Transcript The periodic table is a map of the elements.

The periodic table is a map
of the elements.
Section 1.3D
The periodic table has distinct
regions.
• An atom’s position on the periodic table indicates the
properties of its element.
• 3 main regions
– Metals on the left
– Nonmetals (except hydrogen) on the right
– Metalloids in between
An element’s position in the
table also indicates how reactive
it is.
• Reactive – how likely an elements is to undergo a
chemical change
• Most elements are somewhat reactive and combine
with other materials.
• The atoms of the elements in Groups 1 and 17 are the
most reactive.
• The elements of Group 18 are the least reactive.
Most elements are metals.
• Metals – elements that conduct electricity and heat
well and have a shiny appearance
• Malleable - can be shaped easily by pounding, bending,
or being drawn into a long wire
• Metals are solid at room temp. (except mercury –
liquid at room temp.)
Reactive Metals
• Group 1 (alkali metals)
– Very reactive
– Sodium and potassium stored in oil to keep away from air
(react rapidly with oxygen and water vapor when exposed to
air)
– Sodium and potassium ions, Na+ and K+, are important for life
and play an essential role in the functioning of living cells
Reactive Metals
• Group 2 (alkaline earth metals)
– Less reactive than the alkali metals, but still more reactive
than most other metals
– Calcium ions – essential part of your diet (bones and teeth)
– Magnesium – a light, inexpensive metal that is often
combined with other metals when a lightweight material is
needed (airplane frames)
Transition Metals
•
•
•
•
Groups 3-12
Copper, gold, silver, iron
Generally less reactive than most other metals
Jewelry and coins from gold and silver because they
are easily shaped and do not react easily
• Dimes and quarters – copper and nickel
• Pennies – zinc with a coating of copper
Transition Metals
• Important for industry
– Steel is made partly of iron and is used for bridges and
buildings.
– Most electric wires are made of copper
– Copper is used to make water pipes
Important for technology
– Tungsten – tiny coil of wire inside incandescent light bulbs
– Platinum – in the catalytic converters that reduce pollution
from cars
Transition Metals
• Alloys – two or more metals are combined to make
materials that are stronger, less likely to corrode, or
easier to shape than pure metals
• Steel – stronger than the pure iron that it contains
and includes nickel, chromium, or manganese
• Brass – copper and zinc and is stronger than either
metal alone
• Jewelry – alloy of copper and silver, stronger than
pure silver
Rare Earth Elements
• Rare earth elements – the elements in the top row of
the two rows of metals that are usually shown outside
the main body of the periodic table (makes the table
more compact)
• Often referred to as lanthanides – they follow the
element lanthanum on the table
Rare Earth Elements
• Called rare earth elements because scientists once
thought that they were only available in small amounts
in Earth’s crust
• As mining methods improved, scientists learned that
they were not so rare – just hard to isolate in pure
form
• Uses
– Europium (Eu) – coating for some television tubes
– Praseodymium (Pr) – protective coating against harmful
radiation in welder’s helmets
Nonmetals and metalliods have a
wide range of properties.
• Nonmetals – to the right side of the periodic table
and have properties the opposite of metals
• Many are gases at room temp, and one – bromine – is a
liquid
• Solid nonmetals – often have dull surfaces and cannot
be shaped by hammering or drawn into wires
• Generally poor conductors of heat and electric
current
Halogens
• Group 17 – from the Greek words meaning “forming
salts”
• Very reactive nonmetals that easily form compounds
called salts with many metals
• Often used to kill harmful organisms (ex. Chlorine is
used to clean drinking water and prevent growth of
algae in swimming pools/iodine – used in hospitals to
kill germs on skin)
Noble Gases
• Group 18 – noble, or inert gases – almost never react
with other elements
• Argon gas – makes up about 1% of the atmosphere
• Colorful lights in signs – tubes filled with neon,
krypton, xenon, or argon gas
Metalloids
• Metalloids – elements that have properties of both
metals and nonmetals
• Lie on either side of a zigzag line separating metals
from nonmetals
• Most common metalloid – silicon (2nd most common
atoms in Earth’s crust)
Metalliods
• Make up semiconductors found in electronic devices
(conduct electricity under some conditions and not
under others)
• Silicon, gallium, and germanium are 3 semiconductors
used in computer chips
Some atoms can change their
identity.
• The identity of an element is determined by the
number of protons in its nucleus.
• Chemical changes do not affect the nucleus, so they
don’t change one type of atom into another.
• Isotopes have different numbers of neutrons and
stability depends on the right balance of protons and
neutrons.
• Too few or too many neutrons = unstable nucleus –
particles are produced from the nucleus to restore
balance
Some atoms can change their
identity.
• When the particles are released, the change is
accompanied by a release of energy.
• If the production of particles changes the number of
protons, the atom is transformed into an atom of a
different element.
• Radioactivity – the process by which atoms produce
energy and particles (named by physicist Marie Curie
in the early 1900’s)
Some atoms can change their
identity.
• Most elements have radioactive isotopes, but are rare
for small atoms
• Beyond bismuth (Bi) all of the isotopes are
radioactive
• Study radioactivity with a Geiger counter, which
detects the particles from the breakup of the
nucleus with audible clicks; more clicks = more
particles are being produced
Uses of Radioactivity in
Medicine
• Radiation produced by unstable nuclei is used in
hospitals to diagnose and treat patients
– To destroy harmful tumors without operation
– To monitor the activity of certain organs in the body
In large doses it is harmful to living things and should be
avoided
– Can damage or kill cells
– Energy from its particles can burn the skin
– Prolonged exposer has been linked to cancer and other
health problems
Radioactive Decay
• Radioactive atoms
produce energy and
particles = identity
changes because # of
protons changes =
radioactive decay
• Over time, all of the
atoms of a radioactive
isotope will change into
atoms of another
element.
• Radioactive decay occurs at a
steady rate characteristic of
the particular isotope.
• Half-life – the amount of
time that it takes for onehalf of the atoms in a
particular sample to decay
Half-Life
• 1000 atoms of a radioactive
isotope with a half-life of 1
year = 500 would change into
another element over the
course of a year
• In the next year, 250 more
atoms would decay, (and so
on)
• Half-life is not affected by
conditions such as temp. or
pressure.
• Half-lives can range from a
small fraction of a second to
many billions of years.