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Periodic Table Groups and Trends. The Main-Group Elements. Elements in Groups 1a, 2a, and 3a-8a are known as the main group elements. Main group elements are in the s-block and the p-block. The electron configurations of these are regular and consistent.

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the main group elements
The Main-Group Elements
  • Elements in Groups 1a, 2a, and 3a-8a are known as the main group elements.

Main group elements are in the s-block and the p-block.

The electron configurations of these are regular and consistent.

The elements in each group have the same number of valence electrons.

group 1 the alkali metals
Group 1—The Alkali Metals
  • Elements in Group 1 are called alkali metals.
  • These include lithium, sodium, potassium, rubidium, cesium and francium.
  • Alkali metals are called this because they all react with water to make alkaline solutions.

All Alkali Metals are extremely reactive.

They are usually stored in oil to keep them from reacting with the oxygen and water found in the air.

alkali metals group 1
Alkali Metals—Group 1
  • Alkali Metals all have 1 electron in their

outside orbital.

(They are very

likely to lose

this electron

and become

a positive ion.

More about

ions later!)

alkali metals are very reactive
Alkali Metals are Very Reactive
  • Because of their high reactivity, alkali metals are never found in nature as pure elements, but are found combined with other elements in compounds.
  • All of these elements are so soft,

they can easily be cut with a knife.

The freshly cut surface of an alkali metal is shiny, but it dulls quickly as the metal reacts with oxygen and water in the air.

Sodium metal

group 2 the alkaline earth metals
Group 2—The Alkaline-Earth Metals
  • Group 2 elements are called the alkaline-earth metals.
  • Like the alkali metals, the alkaline-earth metals are highly reactive, so they are usually found in compounds.
  • These include beryllium,

magnesium, calcium,

strontium, barium, and


group 2 the alkaline earth metals1
Group 2-The Alkaline Earth Metals
  • The alkaline earth metals are slightly less reactive than the alkali metals.
  • These elements have 2 valence electrons.
  • They are harder than alkali metals and have higher melting points.

Beryllium is found in emeralds, which is a variety of the gemstone beryl.

Bones are made primarily of calcium phosphate.

Marble is made of calcium carbonate.

group 17 the halogens
Group 17—The Halogens
  • The Halogens are the most reactive nonmetal elements.
  • They all have 7 valence electrons in their outside orbital—just one short of a stable


These include fluorine,

chlorine, bromine, iodine,

and astatine.

group 17 the halogens1
Group 17—the Halogens
  • When the halogens react, they often gain the one electron needed to have eight valence electrons (a filled outer energy level).
  • Because the alkali metals (Group 1) have one valence electron, they are ideally suited to react with a halogen.

Sodium (an alkali metal) will easily react with Chlorine (a halogen) to form sodium chloride (NaCL), table salt.

  • Halogens can exist as diatomic molecules. Examples: F2, Cl2, Br2, and I2.
  • Do you want to hear the Halogen Song?
the halogen song
The Halogen Song
  • OK, Remember—you asked for it!
  • Disclaimer: I had nothing to do with the making of this YouTube video and I am not responsible for the feelings that ensue
  • Now for some Game show Fun!
group 18 the nobel gases
Group 18: The Nobel Gases
  • Group 18 elements are called the Noble Gases.
  • These elements have a full set of electrons in their outermost energy level.
  • Except for Helium, all noble gases have an outer shell with 8 electrons (2 in s, 6 in p).

These consist of Helium, Neon, Argon, Krypton, Xenon and Radon

group 18 noble gases
Group 18: Noble Gases
  • The noble gases are un-reactive because they are very stable with a full outer orbital.

hydrogen is in a class by itself
Hydrogen is in a Class By Itself
  • Hydrogen is the most common element in the universe. It is estimated that 3 out of 4 atoms in the universe are hydrogen atoms.
  • Because it consists of only 1 proton and 1 electron, hydrogen behaves unlike any other element.
  • With its one electron, hydrogen can react with many other elements, including oxygen.
  • Hydrogen gas and oxygen gas react explosively to form water.

