The Periodic Table of the Elements - Warren County Public ... 15 The... · The Periodic Table of...

The Periodic Table of the Elements

Ch 15 Representative and Transition Elements

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Development of the Periodic Table

•  In 1830, 55 different elements had been isolated and named-the list is still growing


Development of the Periodic Table

•  Dmitri Mendeleev- Russian Chemist published the first version of the Periodic Table in 1869

•  Arranged the elements by their atomic mass

•  Recognized patterns-elements with similar properties fell into groups

•  Left gaps for missing elements •  Made predictions for the properties of

missing elements


Today’s Periodic Table


Families Periods •  Columns of elements are

called groups or families. •  Elements in each family

have similar but not identical physical and chemical properties.

•  For example, lithium (Li), sodium (Na), potassium (K), and other members of family IA are all soft, white, shiny metals.

•  All elements in a family have the same number of valence electrons.

•  Each horizontal row of elements is called a period.

•  The elements in a period are not alike in properties.

•  In fact, the properties change gradually and predictably across even given row.

•  The first element in a period is always an extremely active solid. The last element in a period, is always an inactive gas.


Properties of Metals

•  good conductors of heat and electricity.

•  shiny. •  ductile (can be stretched into

thin wires). •  malleable (can be pounded

into thin sheets). •  A chemical property of metal

is its reaction with water which results in corrosion.


Properties of Non-Metals

•  Poor conductors of heat and electricity.

•  Not ductile or malleable.

•  Solid non-metals are brittle and break easily.

•  Dull •  Many are gases. Sulfur


Properties of Metalloids

•  Metalloids (metal-like) have properties of both metals and non-metals.

•  Solids that can be shiny or dull.

•  Conduct heat and electricity better than non-metals but not as well as metals.

•  Ductile and malleable. Silicon


The most abundant element in the earth’s crust is

oxygen.


Key to the Periodic Table •  Elements are organized on

the table according to their atomic number, usually found near the top of the square. –  The atomic number refers

to how many protons an atom of that element has.

–  For instance, hydrogen has 1 proton, so it’s atomic number is 1.

–  The atomic number is unique to that element. No two elements have the same atomic number.


What’s in a square?

•  Different periodic tables can include various bits of information, but usually: –  atomic number –  symbol –  atomic mass –  number of valence

electrons –  state of matter at

room temperature.


Symbols

•  All elements have their own unique symbol.

•  It can consist of a single capital letter, or a capital letter and one or two lower case letters.

C Carbon

Cu Copper


Atomic Mass and Isotopes

•  While most atoms have the same number of protons and neutrons, some don’t.

•  Some atoms have more or less neutrons than protons. These are called isotopes.

•  An atomic mass number with a decimal is the total of the number of protons plus the average number of neutrons.


Atomic Mass Unit (AMU)

•  The unit of measurement for an atom is an AMU. It stands for atomic mass unit.

•  One AMU is equal to the mass of one proton.


Atomic Mass Unit (AMU)

•  There are 6 X 1023 or

600,000,000,000,000,000,000,000 amus in one gram.

•  (Remember that electrons are 2000 times smaller than one amu).


Groups 1 and 2

•  Always found in nature combined with other elements

•  Active metals – Readiness to form new substances

•  All metals except hydrogen


Group 1-Alkali Metals

•  Silvery solids •  Low densities •  Low melting points •  Increase in reactivity as you

move from top to bottom – Most reactive is Francium(Fr)


What does it mean to be reactive?

•  We will be describing elements according to their reactivity.

•  Elements that are reactive bond easily with other elements to make compounds.

•  Some elements are only found in nature bonded with other elements.

•  What makes an element reactive? –  An incomplete valence electron level. –  All atoms (except hydrogen) want to have 8

electrons in their very outermost energy level (This is called the rule of octet.)

–  Atoms bond until this level is complete. Atoms with few valence electrons lose them during bonding. Atoms with 6, 7, or 8 valence electrons gain electrons during bonding.


