Atom
Smallest particle of an element that retains its identitity in a chemical reaction
Democritus
He believed that atoms were invisible and indestructable
Dalton's Atomic Theory
1. All elements are composed of atoms
2.Atoms of the same element are identical. The atoms of one element are different than those of any other.
3. Atoms of different elements can physically mix together or chemically combine to form compounds
4.Chemical
Subatomic Particles
Electrons, protons, and neutrons
Electrons
Negatively charged subatomic particles
Cathode Ray
Glowing beam that travels from cathode to anode.
Protons
Positively charged subatomic particles
Neutrons
Subatomic particles with no charge but with a mass nearly equal to that of a proton
Nucleus
Tiny central core of an atom and is composed of protons and neutrons
Nucleus
Protons and neutrons are located in the...
Atomic Number
Number of protons in the nucleus
Mass Number
Total number of protons and neutrons in an atom
Number of Neutrons
Mass number-atomic number
Isotopes
Atoms that have the same number of protons but different numbers of neutrons
Atomic Mass Unit
One of 12 atomic mass units
Atomic Mass
Weighted average mass of the atoms in a naturally occuring sample of the element.
Period
Horozontal row of the periodic table
Group
Vertical row of the periodic table
Rutherford
This person's atomic model could not explain the chemical properties of elements.
Bohr
Proposed that an electron is found only in specific circular paths, or orbits, around the nucleus
Energy Levels
The fixed energies an electron can have
Quantum
The amount of energy required to move an electron from one energy level to another.
Quantum mechanical model
The modern description of the electrons in atoms
Atomic Orbital
Region of space in which there is a high probability of finding an electron
Electron Configuration
The ways in which electrons are arranged in various orbitals around the nuclei of atoms
Aufbau Principle
Accoring to this principle, electrons occupy the orbitals of lowest energy first
Pauli Exclusion Principle
According to this principle, an atomic orbial may describe at most two electrons.
Hund's Rule
This states that electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible.
Amplitude
Wave's height from zero to crest
Wavelength
Distance between crests
Frequency
Number of wave cycles to pass a given point per unit of time.
Hertz
SI unit of cycles per second
Electromagnetic radiation
Radio waves, microwaves, infrared rays, visible light, ultraviolet waves, x-rays, and gamma rays
Spectrum
When sunlight passes thrugh a prism, they different frequencies separate into a --- of colors.
Atomic Emission spectrum
The frequencies of light emitted by an element spearate into discrete lines
Ground State
The lowest possible energy of the electron
Photons
Light quanta
Heisenberg
This principle states that it is impossivle to know exactly both the velocity and the position of the particle at the same time.