CHEMISTRY - ELEMENT OF THE DAY - FLUORINE

9

F

Fluorine

18.9984032

Atomic Number: 9

Atomic Weight: 18.9984032

r

Phase at Room Temperature: Gas

Element Classification: Non-metal

Period Number: 2    Group Number: 17    

Group Name: Halogen

What's in a name? From the Latin and French words for flow, fluere.

Say what? Fluorine is pronounced as FLU-eh-reen or as FLU-eh-rin.

History and Uses:

Fluorine is the most reactive of all elements and no chemical substance is capable of freeing fluorine from any of its compounds. For this reason, fluorine does not occur free in nature and was extremely difficult for scientists to isolate. The first recorded use of a fluorine compound dates to around 1670 to a set of instructions for etching glass that called for Bohemian emerald (CaF₂). Chemists attempted to identify the material that was capable of etching glass and George Gore was able to produce a small amount of fluorine through an electrolytic process in 1869. Unknown to Gore, fluorine gas explosively combines with hydrogengas. That is exactly what happened in Gore's experiment when the fluorine gas that formed on one electrode combined with the hydrogen gas that formed on the other electrode. Ferdinand Frederic Henri Moissan, a French chemist, was the first to successfully isolate fluorine in 1886. He did this through the electrolysis of potassium fluoride (KF) and hydrofluoric acid (HF). He also completely isolated the fluorine gas from the hydrogen gas and he built his electrolysis device completely from platinum. His work was so impressive that he was awarded the Nobel Prize for chemistry in 1906. Today, fluorine is still produced through the electrolysis of potassium fluoride and hydrofluoric acid as well as through the electrolysis of molten potassium acid fluoride (KHF₂).

Fluorine is added to city water supplies in the proportion of about one part per million to help prevent tooth decay. Sodium fluoride (NaF), stannous(II) fluoride (SnF₂) and sodium monofluorophosphate (Na₂PO₃F) are all fluorine compounds added to toothpaste, also to help prevent tooth decay. Hydrofluoric acid (HF) is used to etch glass, including most of the glass used in light bulbs. Uranium hexafluoride (UF₆) is used to separate isotopes of uranium. Crystals of calcium fluoride (CaF₂), also known as fluorite and fluorspar, are used to make lenses to focus infrared light. Fluorine joins with carbon to form a class of compounds known as fluorocarbons. Some of these compounds, such as dichlorodifluoromethane (CF₂Cl₂), were widely used in air conditioning and refrigeration systems and in aerosol spray cans, but have been phased out due to the damage they were causing to the earth's ozone layer.

CHEMISTRY - IONS MODULE #5

IONS
Looking at Ions
We've talked about ions before. Now it's time to get down to basics. The atomic number of an element, also called a proton number, tells you the number of protons or positive particles in an atom. 

A normal atom has a neutral charge with equal numbers of positive and negative particles. That means an atom with a neutral charge is one where the number of electrons is equal to the atomic number. Ions are atoms with extra electrons or missing electrons. When you are missing an electron or two, you have a positive charge. When you have an extra electron or two, you have a negative charge. 

What do you do if you are a sodium (Na) atom? 

• You have eleven electrons — one too many to have an entire shell filled. You need to find another element that will take that electron away from you. When you lose that electron, you will you’ll have full shells. Whenever an atom has full shells, we say it is "happy." 

Let's look at chlorine (Cl). 

• Chlorine has seventeen electrons and only needs one more to fill its third shell and be "happy." Chlorine will take your extra sodium electron and leave you with 10 electrons inside of two filled shells. You are now a happy atom too. You are also an ion and missing one electron. That missing electron gives you a positive charge. You are still the element sodium, but you are now a sodium ion (Na⁺). You have one less electron than your atomic number. 

Ion Characteristics
So now you've become a sodium ion. You have ten electrons. That's the same number of electrons as neon (Ne). But you aren't neon. Since you're missing an electron, you aren't really a complete sodium atom either. As an ion you are now something completely new. Your whole goal as an atom was to become a "happy atom" with completely filled electron shells. Now you have those filled shells. You have a lower energy. You lost an electron and you are "happy." So what makes you interesting to other atoms? Now that you have given up the electron, you are quite electrically attractive. Other electrically charged atoms (ions) of the opposite charge (negative) are now looking at you and seeing a good partner to bond with. That's where the chlorine comes in. It's not only chlorine. Almost any ion with a negative charge will be interested in bonding with you. 