Alkali Metals

•  Uses: – Lithium(Li)—batteries – Sodium(Na)—table salt – Sodium(Na) and Potassium(K)—

dietary requirements


Group 2-Alkaline Earth Metals

• Each is denser, harder, and has a higher melting point than the alkali metal in same period

• Reactive, but not as reactive as alkali metals


Alkaline Earth Metals

• Uses: – Beryllium(Be)—found in

gems emerald and aquamarine

– Magnesium(Mg)—found in chlorophyll of green plants


Groups 13 thru 18 •  Not all solid metals •  A single group can contain

metals, nonmetals, and metalloids

•  A single group can also have members that are solids, liquids, and gases


Group 13—Boron Family •  All metals except boron(B)

(brittle, black metalloid) •  Used to make a variety of

products – Cookware—boron(B) – Soft-drink cans—aluminum(Al) – Computer chips--gallium(Ga)


Group 14—Carbon Group

•  Carbon(C)—nonmetal –  Diamond and graphite –  Found in all living things

•  Silicon(Si) & Germanium(Ge)—metalloid –  Semiconductors –  Computer chips

•  Tin(Sn) & Lead(Pb)-metal –  Two heaviest elements in group –  Lead—x-ray aprons, car batteries –  Tin—pewter, toothpaste, coating for steel

cans


Group 15—The Nitrogen Group

•  Nitrogen(N) & Phosphorus(P) –  Nonmetals –  Required by living things –  Part of DNA

•  Nitrogen(N) –  80% of air you breathe –  Get nitrogen for body from eating plants

•  Phosphorus(P) –  White phosphorus—can’t be exposed to

air—it will explode !! –  Red phosphorus—used for head of

matches –  Also needed for healthy teeth and bones


Group 16—the Oxygen Family

•  Oxygen(O) –  20% of Earth’s atmosphere –  Required for combustion –  Ozone shields organisms from radiation

•  Sulfur(S) –  Solid, yellow nonmetal –  Used to make sulfuric acid

•  Paint, fertilizer, detergent, rubber •  Selenium(Se)

–  Conducts electricity when exposed to light

–  Used in solar cells, photographic materials


Group 17—The Halogen Group

•  All non-metals except for astatine (radioactive metalloid)

•  Means “salt-former” – Example, table salt—sodium

chloride •  Most reactive is fluorine •  Least reactive is iodine •  Chlorine(Cl)kills bacteria in

water


Group 18—The Noble Gases

•  Rarely combine with other elements •  Great for signs

–  Each glows a different color light when electricity is passed through

•  Helium(He) –  Less dense than air –  Great for balloons

•  Argon(Ar) –  Most abundant

•  Krypton(Kr) –  Used to illuminate landing strips

•  Radon(Rn) –  Radioactive; produced naturally –  Harmful; can cause lung cancer


Transition Elements

•  Groups 3-12 •  All metals •  Most found combined with other

elements in ores •  Few found as pure elements

gold(Au) and silver(Ag)


Iron Triad

•  Elements in period 4 –  Iron, cobalt, nickel

•  Have magnetic properties •  Industrial magnets—alloy of nickel,

cobalt, aluminum •  Nickel used in batteries •  Iron is necessary in hemoglobin to

transport oxygen in body •  Iron also combined with other metals

to produce steel


Uses of Transition Elements

•  Tungsten(W)—highest melting point of any metal – Used as filament in light bulbs

•  Mercury(Hg)—lowest melting point – Used in thermometers and

barometers – Only metal liquid at room

temperature – Poisonous to living things


Uses of Transition Elements

•  Chromium(Cr)—comes from Greek word for color, chroma – Used in paints

•  Platinum(Pt) group – Ruthenium, rhodium, palladium,

osmium, iridium, and platinum – Can be used as catalysts – Used to produce electronics


Inner Transition Metals

• Lanthanide Series • Actinide Series


Lanthanides #58-71 •  Also called rare earth elements •  Usually found in combination with

oxygen in Earth’s crust •  Soft metals that can be cut with a

knife


Actinides # 90-103 •  All radioactive •  Thorium(Th), protactinium(Pa),

uranium(U) are only ones found naturally on Earth

•  Plutonium(Pu)—used to fuel nuclear power plants

•  Americium(Am)—used in smoke detectors

•  Californium-252(Cf)—used to kill cancer cells

•  Synthetic-Not occur in nature

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