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CHEMISTRY - ELEMENT OF THE DAY - URANIUM

Atomic Number: 92

Phase at Room Temperature: Solid
Element Classification: Metal

Period Number: 7    Group Number: none    Group Name: Actinide

Radioactive

What's in a name? Named for the planet Uranus.

Say what? Uranium is pronounced as you-RAY-nee-em.

You know uranium as a radioactive element, found in bombs, nuclear power plants and hardened metals. It's also found in some decorative glassware, called "vaseline glass", where the uranium compounds contribute a yellowish-green fluorescent color. How much do you know about this element? 

1. Pure uranium is a silvery-white metal.
2. The atomic number of uranium is 92, meaning uranium atoms have 92 protons and usually 92 electrons. The isotope of uranium depends on how meany neutrons it has.
3. Because uranium is radioactive and always decaying, radium is always found with uranium ores.
4. Uranium is slightly paramagnetic.
5. Uranium is named for the planet Uranus.
6. Uranium is used to fuel nuclear power plants and in high-density penetrating ammunition. A single kilogram of uranium-235 theoretically could produce ~80 terajoules of energy, which is equivalent to the energy that could be produced by 3000 tonnes of coal.
7. Natural uranium ore has been known to fission spontaneously. The Oklo Fossil Reactors of Gabon, West Africa, contain 15 ancient inactive natural nuclear fission reactors. The natural ore fissioned back at a prehistoric time when 3% of the natural uranium existed as uranium-235, which was a high enough percentage to support a sustained nuclear fission chain reaction.
8. The density of uranium is about 70% higher than lead, but less than that of gold or tungsten, even though uranium has the second-highest atomic weight of the naturally occurring elements (second to plutonium-244).
9. Uranium usually has a valence of either 4 or 6.
10. Health effects of uranium typically are not related to the element's radioactivity, since the alpha particles emitted by uranium cannot even penetrate skin. Rather, the health impact is related to the toxicity of uranium and its compounds. Ingestion of hexavalent uranium compounds can cause birth defects and immune system damage.
11. Finely divided uranium powder is pyrophoric, meaning it will ignite spontaneously at room temperature.

CHEMISTRY - ELEMENT OF THE DAY - LITHIUM

3

Li

Lithium

6.941

Atomic Number: 3

Atomic Weight: 6.941

Phase at Room Temperature: Solid

Element Classification: Metal

Period Number: 2    Group Number: 1    

Group Name: Alkali Metal

What's in a name? From the Greek word for stone, lithos.

Say what? Lithium is pronounced as LITH-ee-em.

History and Uses:

Lithium was discovered in the mineral petalite (LiAl(Si₂O₅)₂) by Johann August Arfvedson in 1817. It was first isolated by William Thomas Brande and Sir Humphrey Davy through the electrolysis of lithium oxide (Li₂O). Today, larger amounts of the metal are obtained through the electrolysis of lithium chloride (LiCl). Lithium is not found free in nature and makes up only 0.0007% of the earth's crust.

Many uses have been found for lithium and its compounds. Lithium has the highest specific heat of any solid element and is used in heat transfer applications. It is used to make special glasses and ceramics, including the Mount Palomar telescope's 200 inch mirror. Lithium is the lightest known metal and can be alloyed with aluminium, copper, manganese, and cadmium to make strong, lightweight metals for aircraft. Lithium hydroxide (LiOH) is used to remove carbon dioxide from the atmosphere of spacecraft. Lithium stearate (LiC₁₈H₃₅O₂) is used as a general purpose and high temperature lubricant. Lithium carbonate (Li₂CO₃) is used as a drug to treat manic depression disorder.

CHEMISTRY - PERIODIC TABLE - ALKALI METALS #6

ALKALI METALS

Alkali Metals to the Left

Let's go to the left side of the periodic table. When looking for families, the first one you will find is the alkali metal family of elements. They are also known as the alkaline metals. 
You should remember that there is a separate group called the alkaline earth metals in Group Two. They are a very different family, even though they have a similar name. That far left column is Group One (Group I). When we talk about the groups of the periodic table, scientists use Roman numerals when they write them out. The "one" in this case refers to having one electron in the outermost orbital. 

A Family Portrait

Who's in the family? Starting at the top we find hydrogen (H). But wait. That element is NOT in the family. When we told you about families, we said that they were groups of elements that react in similar ways. Hydrogen is a very special element of the periodic table and doesn't belong to any family. While hydrogen sits in Group I, it is NOT an alkali metal. 

Family Bonding

Now that we've covered that exception, the members of the family include:

• lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr). As with all families, these elements share traits. They are very reactive. Why? They all have one electrons in their outer shell. That's one electron away from being happy (full shells). When you are that close to having a full shell, you want to bond with other elements and lose that electron. An increased desire to bond means you are more reactive. In fact, when you put some of these pure elements in water (H₂O), they can cause huge explosions. 

• The alkali metals are also metals. That seems obvious from the name. Often, in chemistry, characteristics are assigned by the way elements look. 
• You will find that the alkali group is shiny and light in weight. Their light weight and physical properties separate them from other metals. 
• They are malleable (bendable) and sometimes soft enough to be cut with a dull knife. 
• Alkali metals are not the type of metals you would use for coins or houses. 

PUZZLE PRACTICE

CHEMISTRY - PERIODIC TABLE - METALS #5

Metal Basics

We wanted to give you a big overview of metals before we get into details about specific families. 
Almost 75% of all elements are classified as metals. 

They are not all like silver (Ag), gold (Au), or platinum (Pt). Those are the very cool and shiny ones. There are other metals like potassium (K) and iridium (Ir) that you might not think about right away. 

Many Kinds of Metals

How many kinds of metals are there? So many. Don't even try to memorize them all. Just remember the ones you might need in class. 
Here's a quick list: 

• Actinide Metals, Lanthanide Metals, Alkali Metals, Alkaline-Earth Metals, Rare Metals, Rare-Earth Metals, and Transition Metals. 
• Remember, that's the easy list. Lucky for you, the periodic table is excellent at organizing elements, and you will find each of these groups in specific areas of the periodic table. 

How Do You Identify a Metal?

What are the characteristics of metals? We've got four traits that will help you identify whether an element is a metal or not: 

1. Conduction: Metals are good at conducting electricity. Silver (Ag) and copper (Cu) are some of the most efficient metals and are often used in electronics. 

2. Reactivity: Metals are very reactive, some more than others, but most form compounds with other elements quite easily. Sodium (Na) and potassium (K) are some of the most reactive metals. A metal like iron (Fe) forms iron oxide (Fe₂O₃), which you know as rust. 

3. Chemical: It gets a little complex here. Metals usually make positive ions when the compounds are dissolved in solution. Also, their metallic oxides make hydroxides (bases) (OH^-), and not acids, when in solution. Think about this example: When sodium chloride (NaCl) is dissolved in water (H₂O), it breaks apart into sodium (Na+) and chlorine (Cl^-) ions. Do you see how that sodium is the positive ion? Sodium is the metal. It works that way for other metals. Potassium chlorine (KCl) works the same way. When it is dissolved, the potassium ion (K⁺) is the positive ion. 

4. Alloys: Metals are easily combined. Mixtures of many metallic elements are called alloys. Examples of alloys are steel and bronze.