Chapter 2 Vocabulary

Experiments by Thomson

-Thomson found that cathode rays were attracted toward the positive electrode of an external electric field -Thomson found that cathode rays were deflected away from the negative end of an external magnetic field

atomic mass

-atomic mass is found on the periodic table for each element -the units used for atomic masses are amu

Bohr's theory of an atom

-electrons only occupy allowed energy levels -energy differences between levels can be calculated from the wavelength of light emitted

speed of light

3.0 x 10^8 m/s

nucleus

a small, dense, positively charged region in the center of an atom

electron

a subatomic particle that has a negative charge

proton

a subatomic particle that has a positive charge and that is found in the nucleus of an atom

neutron

a subatomic particle that has no charge and that is found in the nucleus of an atom

isotopes

atoms of the same element having different masses because they contain different numbers of neutrons

Dalton's atomic theory stated that all matter consist of tiny particles ___. When these tiny particles of different elements combine in simple whole-number ratios, they form ___.

atoms, compounds

from Geiger's experiments, Rutherford concluded that the atom contains a small, extremely dense region in which most of the atom's ___ is concentrated. He called this central region the ___ of the atom.

electrons, mass

what does it mean for energy to be quantized?

energy can have certain values but cannot have amounts between those values

energy levels

energy can have certain values but cannot have amounts between those values (quantization of energy)

atomic number

equal to the number of protons in the atom

mass number

equal to the sum of the number of protons

electromagnetic radiation

light

The modern __ law states that the physical and chemical properties of the elements display a certain periodicity related to their atomic ___.

periodic, number

An atomic orbital represents the ___ of finding a(n) ___ in a region of space.

probability, electron

wavelength

the distance between identical points on two successive waves

periodic law

the elements if arrange according to their atomic weights (masses), show a distinct periodicity (regular variations) of their properties

Dalton's Theory

the first experimentalist based theory of atomic structure

atomic orbital

the probability of finding an electron in a region of space within the principal energy level

atom

the smallest unit an element that retains the chemical properties of that element

atomic mass

the weighted average of the masses of each isotope that makes up the element

excited state

when the electron absorbs energy and is promoted to a higher state

ground state

when the electron of the atom are in the lowest possible energy levels

relaxation

when the electron spontaneously emits energy in the form of a photon of light of the exact energy necessary to return to the ground state