Download Vocabulary Terms - Dayton Independent Schools

Earth and the Universe
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1.
atom
the smallest particle of an element that still
retains the properties of the element
21.
nuclear
fission
process of splitting an atomic nucleus into two
or more nuclei with smaller masses
2.
atomic
number
number of protons in an atom's nucleus
22.
nuclear
fusion
reaction in which two or more atomic nuclei
form a nucleus with a larger mass
3.
average
atomic
mass
weighted-average mass of mixture of an
element's isotopes
23.
nucleus
positively charged center of an atom that
contains protons and neutrons and is
surrounded by a cloud of electrons
4.
big bang
theory
the theory that the universe started with a big
bang, or explosion, and has been expanding
ever since
24.
period
horizontal row in the periodic table
25.
periodic
table
5.
cosmology
study of how the universe began, what it is
made of, and how it continues to evolve
organized list of all known elements that are
arranged by increasing atomic number and
by changes in chemical and physical
properties
6.
dark energy
energy that might be causing accelerated
expansion of the universe
26.
photon
7.
dark matter
unseen mass that adds to the gravity of a
galaxy, but cannot be detected or seen
particle that electromagnetic waves sometimes
behave like; has energy that increases as the
frequency of the electromagnetic wave
increases
8.
electron
particle surrounding the center of an atom that
has a charge of 1-
27.
photosphere
light-emitting surface of the Sun
28.
proton
particle, composed of quarks, inside the
nucleus of an atom that has a charge of 1+
29.
quarks
particles of matter that make up protons and
neutrons
30.
white dwarf
giant star that has lost its outer layers, leaving
behind a hot, dense core that continues to
contract under gravity
electron
cloud
area around the nucleus of an atom where the
atom's electrons are most likely to be found
electron
dot diagram
uses the symbol for an element and dots
representing the number of electrons in the
element's outer energy level
11.
galaxy
large group of stars, gas, and dust held
together by gravity; most commonly can be
elliptical, spiral, and irregular
12.
giant
late stage in a star's life cycle that occurs when
its hydrogen fuel is depleted, its core contracts,
and its outer layers expand and cool
13.
group
vertical column in the periodic table
14.
heliocentric
model
Sun-centered model of the solar system
15.
isotope
atoms of the same element that have different
numbers of neutrons
16.
light-year
distance light travels in one year - about 9.5
trillion km
17.
main
sequence
section of an H-R diagram that is plotted from
the upper left to the lower right and contains
90 percent of all known stars
18.
mass
number
sum of the number of protons and neutrons in
an atom's nucleus
19.
Milky Way
our spiral-shaped galaxy, which contains the
solar system and about 400 billion stars,
including the Sun, and measures about
100,000 light-years across
20.
neutron
neutral particle, composed of quarks, inside
the nucleus of an atom
9.
10.