chem2

Atomic Structure and
the Periodic Table
1. Students can describe the parts of an atom
2. Students can read the element information on
the periodic table
3. Students can describe the reactivity of alkali
metals
4. Students can describe how various types of
bonding in different categories of materials
effects their behavior

Atoms
• smallest particle of an element that has
the properties of the element
• made of 3 basic subatomic particles
• there are now many more subatomic particles
– theoretical physics

• nucleus
• small, dense center of atom
• contains almost all the mass of the atom
• contains protons and neutrons

• Atomic Mass Unit (amu)
• metric unit to measure the mass of VERY
small objects (particles)
• a unit to measure the mass of atoms

Subatomic Particles
Name Protons (p or +) Neutrons (n) Electrons (e - )
Charge +1 No charge -1
Location in nucleus in nucleus in shells around
nucleus
Mass ≈ 1 amu ≈ 1 amu ≈ 2000 x
smaller
“Job”
Determines
identity of
element
Supplies proper
mass to hold
nucleus together
Determines
bonding/
how it reacts
Number

Subatomic Particles
Name Protons (p or +) Neutrons (n) Electrons (e - )
Charge +1 No charge -1
Location in nucleus in nucleus in shells around
nucleus
Mass ≈ 1 amu ≈ 1 amu ≈ 2000 x
smaller
“Job”
Determines identity
of element
Supplies proper
mass to hold
nucleus together
Determines
bonding/ how it
reacts
Number Atomic # Atomic mass –
atomic # =
# of neutrons
Same as #
of protons

# of protons
• atomic number
• whole number on periodic table
• number of protons in an atom of an element
• does NOT vary in an element – the same in
all atoms of an element

# of electrons
• atoms are neutral
• (+) = (-)
• # of protons = # of electrons
• p = e -

• atomic mass (weight)
• decimal number on the periodic table – it is
for all the atoms of the element
• number of protons plus the number of
neutrons – it’s an average on the table
• weighted average of all the isotopes of
that element
• the mass of one atom is a whole number

• Isotopes
• iso = same
• atoms of the same element with different
numbers of neutrons
• have different atomic masses but the same
atomic number
• some are stable, some are radioactive
(carbon-12 and carbon-14)

Free Write
• What do you know about:
• atoms
• the periodic table

Periodic Table
• How is the periodic table arranged?
• arranged by increasing atomic number
• rows
• called periods
• tells number of electron shells
• number them down the left side of the
periodic table – 1 through 7

Periodic Table
• columns
• called families or groups
• elements in same column have similar
chemical properties
• same number of valence electrons

Ion
• atom with a charge
• atom has gained or lost electrons
• gained e - = (-) charge
• lost e - = (+) charge
• (+) ion = cation
• (-) ion = anion

Column 1
• alkali metals
• want to give away one electron
• most reactive metals

Alkali metals on the show
brainiac

Bonding
• atoms achieve a stable number of
electrons (ionic and covalent)
• involves valence (outer) electrons
• make compounds and/or solids

Metallic Bonding
All pure metals have metallic bonding and
therefore exist as metallic structures. Metallic
bonding consists of a regular arrangement of
positive ion cores of the metals surrounded by a
mobile delocalized sea of electrons.

Metallic Bonding
• Each atom donates its valence electrons to
the whole
• Atom therefore becomes a cation (here called
an ion core)
• Donated electrons form an electron cloud
surrounding all the ion cores
• Electron cloud binds all the ion cores together
by coulombic forces

Metallic Bonding
• Valence electrons are delocalized:
• Shared by all atoms in the material
• Electrons are free to drift throughout the
material
• Provides unique properties only found in
metals
• shiny metallic luster
• good electrical and thermal conductivity
• many others ...

Metallic Bonds: Mellow dogs with plenty of
bones to go around
These bonds are best imagined as a room full of
puppies who have plenty of bones to go around and
are not possessive of any one particular bone. This
allows the electrons to move through the substance
with little restriction. The model is often described
as the "kernels of atoms in a sea of electrons."

Ionic Bonding
(ceramics and polymers)

Ionic Bonds: One big greedy thief dog!
Ionic bonding can be best imagined as one big greedy
dog stealing the other dog's bone. If the bone
represents the electron that is up for grabs, then when
the big dog gains an electron he becomes negatively
charged and the little dog who lost the electron
becomes positively charged. The two ions (that's where
the name ionic comes from) are attracted very strongly
to each other as a result of the opposite charges.

Sodium lets Chlorine use its valance electron

Covalent Bonding
(Ceramics)

Covalent Bonds: Dogs of equal strength.
Covalent bonds can be thought of as two or more dogs
with equal attraction to the bones. Since the dogs
(atoms) are identical, then the dogs share the pairs of
available bones evenly. Since one dog does not have
more of the bone than the other dog, the charge is
evenly distributed among both dogs. The molecule is not
"polar" meaning one side does not have more charge than
the other.

Polar Covalent Bonds: Unevenly matched but
willing to share.
These bonds can be thought of as two or more dogs that
have different desire for bones. The bigger dog has
more strength to possess a larger portion of the
bones. Sharing still takes place but is an uneven
sharing. In the case of the atoms, the electrons spend
more time on the end of the molecule near the atom
with the greater electronegativity (desire for the
electron) making it seem more negative and the other
end of the molecule seem more positive.

• http://www.bbc.co.uk/scotland/education/bitesize/higher/
chemistry/energy/bsp1_rev.shtml
• Read the 4 slides and take the quiz at the end
• Patterns in the periodic table
• http://www.ewart.org.uk/science/structures/str13.htm
• Ionic bonding Electron numbers ions and aions
• http://www.ewart.org.uk/science/structures/str14.htm
• Covalent bonding
• http://www.ewart.org.uk/science/structures/str7.htm
• Structure of the atom