Electrovalence

Don't get worried about the big word. Electrovalence is just another word for something that has given up or taken electrons and become an ion. 

If you look at the periodic table, you might notice that elements on the left side usually become positively charged ions (cations) and elements on the right side get a negative charge (anions). That trend means that the left side has a positive valence and the right side has a negative valence. Valence is a measure of how much an atom wants to bond with other atoms. It is also a measure of how many electrons are excited about bonding with other atoms. 

There are two main types of bonding, covalent and electrovalent. You may have heard of the term "ionic bonds." 

• Ionic bonds are electrovalent bonds. They are just groups of charged ions held together by electric forces. Scientists call these groups "ionic agglomerates." When in the presence of other ions, the electrovalent bonds are weaker because of outside electrical forces and attractions. Sodium and chlorine ions alone have a very strong bond, but as soon as you put those ions in a solution with H⁺, OH^-, F^- or Mg⁺⁺ ions, there are charged distractions that break the Na-Cl bond. 

Look at sodium chloride (NaCl) one more time. 

• Salt is a very strong bond when it is sitting on your table. It would be nearly impossible to break those ionic/electrovalent bonds. However, if you put that salt into some water (H₂O), the bonds break very quickly. It happens easily because of the electrical attraction of the water. Now you have sodium (Na⁺) and chlorine (Cl^-) ions floating around the solution. 
• You should remember that ionic bonds are normally strong, but they are very weak in water. 

REVIEW: 
 
An ion is an atom or group of atoms that have a net electrical charge. 

• An ion is formed when electrons or protons are gained or lost by an atom. 
• This is different than a neutral atom that has equal numbers of protons and electrons so there is no net electrical charge.

• A simple ion is made up of only one charged atom with either a positive or negative charge. 
• A complex ion is one with a number of atoms with a net charge that is positive or negative. 
• If an atom or atoms lose electrons or gain protons, the ion has a positive charge. This kind of ion is called a cation.
•  If an atom or atoms gain electrons or lose protons, the ion will have a negative charge. This kind of ion is called an anion. 
• Ions normally are found as neutral groups of cations and anions combined. This means when the cations and anions charges are added up, the total is zero.

How are ions created from neutral atoms? 

• Some such as salt compounds come apart or dissociate in certain solutions. 
• Substances that form ions in solutions are called electrolytes. 
• Those that don't form ions in solutions are called non-electrolytes. 
• Electrolytes conduct electricity.

Ions can also be formed from neutral atoms with radiation. They can also be formed by having a substance heated to high temperatures.

CHEMISTRY - ELECTRONS MODULE #6

Charge It!

Electrons are the negatively charged particles ofatom. Together, all of the electrons of an atom create a negative charge that balances the positive charge of the protons in the atomic nucleus. Electrons are extremely small compared to all of the other parts of the atom. The mass of an electron is almost 1,000 times smaller than the mass of a proton. 

Shells and Shapes

Electrons are found in clouds that surround the nucleus of an atom. Those clouds are specific distances away from the nucleus and are generally organized into shells. Because electrons move so quickly, it is impossible to see where they are at a specific moment in time. After years of experimentation, scientists discovered specific areas where electrons are likely to be found. The overall shape of the shells changes depending on how many electrons an element has. The higher the atomic number, the more shells and electrons an atom will have. The overall shell shape will also be more complex (because of the suborbitals) as you have more electrons. 

Creating Bonds

Electrons play a major role in all chemical bonds. There is one type of bonding called electrovalentbonding (ionic), where an electron from one atom is transferred to another atom. You wind up creating two ions as one atom loses an electron and one gains one. The second type of bonding is called covalent bonding, where electrons are actually shared between two or more atoms in a cloud. Both types of bonds have specific advantages and weaknesses. 

Power Up!

Electrons are very important in the world of electronics. The very small particles can stream through wires and circuits, creating currents of electricity. The electrons move from negatively charged parts to positively charged ones. The negatively charged pieces of any circuit have extra electrons, while the positively charged pieces want more electrons. The electrons then jump from one area to another. When the electrons move, the current can flow through the system.