Chem. Unit 3 vocab

Mendeleev

organized the elements by increasing atomic mass and so that elements in the same row have similar properties

Moseley

rearranged the elements by increasing atomic number

Periodic Law

“when elements are arranged in order of increasing atomic numbers, there is a periodic pattern in their physical and chemical properties”

Period

the horizontal rows of the periodic table

Group

the vertical columns on periodic table

S block

representative elements

P block

representative elements

D block

transition metals

F block

inner transition metals

Alkali Metals

elements that make up group 1 of the periodic table, excluding hydrogen

Alkaline Earth Metals

elements in Group 2 of the periodic table

Transition Metals

elements located in the middle of the periodic table, spanning Groups 3 through 12 (the d-block)

Halogens

elements in Group 17

Noble Gases

elements that make up Group 18

Metals

a chemical element that easily loses electrons to form positive ions (cations)

Non metals

elements on the upper-right side of the periodic table

Metalloids

touch the staircase and have properties of both metals and non-metals (Al is a metal)

Electron Configuration

the distribution of an atom's or molecule's electrons among atomic or molecular orbitals

Principal Energy Levels

a main region or floor around an atom's nucleus where electrons reside

Sublevels

correspond to the different areas an electron can be located on an atom

Atomic Orbitals

each sublevel is oriented differently in 3-D space, and each orientation is called an atomic orbital

Aufbau Principle

electrons enter sublevels with the lowest energy first

Orbital Notation

uses circles to represent atomic orbitals with a label underneath to indicate sublevel and energy level

Pauli Principle

atomic orbitals can hold only 2 electrons at most and they must have opposite spins

Hund’s Rule

when electrons fill orbitals with the same energy level, such as the p, d, or f, they occupy each orbital with parallel spins before any pairing occurs

Isoelectronic

two or more atoms, ions, or molecules share the exact same number of electrons and the same electron configuration

Valence Electrons

electrons located in the outermost energy level (responsible for bonding)

Atomic Radius

the distance from the center of an atom's nucleus to the outer boundary of its electron shell

Nuclear Charge

the total positive charge of an atomic nucleus

Shielding Effect

the inner-core electrons block or reduce the attractive pull of the positive nucleus on valence electrons

Ionization Energy

the minimum amount of energy required to remove the outermost electron from an isolated gaseous atom to form a positively charged cation

Ionic Size

the distance from the nucleus of an ion to its outer edge

Electronegativity

an atom's tendency to attract shared electrons toward itself when forming a chemical bond