Unit Two – Atomic Structure, Periodic Table, & Nuclear Chemistry

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Atom number
Number of protons in the nucleus of an atom
Atomic mass
Number of protons and neutrons
Smallest particle of an element
chemical symbol
A one or two letter representation of an element
A subatomic particle that has a negative charge; smallest of subatomic particles
A class of elements characterized by physical properties that include shininess, malleability, ductility, and conductivity.
alkali metals
has one valence electron; highly reactive; found in the first column of the periodic table
A nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy.
alpha particle
A cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivity
electron cloud
a region around the nucleus of an atom where electrons are likely to be found
A pure substance made of only one kind of atom
energy level
A particular region where electrons can “orbit” a nucleus.
An atom or group of atoms that has a positive or negative charge.
A horizontal row of elements in the periodic table
Element that is usually a gas or brittle solid at room temperature; poor conductor of heat and electricity; tends to form anion
alkali earth metal
an element with 2 valence electrons, harder, higher melting point, and denser than alkali metals. Reactive, but less than corresponding alkali metal
combining of small nuclei into larger ones, releasing energy
beta particle
an electron emitted from the nucleus during some kinds of radioactive decay
Atoms of the same element that have different numbers of neutrons
law of charges
like charges repel, opposite charges attract
Lewis dot diagram
A method for representing an atom’s valence electrons using dots around the element symbol.
The largest subatomic particle; no charge; found in the nucleus of an atom
Group of element in the same column of the periodic table; they are similar chemical properties
Elements along the staircase. Have properties of both metals and nonmetals. Ex: Silicon
Contains nonmetals, 7 valence electrons in it’s outermost energy level. Very reactive
gamma rays
Energy (electromagnetic) waves given off during radioactive decay, fission, or fusion
The time required for one half of the atoms of a radioisotope to emit radiation or decay products
A region that is located at the center of an atom and contains most of the atom’s mass (protons and neutrons)
A subatomic particle that has a positive charge and that is found in the nucleus of an atom
Periodic Law
the law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements
valence electron
Electrons in the outermost energy level of an atom
A column on the periodic table
noble gases
Family or group of elements with the complete outer electron levels; nonreactive or inert gases
radioactive decay
the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element
radioactive radiation
energy during radioactive decay, fission, or fusion
Octet Rule
States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons
Categories: Nuclear Chemistry