How can we help?

You can also find more resources in our Help Center.

21 terms

Chap 4&5 Test

STUDY
PLAY
Atom
The smallest particle of an element that retains its identity in a chemical reaction
scanning tunneling microscope
an instrument used to generate images of individual atoms
John Dalton
english chemist and schoolteacher who formulated a theory to describe 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
Electrons
negatively charged particles found outside the nucleus
Cathode ray
a stream of electrons produced at the negative electrode (cathode) of a tube containing a gas at low pressure
Protons
positively charged particles located in the nucleus
Neutrons
subatomic particles with no charge
nucleus
the center of the atom which contains the protons and neutrons
atomic number
the number of protons in the nucleus of an atom
periodic table
an arrangement of elements according to similarities in their properties
mass number
the sum of the numbers of protons and neutrons in the nucleus of an atom
group
a vertical column of elements in the periodic table
isotopes
atoms with the same number of protons but different numbers of neutrons
atomic mass unit (amu)
1/12th of the mass of a carbon 12 atom
atomic mass
weighted average mass of the atoms in a naturally occurring sample of an element
period
a horizontal row of the periodic table
quantum
the amount of energy needed to move an electron from one energy level to another
atomic orbitals
a region in space around the nucleus of an atoms where an electron is likely to be moving
energy level
the regions around the nucleus within which the electrons have the highest probability of being found
quantum mechanical model
the modern description of the behavior of electrons in atoms