How can we help?

You can also find more resources in our Help Center.

43 terms

Unit 3: Atomic Structure, Elements, and the Periodic Table

STUDY
PLAY
Atom
the smallest unit of an element that maintains the properties of that element
Democritus's Atomic Theory
believed that movements of atoms caused the changes in matter
John Dalton's Atomic Theory
All Atoms of a given element were exactly alike. Atoms of different elements could join to form compounds.
J J Thomson's Plum Pudding Model of the Atom
each atom was a sphere filled with a positively charged fluid. The fluid was called the "pudding." Scattered in this fluid were electrons known as the "plums."
Ernest Rutherford's Nuclear Model of the Atom
the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space.
Bohr's Model of the Atom
Placed electrons in planet-like orbits around the nucleus of the atom.
Quantum Model of the Atom
an atomic model in which electrons are treated as waves; also called the wave mechanical model of the atom
Nucleus
an atom's central region, which is made up of protons and neutrons
Proton
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
Electron
a subatomic particle that has a negative electric charge
Energy level
the energy state of an atom
Orbital
a region in an atom where there is a high probability of finding electrons
Valence electron
an electron that is found in the outermost shell of an atom and that determines the atom's chemical properties
Ion
an atom, radical, or molecule that has gained or lot one or more electrons and has a negative or positive charge
Cation
an ion that has a positive charge
Anion
an ion that has a negative charge
Periodic Table of the Elements
A chart of the chemical elements, arranged in three rows, corresponding to the number of electron shells in their atoms
Periodic law
the law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements
Dmitri Mendeleev
Russian chemist who developed a periodic table of the chemical elements and predicted the discovery of several new elements (1834-1907)
Octet
group of eight
Periods or series
a horizontal row of elements in the periodic table
Groups or families
the vertical columns of the periodic table
Atomic number (Z)
the number of protons in the nucleus of an atom
Mass number (A)
the sum of the numbers of protons and neutrons in the nucleus
Isotope
an atom that has the same number of protons as other atoms of the same element do but that has a different number of neutrons
Atomic mass unit (amu)
a unit of mass that describes the mass of an atom or molecule
Avg. atomic mass
the weighted average of the masses of all naturally occurring isotopes of an element
Metal
an element that is shiny and that conducts heat and electricity well
Metalloid
an element that has some characteristics of metals and some characteristics of nonmetals
Nonmetal
an element that conducts heat and electricity poorly and that does not form positive ions in an electrolytic soloution
Semiconductor
an element or compound that conducts electric current better than an insulator but not as well as a conductor
Alkali metals
one of the elements of Group 1 of the periodic table (lithium, sodium, potassium, rubidium, cesium, and francium)
Alkaline Earth metals
one of the elements of Group 2 of the periodic table (beryllium, magnesium, calcium, strontium, barium, and radium)
Transition metals
one of the metals that can use the inner shell before using the outer shell to bond
Halogens
one of the elements of Group 17 of the periodic table (fluorine, chlorine, bromine, iodine, and astatine); halogens combine with most metals to form salts
Noble gases
an non-reactive element of Group 18 of the periodic table (helium, neon, argon, krypton, xenon, or radon) that has eight electrons in its outer level (except for helium, which has two electrons)
Lanthanides
Shiny, reactive metals found in Period 6 from #57-71. Some of these elements are used to make steel and one is found in computer screens to show color.
Actinides
in the 2nd row of transition metals, radioactive, unstable, do not occur in nature
synthetic elements
Elements which do not occur naturally and are made in laboratories.
mole
the SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in 12g of carbon-12
Avogadro's constant
equals 6.02 x 10(twenty-third power); the number of particles in 1 mol
Molar mass
the mass in grams of 1 mol of a substance