Elements Elements are substances that cannot be broken down into simpler substances. They are the simplest substances. Every substance in the universe is a combination of one or more elements. Atoms are the smallest units of an element that have the properties of that element.

The elements and their symbols are shown on the PERIODIC TABLE How many elements are there? PERIODIC TABLE 92 elements occur naturally on Earth; 23 have been created by scientists in laboratories.

listen to the “Element Song”

Elements are arranged on the Periodic Table: Vertically into Groups Horizontally Into Periods

Why?

If you looked at one atom of every element in a group you would see…  Every atom in a group has the same number of electrons in its outermost level. For example…

The Group 2 atoms all have 2 electrons in their outer level Be (Beryllium) Atom Mg (Magnesium) Atom

The electrons in an atom’s outermost level are called the valence electrons. The number of valence electrons in an atom affects the way the atom bonds with other atoms. This is why elements in a group have similar properties– because they have the same number of valence electrons.

Electron Dot Diagrams show the number of valence electrons in an atom. Observe the electron dot diagrams of the Period 2 elements below. What do you notice? Electron Dot Diagrams

Each group has distinct properties The Periodic Table is divided into groups (vertical columns) based on the properties of each group’s elements. Groups whose elements behave very similarly are called a family.

 Soft, silvery-colored solids Have 1 valence electron Alkali Metals (Group 1)  Soft, silvery-colored solids Have 1 valence electron  Very reactive!!! especially with Halogens (Group 17) video showing alkali metals mixing with water. Stand back… sodium reacting with water more Na + H2O

Alkali Metals Lithium Sodium Potassium Rubidium Francium Cesium

Alkaline Earth Metals (Group 2) Silvery-White Solids  Have 2 valence electrons  Fairly reactive  Many are found in rocks in the earth’s crust

Alkaline Earth Metals Beryllium Magnesium Calcium Strontium Radium Barium

Transition Metals Groups 3 to 12  Most are good conductors of electricity Malleable (easily hammered into sheets) Ductile (easily extruded into wire) Solids (except for Mercury) High melting points Shiny luster

Uses of Transition Metals

Metalloids share properties with both metals and non-metals Si (Silicon) and Ge (Germanium) are very important semi-conductors. Semi-conductors are used in computer technology.

What are semiconductors used in?

Nonmetals  Solids are brittle (break easily, don’t bend) Do not conduct electricity Some are gases, some are solids, one is a liquid.

Non-Metals: Solids

Halogens (Group 17) Have 7 valence electrons Reactive, especially with Alkali Metals (Group 1)  Exist as diatomic molecules (F2, Cl2, Br2, I2), so that both atoms have a full outer electron layer. Cl Cl Remember: BRINCLHOF

Halogens

Uses of the Halogens Fluorine is put into water supplies to kill harmful bacteria and to help keep teeth healthy. Chlorine is used in swimming pools to kill bacteria in the water. Bromine is used in pesticides. Silver bromide is used in photography. Iodine is used as an antiseptic on cuts, and as an indicator for starch.

Noble Gases (Group 18)  Outer electron levels are full  Non-reactive (stable) Gases at room temperature Low melting & boiling points  Exist as single atoms rather than diatomic molecules (He, Ne, Ar, Kr, Xe, Rn)

Helium is lighter then air and is used in balloons and airships.

Jellyfish lamps made with noble gases artist- Eric Ehlenberger

Colors Noble Gases produce in lamp tubes: Ne (Neon): orange-red Hg (Mercury): light blue Ar (Argon): purple He (Helium): pale peach Kr (Krypton): silvery-white Xe (Xenon): blue-green

Lanthanide Series Actinide Series

Lanthanides & Actinides  Both are silver, silvery-white, or gray metals.  The metals have a high luster, but tarnish readily in air. The metals have high electrical conductivity.  Many fluoresce under UV light. Lanthanides are relatively soft, have high melting and boiling points, burn in air, and are very reactive. Most are widely used in lasers. Actinides are very dense radioactive metals, which combine directly with most nonmetals.

Really Important Elements 78% of the Earth’s atmosphere is Nitrogen. We are all carbon-based life forms; carbon is found in every living thing on Earth. Oxygen makes up 21% of Earth’s atmosphere, 47% of the Earth’s crust, and is found in 100% of all living things on Earth.

The 8 most common elements in Earth’s crust (by mass): 46.6% Oxygen (O) 27.7% Silicon (Si) 8.1% Aluminum (Al) 5.0% Iron (Fe) 3.6% Calcium (Ca) 2.8% Sodium (Na) 2.6% Potassium (K) 2.1% Magnesium (Mg)

Top 10 elements in the human body 1. Oxygen (65%) 2. Carbon (18%) 3. Hydrogen (10%) 4. Nitrogen (3%) 5. Calcium (1.5%) 6. Phosphorus (1.0%) 7. Potassium (0.35%) 8. Sulfur (0.25%) 9. Sodium (0.15%) 10. Magnesium (0.05%) Hydrogen Nitrogen

the only metal that is liquid at STP Some Cool Elements Mercury Bismuth the only metal that is liquid at STP

Elements used in jewelry Gold Silver Platinum

Mendeleev’s Periodic Table Dmitri Mendeleev (1834 - 1907) organized the 63 elements that were known at that time (1869) into the Periodic Table. He predicted the existence of 3 elements that had not yet been discovered, based on the gaps in his periodic table. The 3 elements were discovered later (scandium, gallium, germanium).

Early versions of Mendeleev’s table

Glenn Seaborg (1912-1999) Discovered 8 new elements Only living person for whom an element was named (Sg, seaborgium, element 106)

Other scientists who have had elements named after them… Rutherford Meitner Curie Fermi Bohr Roentgen Einstein Mendeleev