Structure of an Atom
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Transcript Structure of an Atom
Structure of an Atom
What Is an Atom?
An atom is often referred to as the
building block of matter. Atoms have
a nucleus surrounded by an electron
cloud
Atoms are composed of smaller
subatomic particles in an atom. The
proton, neutron, and electron.
Each element is composed of one
type of atom and can not be broken
down into a simpler substance
Inner Structure of an Atom
• Nucleus - Small, dense, positively
charged center of the atom which
contains most of the atom’s mass
• The nucleus contains subatomic
particles that have certain
characteristics:
Protons
(p+) - positively charged
particles in the nucleus of the atom,
contribute to the atom’s mass
Neutrons (no)- particles in the nucleus
that have no charge, but contribute to
the atom’s mass NEUTRAL
Outer Structure of an Atom
●Electron cloud - an area encircling
the nucleus where electrons are
likely to be found
●The cloud contains energy levels
electrons (e-)are negatively charged
particles located in specific energy levels
energy levels completely surround the
nucleus
there is a specific order for the electrons
to fill the energy levels
Outer Structure of an Atom
●Energy levels completely surround
the nucleus
Maximum
of 2
electrons
Nucleus
Maximum
of 50
electrons
Maximum
of 8
electrons
Maximum
of 18
electrons
Maximum
of 32
electrons
Outer Structure of an Atom
●valence electrons are in the
outermost energy level and are the
electrons involved in bonding
valence electrons determine the
number of bonds an atom can
form
an atom is most stable when its
outermost energy level is full
Atom Characteristics
The number of protons in the nucleus is
the atomic number of that atom.
The number of protons (+) equals the
number of electrons (-) in a neutral atom
The mass number is the mass of the
protons plus the mass of the neutrons
mass is reported in the SI units atomic
mass units (amu)
Protons and neutrons each are given
an amu of 1
Electrons have a mass of nearly zero
Decoding Atom Information
# of
protons
Atomic
mass
6
C
carbon
12.011
Symbol
Name
Decoding Atom Information:
# of protons =
# of electrons
in a neutral
atom
Atomic mass is a
weighted average
of all the isotopes
of an element
6
C
carbon
12.011
The mass number of an atom is for
a particular isotope of that element
Mass number is the total number of
protons and neutrons in the
nucleus
Example for C-12:
◦ 6 protons + 6 neutrons= 12
◦ 12 is the mass number for Carbon-12
*13 is the mass number for Carbon-13
and comes from C-13 having 6 protons
and 7 neutrons