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