Download The Atom

The Atom
Chemistry
Vocabulary and Notes
What is an atom?
An atom is the smallest
particle into which an
element (such as gold) can
be divided and still
maintain the properties of
that element.
Vocabulary - 1
• ELEMENT -substance that cannot be
broken down into other substances
by chemical/physical means
• ATOMIC NUMBER -number of protons
in nucleus
• ATOMIC MASS UNIT (amu)-unit used
to measure particles in atoms
• VALENCE ELECTRON - electrons
located farthest away from nucleus
• CHEMICAL BOND - force that holds
chemicals together
ATOMIC STRUCTURE
Atoms are made up of even smaller
particles called protons, neutrons, and
electrons.
PROTONS (+)– positively charged particles
located in the nucleus
NEUTRONS (0)– electrically neutral particles
located in the nucleus
ELECTRONS (-)– negatively charged particles
found outside the nucleus
ATOM
Atom Notes
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Nucleus-core of atom, made of proton (+), neutrons
Atom neutral when protons = electrons (-)
Atomic number = number of protons
AMU measures particles in atom
Electrons roam around nucleus in electronic cloud –
are in constant motion
• Protons have almost 2000 times as much mass as
electrons
• Electrons attract protons in nearby atoms
• Attraction forms molecules
Atom Notes - cont.
• Atomic Mass = number of protons + number of
neutrons
• 1st shell = 2
• 2nd shell = 8
• 3rd shell = 18
• 4th shell = 32
• 5th ,6th,7th have various amounts, depending on
type of molecule formed with max of 32, 18, and 2
respectively
• Most of the atom’s volume is the space where the
electrons move
Valence Electrons
• Are the electrons that
are farthest away from
the nucleus
• Determines many
properties of the atom
and therefore of the
element
• Forms chemical bonds
with other atoms
• Can range from 1 to 8
• Are represented by an
electron dot diagram