unit 3 Flashcards
Nucleon
A particle that exists in the nucleus (protons and neutrons.)
Nuclear charge
The net positive charge of the nucleus, equal to the number of protons in the nucleus.
Ion
A charged atom or group of atoms formed by the gain or loss of
electrons. Protons and electrons are a different number.
Anion vs Cation
A negatively charged ion vs A positively charged ion
Emission Spectrum
the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The frequencies can be used to determine the identity of an element.
Excited State vs. Ground State
A condition where and atom’s electrons occupy higher energy levels than
they normally would due to absorption of energy vs A condition where an atom’s electrons are occupying the lowest possible
energy states
Orbital Notation
Also called “box diagrams”, these schematics describe the location and
spin of every electron in an atom
Photon
An infinitesimally small particle that travels in a wave-fashion that is released when electrons fall from the excited state into the ground state.
It is also known as a packet of light-energy or quanta
Planck’s Constant (h)
A proportionality constant that converts Hz (frequency) to J (energy). It is
6.63 X 10-34 J . sec
Quantum Numbers
A four-digit series of numbers that identifies the location of a specific
electron around the nucleus based on PEL, sublevel, orbital and spin.
Sublevel
Regions of space that electrons occupy making up a principal energy level. Number of orbitals will determine sublevel type
Stable octet
An electron configuration that is reached when atoms gain, lose or share
electrons in an attempt to get a noble gas electron configuration of eight valence electrons. Helium is an exception to this “Rule of Eight”.
Wavelength (λ)
The distance from one peak to the next in a wave. Measured in nanometers.
Frequency
The number of wavelengths that pass a fixed point per second.
Democritus
thought atoms were small hard spheres, infinite in number, and called them Atomos(uncuttable).
Aristotle
Opposed Democritus’ model and thought everything was made out of four elements (earth, water, fire, air). He thought atoms were wrong because they were uncuttable (even by gods), and that opposed the idea that gods could do anything. His theories were more accepted.
John Dalton
Revived Democritus’ ideas, and had the same model, but his theory was what counted (Dalton’s atomic theory).
Dalton’s Atomic Theory
All matter is made of tiny invisible particles called atoms
atoms of the same element are identical
different atoms combine in whole # ratios to form new compounds
Chemical reactions involve the REARRANGEMENT of atoms
Joseph John Thompson
discovered the first subatomic particle, the electron, while studying cathode rays. His magnet both attracted while negative and pushed away while positive, meaning that there must be smaller particles that attract and repel. Also discovered that the electron was 2000x smaller than atom
Ernie Rutherford
was a student of Thompson, and wanted to expand on his theories. Used the gold foil experiment to find out that most of an atom was empty space, but w/ a small & hard nucleus (w/ a positive charge).
Gold foil experiment
Rutherford’s experiment that proved the existence of the nuclear atom He shot positive alpha particles at gold foil, with most passing through. He proved: 1. existence of the nucleus 2. The positive charge of the nucleus 3. The atom is mostly empty space
Neils Bohr Model
used light and photon experiments, and found that electrons moved around the nucleus in fixed PELs.
Erwin Schrodinger
Realized that Bohr’s model was slightly incorrect, as the exact place of electrons can’t be measured, but have areas of high probability called ORBITALS/probability clouds. They appear in the wave particle/quantum mechanical model/electron cloud model, and have different energy levels.
Valence electrons
electrons in the outermost PEL’s S/P sublevels
