Science
atomic mass unit
-unit of measurement for atomic particles -one-twelfth the mass of a carboun atom containing six protons and six neutrons
chemical symbol
a letter and possibly two stand for an element
elements
abbreviated in scientific shorthand-first letter or two of element's name
isotopes
atoms of the same element with different numbers of neutrons
hydrogen and helium
building blocks of other naturally occurring elements
elements are organized in the periodic table
by increasing atomic number
atomic mass
composed mostly of the protons and neutrons in the nucleus
neutrons
dont have an electrical charge
number of neutrons
equal to mass number minus atomic number
protons
have electrical charge of 1+
electrons
have electrical charge of 1-
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
Henry G.J. Moseley
in 1913 arranged the elements by atomic number rather than atomic mass
Dimitri Medeleev
in the late 1800s evised the first periodic table based on atomic mass
quarks
smaller particles that make up protons and neutrons
atom
smallest piece of matter that still gas the properties of the element
supenovas
spread heavier elements throughout the universe
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
average atomic mass
the weighted-average mass of an element's isotopes
groups or families
vertical columns in the periodic table of elements with similar properties -18 -elements with the same valence number
metal, nonmetals,or metalloids(semimetals)
what elements are classified as