties between metals and nonmetals.

Element Families

Columns in periodic table with similar properties.

Alkali Metals

Group 1A; very reactive with one valence electron.

Alkaline-Earth Metals

Group 2A; slightly less reactive with two valence electrons.

Transition Elements

Groups 1B-8B; metals with 1 or 2 valence electrons.

Valence Electrons

Electrons in the outer shell; determine bonding.

Noble Gases

Inert gases; do not readily react with others.

Atomic Number

Number of protons in an atom's nucleus.

Atomic Mass

Weighted average mass of an element's isotopes.

Malleability

Ability to be shaped or rolled into sheets.

Ductility

Ability to be drawn into wires.

Diatomic Molecule

Molecule composed of two atoms, e.g., O2.

Periodic Trends

Patterns in properties across the periodic table.

Atomic Radius

Distance from nucleus to outermost electron shell.

Electronegativity

Ability of an atom to attract electrons.

Electron Dot Notation

Representation of valence electrons using dots.

Group Number

Indicates number of valence electrons in elements.

Energy Levels

Shells around nucleus where electrons reside.

Lewis Dot Structures

Diagrams representing valence electrons for bonding.

Valence Electron Configuration

Arrangement of valence electrons in an atom.

Mass Number

Total number of protons and neutrons in an atom.

Octet Rule

Atoms strive for eight valence electrons for stability.

Isotopes

Atoms of the same element with different neutron counts.

Lewis Dot Structure

Diagram showing valence electrons around an atom.

Most reactive element

Fluorine (F).

Octet rule

Atoms bond to achieve a full outer shell of eight electrons.

Element families

Element families or groups in the periodic table are defined by having the same number of valence electrons.

Valence electrons

Valence electrons are significant because they are involved in chemical bonding.

Periodic table arrangement

The arrangement of elements in the periodic table reflects their properties based on atomic number.

Subatomic particles

Protons define the element's identity and positive charge, neutrons contribute to the mass and stability of the nucleus, and electrons determine chemical behavior.

Atomic radius trend

Atomic radius decreases as you move across a period.

What happens to an atom if it gains electrons?

It becomes negatively charged (anion).

What happens to an atom if it loses electrons?

It becomes positively charged (cation).