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Properties & Uses of Compounds of Group 1 Elements

Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

Group 1 elements are very reactive. In this lesson we will learn what types of compounds the group forms, how these compounds are formed, and what these compounds are used for.

Group 1 Elements

Have you recently used detergent to wash your clothes? Or baked a batch of cookies? If you've done either of these things, then you have probably used compounds formed from group 1 elements.

Recall that group 1 elements are very reactive. Since they only have one valence electron, they can give up that electron and become like a noble gas in the cation state. So they readily give up that one valence electron.

This means that group 1 elements can readily form compounds like sodium hydroxide, sodium carbonate, sodium bicarbonate, and sodium thiosulphate.

Sodium Hydroxide

Sodium hydroxide, or NaOH, is a very common base. It is also known as lye. When sodium reacts with water sodium, hydroxide is formed. This is often done by making a salt brine, which is done by mixing NaCl (typical table salt) with water. This brine then has an electric current go through it to break apart the ions, in a process called electrolysis. The sodium then combines with the OH from the water and sodium hydroxide is formed.

The reaction process to form sodium hydroxide
Sodium hydroxide reaction

Sodium hydroxide can be used as an oven cleaner, in soaps, and to make paper. It is a very strong base. Since sodium is willing to ionize into just sodium as a cation (because it is like a noble gas), the sodium and hydroxide will often ionize. The hydroxide (OH) then really needs another hydrogen, to make water. It can therefore easily take a hydrogen off of other compounds.

Sodium Carbonate and Bicarbonate

Sodium bicarbonate, or baking soda, has the chemical formula of NaHCO3. When you produce baking soda, sodium carbonate, or soda ash (Na2CO3), can be produced as well. Baking soda is commonly used in baking and in antacids, and is non-toxic. But its counter-part, sodium carbonate, is toxic. It can be found in several cleaning products, but needs to be used with care.

The structure of sodium bicarbonate
Sodium bicarbonate structure

In order to produce sodium bicarbonate and sodium carbonate, salt (NaCl) is combined with carbon dioxide (CO2), water (H2O), and ammonia (NH3). The salt quickly ionizes in the water, forming free sodium cations. The water also ionizes into OH anions (hydroxide) and hydrogen cations. The hydroxide and the carbon dioxide can combine to form the bicarbonate (HCO3). The bicarbonate has a negative charge, so it can interact with the positive charge on the sodium. Only an ionic bond (a bond with weaker strength) is formed, instead of a covalent bond.

The structure of sodium carbonate
Sodium carbonate structure

Under high heat the hydrogen can be taken off of the oxygen so that there is a second negative charge. This allows a second ionic bond to form with another sodium cation to make sodium carbonate.

Since ionic bonds are formed in both instances, both of these compounds are highly basic. If the sodium dissociates from the compound, then the oxygen has a free negative charge to remove a hydrogen from compounds.

Sodium Thiosulphate

Sodium thiosulphate has the chemical formula of Na2S2O3. It has been used to develop photographs, to extract gold, and for medical purposes, such as to treat cyanide poisoning.

The structure of sodium thiosulphate can be confusing when we first look at it. First off, there seems to be too many bonds coming from the center sulfur. Second, there are a bunch of dotted lines, so how do we know where the double bonds are?

Well, there are always two double bonds because there is always a negative two charge (so two of the double bonds are there and two are not at any given moment). The dotted lines mean that these doubles bonds can be between any two of the compounds at any given moment. It changes from one compound to another. This process is called resonance.

The structure of sodium thiosulphate
Sodium thiosulfate structure

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