How can we help?

You can also find more resources in our Help Center.

19 terms

Chemistry 521A - Chapter 4

STUDY
PLAY
atom
the smallest particle of an element that retains its identity in a chemical reaction
Dalton's atomic theory
the first theory to releate chemical changes to events at the atomic level; described the structure and chemical reactivity of matter in terms of atoms
Democritus
Greek philosopher who was among the first to suggest the existence of atoms
Scanning Tunneling microscope
an instrument used to generate images of individual atoms
electrons
negatively charged subatomic particles
cathode ray
stream of electons produced at the negative electrode of a tube containing a gas at low pressure
protons
positively charged subatomic particles
neutrons
subatomic particles with no charge
nucleus
the central core of the atom which is made up of protons and neutrons
atomic number
the number of protons in the nucleus of an atom of an element
mass number
the total numbe rof protons and neutrons in the nucleus of an atom
isotopes
atoms of the same element have the same atomic number of different atomic masses due to a different number of neutrons
atomic mass unit (amu)
a unit of mass equal to one-twelfth the mass of a carbon-12 atom
atomic mass
the weighted average of the masses of the isotopes of an element
periodic table
an arrangement of elements in which the elemtns are separated into groups based on a set of repeating properties
period
a horizontal row of elements in the periodic table
group
a vertical column of elements in the periodic table; the constiuent elements of a group have similar chemical and physical properties
Atomic number
a number equal to the number of protons as well as the number of electrons in an atom
Number of neutrons
Equal to the mass number minus the atomic number