Download Atom - WCHS Physical Science

Warm-Up 9/2
• What does the atomic
number of an element
tell us about the
element?
Warm-Up 9/6
•What is the mass
number of an atom
equal to?
Warm-up 9/7
How can you find the
number of neutrons in
an atom?
Warm-up 9/8
• How many electrons can
there be in the :
• First energy level?
• The second energy level?
• The third energy level?
The Atom
• SPS1 Students will investigate our
current understanding of the atom.
a. Examine the structure of the atom in
terms of
• proton, electron, and neutron locations.
• atomic mass and atomic number.
• atoms with different numbers of neutrons
(isotopes).
• explain the relationship of the proton
number to the element's identity.
• SPS4 Students will investigate the
arrangement of the Periodic Table.
a. Determine the trends of the following:
• Number of valence electrons
• Types of ions formed by representative
elements
• Location of metals, nonmetals, and
metalloids
• Phases at room temperature
Atom
Democritus came up with the
idea of an atom. (His idea
wasn’t accepted much
because he didn’t
experiment).
The word atom came from a
Greek word that meant
“unable to be divided”.
•Atom – the smallest part of an element
with all of the properties of the element
Parts of the atom
• Electrons:
• Negative charge
• Smallest particles
• Located outside of
atom
• Protons:
• Positive Charge
• Located in nucleus
(center) of atom
Parts of the atom
• Neutrons:
• No charge (neutral)
• Located in nucleus of atom
Structure of the atom
electron
neutron
proton
Bohr’s model of the atom
• He said that
electrons orbited
the nucleus in
energy levels
like planets
around the sun.
Modern Model of atom (wave
model)
• Based on probability
• Says that an electron’s
location can’t be
determined exactly
Electron Cloud Model
• Another name
for modern
model
Valence Electrons
• Electrons in the outermost energy
level of an atom
• First level – 2 electrons
• Second level – 8 electrons
• Other levels can hold more electrons
but are considered stable with 8
electrons
Atomic Mass
• The mass of an atom is
measured in something
called atomic mass units
(amu).
• The atomic mass unit is
defined as 1/12th the
mass of a carbon atom.
Atomic Number
• Atomic Number is equal to the
number of protons in the nucleus of
an atom.
• The number of protons in an atom
determines the identity of an
element.
Atomic Number, continued
• The periodic table is arranged
by increasing atomic number.
• The number of protons = the
number of electrons.
Mass Number
• Mass Number – the sum of the
protons and neutrons in the nucleus
of an atom
Neutrons
Equation:
# of neutrons = mass # – atomic #
Isotopes – atoms of the same
element with different numbers
of neutrons
Isotopes
More Isotopes
History of the Periodic Table
• Dmitri Mendeleev invented the first
periodic table. He arranged it
according to increasing atomic mass.
• Henry Moseley arranged the
modern periodic table. He
arranged it according to
increasing atomic number.
Arrangement of Periodic Table
• Groups – vertical columns, also called
families – 18 groups – elements in groups
have similar properties
• Periods – horizontal rows, 7 periods
The end.