Alkali Metals

The Alkali Metals
Lithium #3 Li
Sodium #11 Na
Potassium #19 K
Rubidium #37 Rb
Cesium #55 Cs
Francium #87 Fr

All the alkali metals react with water. As you go down the list, the elements become more and more reactive. Here is a cool Quicktime movie showing potassium reacting with water. [Note: if you can't get it to work, be sure to install (or reinstall) Quicktime on your computer - it's free. Here's the download link for Quicktime.]

All the alkali metals are very light and some can float on water. They are soft, and can be cut with a knife. They have low melting points: some can be melted with body temperature!

These metals are incredibly reactive, and are not the types of metals you would use to make metal objects.

All the alkali metals have only one electron in their outer valence shell. They easily lose this electron and gain a positve (+1) charge. Having a positive charge, they react with any negatively charged ion or molecule, such as Cl-, Fl-, OH- (hydroxide), or CO3^2- (carbonate). Hydroxide compounds are caustic and can burn. Because they are so often associated with the alkali metals these compounds are sometimes described as being "alkaline".

The world "alkali" comes from the Arabic "al qali", meaning "from ashes", because two highly important alkali metals, sodium and potassium, came from ashes. Fireplace ashes are mostly potassium carbonate.

2. Lithium is the lightest metal of the group known in the periodic table as what? the alkali metals? Alkali metals

9. Lithium is used as a medicine to treat what mental disorder? bipolor or manic depression

10. Lithium can absorb large amounts of heat with only a slight increase in its own temperature and has the highest heat capacity of any of the elements. Scientists therefore use lithium to absorb the heat from what type of reaction? nuclear.

1. True or false: Sodium metal is light enough to float on water and soft enough to cut with a knife. True!

6. What common word was derived from the Latin "sal" for "salt" because Roman soldiers were sometimes paid their wages in salt. Salary

7. Name a strong sodium base (opposite of acid) that is sometimes called lye or caustic soda and serves as a drain cleaner or oven cleaner. sodium hydroxide (NaOH)

8. Soap is a mixture of sodium hydroxide and what? fat (does this explain why our rats like to eat soap?)

9. What is the chemical name for soda ash, which is mixed with sand and lime to make glass? sodium carbonate (NaCO₃)

12. Sodium vapor lamps give off a lot of light for a small amount of electricity used, and are commonly used where? highways

Remember the alkali metals lithium and sodium? Like potassium, they are soft, light metals that react with water. But the reaction becomes more dramatic (and dangerous) as you go down the column of alkali metals. So potassium is more reactive than both lithium and sodium. the reaction between potassium metal and water

the reaction between potassium metal and water

Remember that the alkali metals have one extra electron and therefore react strongly with atoms or molecules that need electrons to fill their outer shells. In solutions, alkali metals lose an electron and have a positive (+1) charge. They are then called cat-ions (eg. Na+, Li+ and K+) and react readily with an-ions like fluoride and chloride (Fl-, Cl-).

"K" is for potassium?
Where the heck does the "K" come from (the chemical abbreviation for potassium)? Potassium has another name, used in much of the world: Kalium. It comes from Arabic "al qali", meaning ashes, which is where potassium came from throughout most of history. Get that? Alkali. And we're talking about the alkali metals.

In Europe, "potash" was obtained from the ashes of plant material. The ashes were leached and the solution was evaporated to dryness, an operation at one time carried out in iron pot. Hence: "Pot-ash". The mysterious element derived from potash was called "potash-ium" or potassium.

High pH - alkalis (bases)
Potash solutions were alkaline because potassium-hydroxide (KOH) was formed. People usually called it lye (both KOH and NaOH were called lye). Lye was mixed with fat to make soap.

Early settlers used cave spring water to leach saltpeter—used in gunpowder, preservatives and fertilizers—from guano (bat droppings) deposits found in caves.

Saltpeter (saltpetra or "rock salt") is potassium nitrate, KNO3. Back in the old days, it was used for fertilizer, preservative (oh, yummmm.....), and to make gunpowder. It's hard to believe it was added to food when you consider that it was made from animal feces. No wonder it preserved the food! A lot of saltpeter was dug out of old caves in places like Kentucky and Tennessee, where the bat droppings from thousands of years had made piles many feet thick.

I would like to know what person sat around thinking up ideas like, "Let's run some water through bat poop and put it in our pickled pigs feet to make them taste good!"

Gunpowder. This is where the boys get interested. Gunpowder is made from saltpeter, sulfur and charcoal. If you want to read more about that, check out this Caveman Chemistry webpage.

1. Potassium nitrate, derived from animal droppings, is known as what? saltpeter

5. Which do plant remove from the soil and water, potassium or sodium? potassium

6. Almost all of the potassium chloride mined today is used for what? fertilizer

8. Potassium and other alkali metals react violently with water to create what flammable gas? hydrogen

9. Potassium and other alkali metals are stored in a liquid such as what? kerosene or naptha (either one)

10.Saltpeter, or saltpetra, literally means what? salt rock - (because it looks and tastes like halite, or rock-salt)

11. When gunpowder is heated, large volumes of carbon dioxide and nitrogen gas are created. The sudden expansion of these gases causes what? an explosion

12. Potassium hydroxide (lye) was once created by passing rainwater through fireplace ashes, collecting the liquid, and boiling it down. Is potassium hydroxide an acid or a base/alkali? A base

14. Each person has about how much potassium in their body? 140 grams (that's about how much the tuna in a can of tuna fish weighs).

15. What potassium isotope causes much of our natural radiation exposure and has a half-life of 1.25 billion years? potassium-40

Of the three new elements listed here, only cesium is of any real importance. The cesium in this vacuum tube (photo) can be melted by holding the tube in your hand: Body temperature is higher than the melting point of cesium! Only mercury has a lower melting point.

Cesium-133 is the world's official measure of time. The second is now defined as the time it takes for exactly 9,192,631,770 vibrations of the radiation emitted by an excited cesium-133 atom. Isn't that just weird? Here's a better explanation. It gets even weirder if you look at how they measure this now. Here's a page that explains it and has a video on how it works. It all looks like voodoo to me but apparently it works. Don't worry, I don't expect you to know all that stuff. Just be familiar with the idea that our clocks are based on the vibrations of cesium-133 radiation and that there are over 9 billion cesium-133 radiation vibrations in just one second.

Rubidium and cesium were named after the color of their "spectral lines". What the heck are those, you ask? Well, here is a very brief answer.

1. This alkali metal is named for the Latin "coesius", which means "sky blue", because of its spectral emission lines. Cesium.

3. Which alkali metal has the lowest melting point, and can be melted by body temperature? cesium

4. Which alkali metal is named after the Latin "rubidus", meaning "deep red" (as in ruby!), because of its spectral lines? rubidium

5. To get spectral lines of an element, scientists heat up an element until it glows, and then direct the light from the glowing element through a what? prism

7. Because this alkali metal is so radioactive and has such a short half-life, the Earth's crust probably contains less than one once of it. Francium.

8. Cesium, potassium and rubidium react with oxygen to form "superoxides" that release what when they react with water or carbon dioxide. oxygen (used by emergency workers in self-contained breathing apparatuses).

9. This element is named after France, and is the most useless of all the alkali metals. Francium.