SCIENCE 2Q reviewer

Chap4&5

Atomic theory

A scientific concept that explains the nature of matter and its behavior.

Atomism

A theory that states that all matter is made up of tiny, indivisible particles called "atoms" or "atomos", which are in constant motion.

Solid Sphere model

Dalton's atomic model that believes atoms of the same element are identical in their properties and cannot be subdivided.

Law of Conservation of Mass

States that in a chemical reaction, the total mass of the reactants is equal to the mass of the products.

Law of Definite Proportions

States that a pure substance is composed of the same elements in the same proportions by mass regardless of the source of the substance.

Law of Multiple Proportions

States that when two elements combine to form more than one compound, the mass of one element that combines with a fixed mass of the other element is always in whole-number ratios.

Plum Pudding model

Thomson's atomic model that suggests the existence of electrons and that the empty space is positively charged.

Nuclear model

Rutherford's atomic model that proposes a positively charged nucleus with electrons orbiting it, and that the atom is mostly empty space.

Planetary model

Bohr's atomic model that states electrons are held in their orbits by electrostatic forces and each electron is confined to a specific orbit.

Quantum Mechanic model

Schrodinger's atomic model that describes the probability of finding electrons within given orbitals, and that electrons move at a high speed creating an electron cloud.

Energy levels/electron shells

Each shell can only accommodate a limited number of electrons and contains sublevels or subshells designated by the letters S, P, D, and F.

Protons

Subatomic particles with a positive charge and a mass of 1.

Neutrons

Subatomic particles with no charge and a mass of 1.

Electrons

Subatomic particles with a negative charge and a mass of 1/2000 or 0.0005.

Atomic Number

The number of protons in an atom, which determines the element's identity.

Atomic Mass

The number of protons and neutrons in an atom, also known as "atomic weight" or "mass number".

Ions

Charged particles that can be positively charged (cation) or negatively charged (anion).

Periodic table

Organizes the elements in a particular way based on their atomic number and properties.

Law of Triads

Dobereiner's law that states the atomic mass of the middle element in a triad is approximately equal to the average mass of the heaviest and lightest elements.

Periods

Horizontal rows on the periodic table that represent the number of orbits in an atom.

Groups

Vertical columns on the periodic table that contain elements with similar properties and the same number of valence electrons.

Valence electrons

Electrons in the outermost energy level of an atom.

Alkali Metals

Group IA elements that are highly reactive and have a silvery appearance.

Alkaline Earth Metals

Group IIA elements that are harder, denser, and less reactive than alkali metals.

Halogens

Group VIIA elements that are the most reactive nonmetals and form compounds with most metals.

Noble Gas

Group VIIIA elements that do not react with other elements and are chemically inert.

Metals

Generally hard, lustrous, good conductors of electricity and heat, and can be malleable and ductile.

Nonmetals

Generally exist as gases or solids, brittle, and neither malleable nor ductile.

Metalloids

Elements that possess properties of both metals and nonmetals, and can conduct a limited amount of electricity.

Atomic Diagram

A visual representation of an atom, showing the arrangement of protons, neutrons, and electrons.