elements
abbreviated in scientific shorthand-first letter or two of element's name
chemical symbol
a letter and possibly two stand for an element
atom
smallest piece of matter that still gas the properties of the element
protons
have electrical charge of 1+
neutrons
dont have an electrical charge
electrons
have electrical charge of 1-
quarks
smaller particles that make up protons and neutrons
atomic mass
composed mostly of the protons and neutrons in the nucleus
atomic mass unit
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atomic number
the number of protons in an atom; number of protons also identifies the element
-this number tells exactly what the element or atom is. It connot be changed or it will be antother element
mass number
the sum of the number of protons and neutrons in the nucleus of an atom
isotopes
atoms of the same element with different numbers of neutrons
number of neutrons
equal to mass number minus atomic number
average atomic mass
the weighted-average mass of an element's isotopes
elements are organized in the periodic table
by increasing atomic number
Dimitri Medeleev
in the late 1800s evised the first periodic table based on atomic mass
Henry G.J. Moseley
in 1913 arranged the elements by atomic number rather than atomic mass
groups or families
vertical columns in the periodic table of elements with similar properties
-18
-elements with the same valence number
periods
horizontal rows of wlwments that contain increasing numbers of protons and electrons
-twll us the number of energy levels or shells and the number of electrons on each energy level for every element on that row
metal, nonmetals,or metalloids(semimetals)
what elements are classified as
hydrogen and helium
building blocks of other naturally occurring elements
supenovas
spread heavier elements throughout the universe