The Elements





In the universe, there are 92 naturally
occurring elements.
The other elements are synthetic, or created
in a laboratory.
Remember, that elements in Groups 1A-8A
are also called the representative elements.
Remember that the number that comes in
front of the A, tells how many valence
electrons the elements in the group have.
The electrons of all representative elements
are in the s and p blocks of the periodic table.



Remember that the elements in the same
group have the same number of valence
electrons.
The properties of the elements in a group are
not the same, but the properties are the
similar.
This is because the numbers of nonvalence
electrons is not the same.




When metals react they lose electrons.
As the atomic number increases, the
reactivity of the metals increases.
On the other hand, nonmetals, when they
react tend to gain electrons.
As their atomic number increases, their
reactivity decreases.


Some metals have more properties in
common with a neighboring group than with
the other elements in their group.
This kind of relationship is called a diagonal
relationship.






Although hydrogen is placed in
group 1A, it is not a member of
any group because it has properties of both
metals and nonmetals.
It behaves as a metal when it loses its electron.
It behaves as a nonmetal when it gains an
electron.
The universe contains more than 90% hydrogen
by mass.
Hydrogen reacts violently with oxygen in the
production of water.
The main use of hydrogen is in the production of
ammonia.






These metals are soft metals that are highly
reactive.
They easily lose their single valence electron
to form 1+ ion.
Lithium is the least reactive.
Sodium and potassium are the most
abundant alkali metals.
The most common sodium compound, is
sodium chloride or, table salt.
Potassium compounds are included in
fertilizers.

http://video.google.com/videoplay?docid=2134266654801392897








These metals are hard, shiny solids.
They are less reactive than 1A elements.
They form 2+ ions.
Beryllium is used in nuclear reactions and in alloys for
non-sparking tools.
Calcium is needed for human bone strength and
teeth.
Calcium carbonate is found in rocks, antacids, and in
abrasives.
It can also be used to make soil less acidic, remove
pollutants from smoke stacks, and to make mortar.
Magnesium is used in alloys b/c it is lightweight and
heat-resistant.
1.
Compare each of the following in terms of
group #, # of valence e-, typical ion formed,
ionization energy and reactivity.
a. Calcium and strontium
b. Lithium and francium
c. Cesium and barium
2.
Identify the following group 2A elements
based on their properties.
a. An element that forms an oxide used to line furnaces
b. An element with two valence e- that is used to
moderate neutrons in nuclear reactors


P block elements include metals, nonmetals
and metalloids.
Many of the elements can form more than
one ion.








These elements have three valence electrons.
This group includes a metalloid and all of the
others are metals.
Boron and aluminum can form 3+ ions.
Gallium and indium form 3+ and 1+ ions.
Thallium forms only 1+ ions.
Boron is found in borax, which is used as a
cleaning agent and as fireproof insulation.
Aluminum is the most abundant
metal.
Gallium is used in some thermometers.


Allotropes are forms of an elements in the
same physical state with different structures
and properties.
Alloys mixtures of metals.




These elements have 4 valence electrons.
Carbon is the most important. Branch of
chemistry called organic to study compound
compounds in cells.
Carbon takes various forms like graphite and
diamond.
Silicon is the 2nd most abundant element in
Earth’s crust, and in silica, sand, quartz and
glass.





This group has 5 valence electrons.
Nitrogen gas makes up most of the Earth’s
atmosphere.
Bacteria converts the nitrogen into usable
form for plants and animals.
Nitrogen is used to make ammonia, nitric
acid, fertilizer, dyes and explosives.
Phosphorous can be found in baking powder,
cleaning products and fertilizer.
3. Find the following pairs on the periodic
table. State the name of each. Then
compare in terms of group # and # of
valence e-. Identify each as a metal,
nonmetal or metalloid. State a use for each
element.
a. C and Pb
b. Si and P
c. Ga and N





These elements have 6 valence e-.
Oxygen is the most abundant element in
Earth’s crust.
Oxygen has 2 allotropes: O2 and O3 (ozone).
Sulfur has 10 allotropes and is used to make
sulfuric acid.
Selenium is used in solar panels and
photocopiers.






These elements have 7 valence e-.
They are highly reactive.
Fluorine is the most electronegative element,
and is used in toothpaste.
Chlorine is used as a disinfectant, bleach and
to make some plastics.
Silver bromide and iodide are used in
photography.
Iodine is important for maintaining thyroid
health.





These elements have filled outer energy levels
and are extremely unreactive.
Helium is used for balloons.
Neon is used in light displays.
Argon is used to stop reactions from taking
place.
Argon and Krypton are used to extend the life
of filaments in incandescent lightbulbs.
4.
5.
An elements is a gas at room temperature.
It does not form any compounds. It has 8
valence electrons and is higher in atomic
mass than the element phosphorous but
lower in mass than arsenic. Identify the
element’s group name and number, and
name the element.
An element is metallic and radioactive. It
has 6 valence electrons. Identify the
element’s group number and name the
element.


The transition metals make up the B groups
of the periodic table.
They can be divided in the d-block, transition
metals, and the f-block, inner transition
metals.





The final electrons of transition metals enter
a d sublevel.
They have typical metallic properties such as
malleability and electrical conductivity.
Most are hard and have high melting and
boiling points.
Transition metals generally lose their two s
electrons to form 2+ ions.
However, some can also lose d electrons and
take on higher charges.





In the d-block, positive ions that have unpaired
electrons are generally colored.
Because these electrons can move easily, these
elements can be magnetic.
If all electrons are paired the metal is
diamagnetic, that is not attracted to a magnetic
field.
If there is an unpaired electron, the metal is
paramagnetic, or slightly magnetic.
Some metals (e.g., iron, cobalt) are
ferromagnetic, or have a strong attraction to a
magnetic field.





The final e- in these metals enters the f
sublevel.
They are placed below the main body of the
periodic table.
They include the lanthanide and actinide
series.
The lanthanides have very similar properties,
are silvery metals with high melting points.
They are used in welder’s glasses, TV screens
and lasers.


The actinide series are all radioactive and
most are synthetic.
They include the transuranium elements,
elements that have an atomic number greater
than 92.