chemistry final objectives test 1 weeks 1 to 5

Element

Pure substance consisting of one type of atom

Compound

Substance formed from two or more different elements chemically bonded

Atom

Basic unit of matter and smallest unit of an element

Molecule

Group of two or more atoms held together by chemical bonds

Atomic Number

Number of protons in an atom's nucleus

Mass Number

Total number of protons and neutrons in an atom's nucleus

Isotopes

Atoms of the same element with the same atomic number but different mass numbers due to varying neutron counts

Nucleus

Small dense central core containing protons and neutrons

Electron Cloud/Shells

Region surrounding the nucleus where electrons orbit

Proton Location and Properties

Nucleus with relative mass of 1 and relative charge of +1

Neutron Location and Properties

Nucleus with relative mass of 1 and relative charge of 0

Electron Location and Properties

Electron shells with relative mass of approximately 1/1840 and relative charge of -1

Isotopes Definition and Notation

Variants of a chemical element with different numbers of neutrons represented using mass notation like Carbon-12 or C-12

Valence Shell

Outermost electron shell of an atom

Valence Electron

Electron located in the outermost shell that determines chemical reactivity and group placement

Periodic Table Arrangement

Elements organized sequentially by increasing atomic number with metals on the left/center and non-metals on the upper right

Alkali Metals

Group 1 elements with 1 valence electron that are highly reactive

Alkaline Earth Metals

Group 2 elements with 2 valence electrons

Transition Metals

D-block elements located in Groups 3 through 12

Halogens

Group 17 elements with 7 valence electrons

Noble Gases

Group 18 elements with full valence shells that are chemically inert

Valence Electrons and Group Number

Number of valence electrons corresponds to the main group number of the element

Electron Shells and Period Number

Number of occupied electron shells equals the period number of the element

Group Similarities

Elements in the same group have identical valence electron counts causing similar chemical properties

Metallic Bond Formation

Electrostatic attraction between positive metal cations and a sea of delocalized electrons

Physical Properties of Metals

High melting points due to strong metallic bonds malleable and ductile due to non-directional bonds and conductive in solid and liquid states due to mobile delocalized electrons

Ion Definition and Purpose

Charged atom or group of atoms formed when atoms gain or lose electrons to achieve a full valence shell

Polyatomic and Monatomic Ions

Identified by their valence charges where metals form positive cations and non-metals form negative anions

Ionic Bond Formation and Structure

Transfer of electrons from metal to non-metal forming a 3D giant ionic lattice of alternating ions

Physical Properties of Ionic Compounds

High melting/boiling points non-conductive as solids but conductive when liquid or aqueous due to mobile ions

Covalent Bond Formation

Electrostatic attraction resulting from the sharing of electron pairs between non-metal atoms

Physical Properties of Covalent Molecular Substances

Low melting/boiling points due to weak intermolecular forces and non-conductive in all states due to absence of mobile charged particles

Common Covalent Formulas

Ammonia (NH3) Water (H2O) Hydrogen Peroxide (H2O2) Hydrogen Sulfide (H2S) Chlorine gas (Cl2) Nitrogen gas (N2) Hydrogen gas (H2) Oxygen gas (O2) Fluorine gas (F2) Bromine (Br2) Iodine (I2