Atomic Structure and the Periodic Table

Atom

Smallest unit of an element

Element

Substance made up of only one type of atom

Proton

Positively charged sub-atomic particle in the nucleus

Neutron

Neutral sub-atomic particle in the nucleus

Nucleus

Central part of an atom containing protons and neutrons

Electron

Negatively charged sub-atomic particle outside the nucleus

Electron Cloud

Region surrounding the nucleus where electrons are found

Shell

Energy level where electrons are organized

Valence Shell

Outermost shell of an atom

Nucleon

Proton or neutron in the nucleus

Sub-atomic Particle

Particle smaller than an atom (proton, neutron, electron)

Isotope

Atoms of the same element with different numbers of neutrons

Allotrope

Different forms of the same element in the same physical state

Atomic Mass

Weighted average mass of an element's isotopes

AMU

Atomic Mass Unit, unit of mass for atoms

Mass Number

Total number of protons and neutrons in an atom

Atomic Number

Number of protons in an atom

Monatomic Element

Element consisting of single atoms

Polyatomic Element

Element consisting of molecules made up of multiple atoms

Average Atomic Mass

Weighted average mass of an element's isotopes

Period

Horizontal row on the periodic table

Group or Family

Vertical column on the periodic table

Metal

Element that is a good conductor of heat and electricity

Nonmetal

Element that is a poor conductor of heat and electricity

Metalloid

Element with properties between metals and nonmetals

Energy Levels

Shells where electrons are organized based on energy

Valence Electrons

Electrons in the outermost shell of an atom

Periodic Table

Arrangement of elements based on atomic number and properties

Atomic Symbol

Abbreviation for an element

Ions

Charged atoms formed by gaining or losing electrons

Column

Vertical group of elements on the periodic table

Valence Electrons

Electrons in the outermost shell of an atom

Bohr Model

Model of the atom with energy levels and valence electrons

Main Group Elements

Elements in the s and p blocks of the periodic table

Transition Metals

Elements in the d block of the periodic table

Noble Gases

Group 18 elements on the periodic table. They have full outer electron shells, making them stable and unreactive. Common examples include helium, neon, argon, krypton, xenon, and radon.

Lanthanides

Elements in the f block of the periodic table

Metalloids

Elements with properties between metals and nonmetals (B, Si, Ge, As, Sb, Te)

Diatomic Elements

Elements that exist as molecules made up of two atoms (H2, N2, O2, F2, Cl2, Br2, I2)

Metals

Elements that are good conductors of heat and electricity

Nonmetals

Elements that are poor conductors of heat and electricity

Metalloids

Elements with properties between metals and nonmetals (B, Si, Ge, As, Sb, Te)

Line Spectra

Patterns of light emitted by excited atoms

Colors

Different wavelengths of light that we perceive

Atomic Line Spectrum

Pattern of specific wavelengths of light emitted by excited atoms

Continuous Spectrum

Unbroken range of colors in a spectrum

Wavelength

Distance between two consecutive peaks or troughs of a wave

Frequency

Number of wave cycles passing a point per second

Energy

Ability to do work or cause change

Electromagnetic Waves

Waves that can travel through empty space

Photon

Particle of light with energy proportional to its frequency

Azimuthal

Quantum number that determines the shape of an orbital

Absorption Spectra

Pattern of specific wavelengths of light absorbed by atoms

Emission Spectra

Pattern of specific wavelengths of light emitted by excited atoms

Bright-line Spectrum

Pattern of specific wavelengths of light emitted by excited atoms

Spin-up

Orientation of an electron's spin in one direction

Spin-down

Orientation of an electron's spin in the opposite direction

Ground-state

Lowest energy state of an atom

Bohr Potential Energy Diagram

Diagram showing the relative energy levels of an atom

Hydrogen

Element with one valence electron

Orbit

Path followed by an electron around the nucleus (Bohr Model)

Orbital

Region of space where an electron is likely to be found (Schrödinger's Model)

Ground-state Orbital Diagram

Diagram showing the arrangement of electrons in an atom's orbitals

Ground-state Electron Configuration

Arrangement of electrons in an atom's energy levels

Aufbau Principle

Electrons fill orbitals in order of increasing energy

Pauli Exclusion Principle

Each orbital can hold a maximum of two electrons with opposite spins

Hund's Rule

Electrons fill orbitals of the same energy with parallel spins before pairing

Quantum Numbers

Numbers used to describe the properties of electrons

Wavelength

Distance between two consecutive peaks or troughs of a wave

Frequency

Number of wave cycles passing a point per second

Amplitude

Height of a wave from the center to a peak or trough

Heisenberg Uncertainty Principle

Inability to know both the position and momentum of a particle simultaneously

Degenerate

Orbitals with the same energy

Azimuthal

Quantum number that determines the shape of an orbital

Core Electrons

Electrons in the inner shells of an atom

Absorption Spectra

Pattern of specific wavelengths of light absorbed by atoms

Emission Spectra

Pattern of specific wavelengths of light emitted by excited atoms

Bright-line Spectrum

Pattern of specific wavelengths of light emitted by excited atoms

Spin-up

Orientation of an electron's spin in one direction

Spin-down

Orientation of an electron's spin in the opposite direction

Ground-state

Lowest energy state of an atom

Bohr Potential Energy Diagram

Diagram showing the relative energy levels of an atom

Hydrogen

Element with one valence electron

Orbit

Path followed by an electron around the nucleus (Bohr Model)

Orbital

Region of space where an electron is likely to be found (Schrödinger's Model)

Ground-state Orbital Diagram

Diagram showing the arrangement of electrons in an atom's orbitals

Ground-state Electron Configuration

Arrangement of electrons in an atom's energy levels

Aufbau Principle

Electrons fill orbitals in order of increasing energy

Pauli Exclusion Principle

Each orbital can hold a maximum of two electrons with opposite spins

Hund's Rule

Electrons fill orbitals of the same energy with parallel spins before pairing

Quantum Numbers

Numbers used to describe the properties of electrons

Actinides

elements in the f block of the periodic table

d-block elements when doing orbital/electron diagrams

(n-1)d

f-block elements when doing orbital/electron diagrams

(n-2)f

alkali metals

Group 1 elements with one valence electron, found in the leftmost column of the periodic table. Highly reactive and easily lose electrons. (not including hydrogen)

alkaline earth metals

Group of metallic elements in the periodic table. They are found in Group 2 and have two valence electrons. They are less reactive than alkali metals but still reactive enough to not be found in nature as free elements. Examples include magnesium, calcium, and barium. They have low melting and boiling points, and are commonly used in various industrial applications.

Pnictogens

Group 15 or 5A elements on the periodic table. They have 5 valence electrons and include nitrogen, phosphorus, arsenic, antimony, and bismuth. They exhibit diverse chemical properties.

Chalcogens

Group 16 or 6A elements in the periodic table. They include oxygen, sulfur, selenium, tellurium, and polonium. Chalcogens have 6 valence electrons and are highly reactive. They can form compounds with metals and nonmetals.

Halogens

Group 17 or 7A elements in the periodic table known for their high reactivity and ability to form salts. They include fluorine, chlorine, bromine, iodine, and astatine. They are non-metals

The 6 metalloids

Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), and Tellurium (Te).