Unit 3: Atoms Flashcards
the smallest unit of an element
Atom
scientist who composed and published his Atomic Theory in 1808
John Dalton
What are the 2 changes made to the Atomic Theory since it was published by Dalton?
- There are isotopes of elements which do have a different mass.
- Atoms can be split to form atomic bombs.
What did Crookes do?
Crookes determined that negative particles of some kind exist using the Cathode Ray Tube.
Relating to: Electrons
What did J.J. Thomson do?
Thomson determined that electrons must be negatively charged using the Cathode Ray Deflection and bar magnet. He also named the negative particles electrons.
Relating to: Electrons, charge, name
What did Robert Milikan do?
Milikan determined that electrons are lighter than protons and neutrons using the Oil Drop Experiment.
Relating to: Electron weight
What did Ernest Rutherford, Marsden, and Hans Geiger do?
The determined: 1. The nucleus is very small. 2. The nucleus is positively charged. using the Gold Foil Experiment. Relating to: The nucleus of the atom and the proton
What is the weight of a proton?
1.007 amu
What is the weight of a neutron?
1.0087 amu
What is the weight of an electron?
5.486 x 10^-4 amu
What contains positive protons and neutral neutrons?
The nucleus
What contains negative electrons?
The energy levels
the number of protons in an atom. This is ALWAYS a whole number. You can determine the # of electrons from this for a neutral atom because the # of protons= the # of electrons
Atomic Number
sum of protons and neutrons. This is ALWAYS a whole number. This number is the ROUNDED atomic weight (atomic mass) of an element.
Mass Number
a different form of an element that contains a different number of neutrons but has the same atomic number (number of protons).
Isotopes
the decimal number on the periodic table for that element. This is obtained by getting the weighted average of all forms of that element known to man.
Average Atomic Mass
the weight of the element measured in grams
Atomic weight
a unit used to measure atoms or molecules (created by Amedeo Avogadro)
Mole
a form of energy that travels through space as waves at the speed of light, 3.00 x 10^8 m/s.
Electromagnetic Radiation
the distance from crest to crest or trough to trough of a wave
Wavelength
the number of waves that pass a given point in one second
Frequency
symbol used to represent wavelength. Wavelength is expressed in units of nanometers for visible light.
lambda
unit used to measure frequency
Hertz, Hz
As wavelength increases, frequency and energy
decreases
As wavelength decreases, frequency and energy
increases
What pigment transmits the wavelengths corresponding to the color red in the visible light portion of the electromagnetic spectrum?
A red pigment
What color reflects all wavelengths of color?
White
What color absorbs all wavelengths of color?
Black
A black light contains wavelengths in which spectrum along with some in the far left violet range. These wavelengths cause some pigments to fluoresce.
UV
units of light energy. Photosynthesis is a chemical process that occurs in nature when sunlight strikes the chlorophyll in plants, converting it to energy.
Photons
Who suggested that electrons were particles?
Niels Bohr
Who suggested that electrons have wave-like characteristics?
DeBroglie
Who developed DeBroglie’s idea and solved wave equations to make predictions about the location of electrons in an atom?
Schrodinger
The nucleus contains protons and neutrons surrounded by electrons in fixed orbits. The electrons also have a fixed energy. This concept was used to develop current models of the atom but doesn’t explain electron behavior now.
Bohr’s Model
most stable state of an element
the ground state
when the electrons are energized, move out of their normal energy levels, return to that level, and in the process give off light, heat, and/or energy.
the excited state
A regular atom is referred to as a
nucleon
Nucleons are represented as a fraction with the ________ over the atomic number to the left of the symbol.
mass number
the spontaneous decay of certain atoms with the release of energy in the form of alpha, beta, and gamma particles. Radiation comes from the nucleus of an atom.
Radioactive decay
What is the nature of an alpha particle?
a helium nucleus
What is the nature of a beta particle?
an electron
What is the nature of a gamma particle?
High energy and high electromagnetic radiation
What is the charge of an alpha particle?
+2
What is the charge of a beta particle?
-1
What is the charge of a gamma particle?
0
What is the mass of an alpha particle?
4
What is the mass of a beta particle?
1/1840
What is the mass of a gamma particle?
0
What can an alpha particle be stopped by?
clothing, paper
What can a beta particle be stopped by?
Aluminum foil and plastic
What can a gamma particle be stopped by?
lead
the spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by emission of particles, electromagnetic radiation, or both.
Nuclear decay
the energy that is emitted when a nuclide undergoes decay
Radiation
What are the 2 characteristics of stable nuclei?
- Approximate 1:1 proton-neutron ratio
2. Tend to have even numbers of nucleons (protons + neutrons)
If an atom has an atomic number above ___, no stable nuclide exists due to repulsive forces of the protons.
82
a reaction in which the nucleus is affected by a loss of energy in the form of alpha particles, beta particles, or gamma rays.
nuclear reaction
the loss of these particles (alpha and beta) particles change the atomic number and mass number of the element, changing the identity. This is called _________.
Transmutation
the amount of time it takes for your beginning amount of material to halve itself. If you halve the amount of material you have each time, it never runs out.
Half-life
Bombarding a nucleus with ______ particles can produce new, artificial elements.
Alpha
Who used a hydrogen ion which has less charge, less repulsion. Neutrons as bombarding particles have no repulsion from the positive nucleus. (1932)
Crockoft and Walton
When was the use of accelerated heavier nuclei?
1970
the process of heavy nuclei capturing neutrons, splitting to form other smaller nuclei and releasing more neutrons. Large amount of energy can be released and if this release is not controlled, a chain reaction can occur.
Nuclear Fission
the combining of smaller nuclei into larger ones with the release of energy. This is harder to perform than a fission reaction. It occurs on the sun. Hydrogen atoms are used to fuse into helium atoms.
Nuclear Fusion