One example of the power of this reaction occurred in 1937 when the German airship, the Hindenberg burst into flames while trying to land in Lakehurst, New Jersey. 38 people were killed in the explosion.

hydrogen fuel cells the cars of the future
Hydrogen Fuel Cells—the Cars of the Future?
  • One promising technology that car companies like Toyota have been pursuing is the hydrogen fuel cell. Fuel cells combine hydrogen gas with oxygen from the air to create a stream of electrons that can power electric motors like this car.
most elements are metals
Most Elements are Metals

In this Periodic Table, all of the elements shown in blue are metals.

what are metals
What are Metals?
  • All metals are excellent conductors of electricity—this is the one property that distinguishes metals.
  • Even the least conductive metal conducts electricity 100,000 times better than the best nonmetallic conductor does!
  • Metals are excellent conductors of heat.
  • Some metals, such as bismuth and manganese, are very brittle.
  • Others, such as gold and copper are ductile and malleable. (Ductile means it can be squeezed into a wire. Malleable means that the metal can be hammered and rolled into sheets.)
metals vs nonmetals
Metals vs. Nonmetals
  • Metals
    • are good conductors of electricity.
    • except for mercury, are solids at room temperature.
  • Nonmetals
    • are poor conductors of electricity.
    • exhibit a wide variety of properties.
    • may be solids, liquids or gases at room temperature.
semi conductors
  • These elements are also called metalloids.
  • These elements are on a jagged line because they separate the metals from the non-metals.
  • These elements exhibit

characteristics of both

metals and non-metals.

They conduct electricity

better than non-metals,

but not as good as metals.

transition metals
Transition Metals
  • The transition metals constitute Groups 3 through 12.
  • The transition metals do not have identical electron configurations.
  • Like other metals, transition

metals are good conductors

of heat and electricity. They

are also ductile and malleable.

transition metals1
Transition Metals
  • A transition metal may lose different numbers of valence electrons depending on the element it reacts with.
  • Transition metals are less reactive than alkali metals and alkaline-earth metals.

Some metals are so un-reactive, they seldom form compounds with other elements. Examples are Gold, Platinum, and Palladium (AKA: precious metals). Other than the noble gases, these three are the most un-reactive atoms and most often exist in nature as pure elements.

  • Part of the last two periods of transition metals are placed at the bottom of the periodic table.
  • The elements in the first of these 2 rows are called the Lanthanides.
  • Lanthanides are called this

because their atomic numbers

follow the element lanthanum.

  • Lanthanides are shiny metals similar in reactivity to the alkaline-earth metals.
  • The lanthanide elements, along with the chemically similar elements scandium and yttrium, are sometimes called the rare earth elements (however, they are neither rare or found only in the Earth!).

Lanthanide oxides: clockwise from top center: praseodymium, cerium, lanthanum, neodymium, samarium and gadolinium.

  • The elements in the 2nd of the two rows at the bottom of the periodic table are called the Actinides.
  • They are called this because they follow actinium.
  • Actinides are unique in that their nuclear structures are more important than their electron configurations.
  • Because their nuclei are unstable, and spontaneously break apart, all actinides are radioactive.
  • The best-known actinides are uranium and plutonium.

The nuclear bomb dropped on Nagasaki to end WWII had a plutonium charge.

many actinides are man made
Many Actinides are Man-Made
  • Actinides with the highest mass numbers are synthesized by bombarding uranium, plutonium, curium and californium with ions of nitrogen, oxygen, carbon, neon or boron in a particle accelerator.

Glenn T. Seaborg and his group at the University of California at Berkeley synthesized Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No and element 106, which was later named seaborqium in his honor while he was still living.

periodic table trends
Periodic Table Trends
  • The arrangement of the periodic table reveals trends in the properties of elements.
  • A trend is a predictable change in a certain direction.
ionization energy
Ionization Energy
  • Ionization Energy is the energy required to remove an electron from an atom or an ion.
  • Ionization Energy Decreases as you Move Down a group.
ionization energy1
Ionization Energy
  • As you move down a group, there are more and more electrons shielding the protons from the outer electrons.

Because there are more and more electrons shielding the outer electrons from the +-charged nucleus, it is easier to strip off electrons from the outer energy level. Therefore, ionization energy decreases.

ionization energy2
Ionization Energy
  • Ionization Energy increases as you move across a period.
  • As you move to the right, you are adding more and more protons.

Ionization Energy increases because it takes MORE energy to pull electrons away from an atom with more protons.

atomic radius
Atomic Radius
  • The size of an atom depends on the volume occupied by the electrons around the nucleus.
  • Atomic Radius increases as you move down a group.
atomic radius1
Atomic Radius
  • Atomic Radius decreases as you move across a period.
  • The increased number

of protons pulls the

electrons closer to the

nucleus, which makes

the atom slightly

smaller (even though

there are more electrons!)

  • Electronegativity is a measure of the ability of an atom in a chemical compound to attract electrons. High electronegativity means the compound will attract electrons easily.
  • Electronegativity decreases as you move down a group.
  • Even though the atoms are getting larger, electron shielding still has an effect. In the larger atoms, the distance between the nucleus and the outer electron orbital is greater.

Electron shielding makes it less likely that a larger atom can attract an electron.

  • Electronegativity increases as you move across a period. The effective nuclear charge (+) becomes greater as more and more protons are added.
  • The atoms towards the right side are more likely to pull electrons (more electronegative)