Trends in Period 3 Elements

Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor)

Reactions of Period 3 Elements

Only three period 3 elements will react with water; sodium, magnesium and chlorine. Below are the reactions of sodium and magnesium with water. Sodium reacts quite vigorously with cold water. But for the reaction with magnesium to occur, steam must be used.

Was this helpful? Yes | No | I need help

2Na (s) + 2H2O (l) ==>> 2NaOH (aq) + H2 (g) Mg (s) + H2O (g) ==>> MgO (s) + H2 (g)

Now we will look at the reactions of period 3 elements with oxygen. The reactions and some notes on them are in the table below.

the reaction of period 3 elements with oxygen

All period 3 elements up to phosphorous will react with chlorine, these reactions and some notes on them are in the table below.

the reaction of period 3 elements with chlorine

Acid-Base Properties of Oxides

Those oxides that are produced in the reactions above have various physical properties. Sodium and magnesium oxides have ionic structures and silicon, phosphorous and sulphur oxides have covalent bonding. Aluminium oxide on the other hand, has a type of boding that is somewhere in between. Since aluminium has a very high charge density it is able to distort the electron cloud so that aluminium oxide has a very covalent character.

Was this helpful? Yes | No | I need help

In the table below are the reactions of period 3 oxides with water, with the resulting pH.

the reactions of period 3 oxides with water and pH

You will notice that the trend in the pH of the solutions formed goes from alkaline to acidic. This is because the less electronegative sodium has a weak Na-O bond and the oxygen is more easily given up to react with H+. Further along though, a strong S-O bond keeps this together and more H+ is generated. The amphoteric aluminium oxide has a bonding which is both ionic and covalent in nature.

Was this helpful? Yes | No | I need help

When these oxides are reacted with acids or bases, a neutralization occurs with a salt and water produced. Aluminium oxide is amphoteric, meaning it reacts with both acids and bases.

Reactions of Chlorides with Water

When period 3 elements are reacted with chlorine gas the chlorides X-Cl1-5 are produced in the order Na, Mg, Al, Si, and P. The sodium and magnesium chlorides are ionic structures which have high boiling points. Aluminium chloride will sublimate and the Si and P chlorides are both liquids at room temperature.

Was this helpful? Yes | No | I need help

Below are the reactions of the period 3 chlorides with water, along with the pH values.

the reaction of period 3 chloridess with water.

The covalent chlorides (aluminum, silicon, phosphorous) are hydrolysed by water and form acidic solutions that contain HCl. Whereas the ionic chlorides of sodium and magnesium simply dissolve.


ScienceAid welcomes all comments. If you do not want to be anonymous, register or log in. It is free.

Featured Author
166 Articles Started
1,270 Article Edits
43,065 Points
Jamie is a featured author with ScienceAid. Jamie has achieved the level of "Captain" with 43,065 points. Jamie has started 166 articles (including this one) and has also made 1,270 article edits. 42,500 people have read Jamie's article contributions.
Jamie's Message Board
Jamie: Hi, my name is Jamie.
Jamie: Can I help you with your problem about "Trends in Period 3 Elements"?

Article Info

Categories : Inorganic

Recent edits by: Jamie (ScienceAid Editor)

Share this Article:

Thanks to all authors for creating a page that has been read 522 times.

Do you have a question not answered in this article?
Click here to ask one of the writers of this article

Thank Our Volunteer Authors.

Would you like to give back to the community by fixing a spelling mistake? Yes | No