Chapter 17
unit of measurement for atomic particles
atomic mass unit (amu) which is one twelfth the mass of a carbon atom containing six protons and six neutrons
Elements are organized in the periodic table by
atomic number
Isotopes
atoms of the same element with the different number of neutrons
hydrogen and helium
building blocks for all other elements
energy level one
can hold 2 electrons
Atomic Mass
composed mostly of protons and neutrons
Moseley
created current periodic table in 1913; used atomic number
electron cloud
current model; shows electrons traveling around the nucleus in their energy levels
Same elements exist
everywhere in the universe
supernovas
exploding star; responsible for ejecting heavier elements throughout the universe
solid sphere
first model; created by Dalton
proton
have a charge of +1; located in the nucleus
different isotopes of the same element will
have different properties
energy level three
holds 18 electrons
energy level four
holds 32 electrons
energy level two
holds 8 electrons
Periods
horizontal rows of elements
Mendeleev
in 1800s, created first periodic table; grouped by atomic mass rather that atomic number
Elements are abbreviated
in scientific shorthand (always first letter or two of word)
if you +/- electron from an atom
ion
name of element followed by mass number identifies
isotope
+/- neutron from atom
isotopes
Elements are classified by
metals, nonmetals, and metalloids
electrons
negative charge; outside nucleus
neutron
neutral charge; inside nucleus
nucleus
protons and neutrons located inside; electrons outside in the cloud
Atom
smallest piece of matter that still has the properties of the element
number of neutrons is found by
subtracting the mass number and the atomic number
Mass number
sum of protons and neutrons
Atomic number
the number of protons in an atom; if it's not an isotope, it tells how many neutrons and electrons are in the atom
Elements in the same group have
the same number of valence electrons
average atomic mass is closest
to it's most abundant isotope
Electron dot diagrams (Lewis)
use the element's symbol and the dots to represent the outer energy level
Groups
vertical columns on periodic table
average atomic mass
weighted average mass of the elements isotope
Quarks
what protons and neutrons are made of; six known to exist; 6th quark is the top quark
if you add or subtract a proton from an element
you get a new element
