science chapter 13 Flashcards
the organized study of the composition and interactions of matter
chemistry
proposed by john dalton, foundation for understanding of matter
atomic theory of matter
tiny particles (greek word meaning “not cuttable”)
atoms
composed of a single type of atom
elements
composed of atoms of two or more elements bonded together
compounds
pioneer of the atomic theory
john dalton
a unique abbreviation given to each element
chemical symbol
atoms are composed of still smaller particles of matter called…
subatomic particles
a dense central core in an atom
nucleus
the two types of nucleons
protons and neutrons
carry a + electric charge
protons
electrically neutral, no electric charge
neutron
the number of protons in the nucleus
atomic number
atoms that are the same element but have different numbers of neutrons
isotopes
protons and neutrons are composed of even smaller particles called…
quarks
carries a - electric charge
electron
each layer that surrounds the nucleus (energy levels)
electron shell
an atom that has an electric charge because of losing or gaining electrons
ion
the total number of protons and neutrons in the nucleus
mass number
the masses of atoms are usually measured in…
atomic mass units (u)
the average mass of all the natural isotopes of an element
average atomic mass
states that tiny particles like electrons do not absorb or release energy in a smooth flow
quantum theory
Niels Bohr, the most familiar model of the atom
bohr model
Schrodinger’s hypothesis, or the quantum-mechanical model, explained some puzzling features of atomic structure
wave-mechanical model
werner heisenberg stated that it is impossible to measure both the position and velocity of an electron with certainty
Heisenberg uncertainty principle
a modified version of the wave-mechanical model
electron-cloud model
can hold up to two electrons, the region where electrons move unpredictably
orbitals
the overall motion of each electron can be mathematically represented by four…
quantum numbers
says that no two electrons in an atom can have the same four quantum numbers
pauli exclusion principle
when an atomic nucleus breaks up or undergoes a change, it gives off energy as…
nuclear radiation
any substance that is unstable (and thus likely to produce radiation)
radioactive
when an atomic nucleus changes from a higher-energy state to a lower-energy state, emitting energy as radiation
radioactive decay
the length of time required for one-half of the original substance to decay into a new substance
half-life
occurs when an unstable atom ejects a clump of two protons and two neutrons to reach a more stable state
alpha decay
the division of a nucleus
nuclear fission
domino effect of neutrons splitting other atoms
chain reaction
the certain amount of fissionable material present
critical mass
a device that initiates an uncontrolled chain reaction
atomic bomb
harnesses a type of controlled chain reaction
nuclear reactor
the process of combining two nuclei to form a heavier nucleus and thereby releasing energy
nuclear fusion
produce more nuclear fuel than they use
breeder reactors
uses nuclear fusion to release a tremendous amount of energy
hydrogen bomb
the electrons in the valence shell
valence electrons
most atoms tend to react to obtain eight electrons in their valence shell
octet rule
states that the elements show regular and repeating, or periodic, properties when they are arranged by their increasing atomic numbers
periodic law
developed by dmitri mendeleev
periodic table of the elements
each row in the table
period
each column
group
elements n groups 1, 2, and 13-18
main-group elements
hard, dense, shiny solids that are good conductors of heat and electricity and have high melting points
metals
poor conductors of heat and electricity
nonmetals
are all solids that have properties intermediate between metals and nonmetals
semimetals
very soft, shiny metals with low melting points; has only one valence electron
alkali metals
has two valence electrons; harder, denser and less reactive than the alkali metals but are still softer and less dense than most metals
alkaline earth metals
groups 3 to 12; either 1 or 2 electrons in their valence shells; are known for their strength and hardness
transition metals
groups 3 to 4; the first 15 are called the lanthanoids, the other 15 are the actinoids; all have 2 electrons in there valence shells and share similiar properties
inner transition metals
a basic constituent of all living things and the second most abundant element in the human body
carbon
group 17; “salt formers”; they easily combine with alkali and alkaline earth metals to form salts
halogens
found in nature in their pure states; no natural compounds of these gases exist
noble gases
