In chemistry, it is important to keep in mind of the structure of the periodic table and the difference between the elements we know. The idea of grouping these elements are organised according to their physical and chemical properties. Here, you will read about these properties, how to classify elements through a periodic table, and learn about properties of an important group: the alkali metals.

 

First we have to know the distinction in physical properties between METALS and NON-METALS.

METALS

 

Physical

- shiny

- solid at room temperature except for Hg (mercury)

- malleable (they can be bent and pressed into different shapes)

- ductile (they can be drawn into wires. Metals are malleable and ductile because the layers of atoms can slide over each other without the metallic bonds breaking since the electrons are free to move.)

- opaque (not see through) as a thin sheet

- good conductors of heat and electricity

 

Chemical

- left side of the periodic table

- high melting point

- high boiling point

- can form oxides that are alkali

- usually have one to three electrons in their outer shell

- lose their valence electrons easily

 

NON-METALS

Physical

- brittle as a solid

- not ductile

- not shiny

- transparent as a thin sheet

- solid liquid or gas at room temperature

 

Chemical

- usually have four to eight valence electrons

- gain valence electrons easily

- form oxides that are acidic

- poor conductors of heat and electricity

 

Next, it is important to know that elements are arranged into groups with other elements with similar properties. This is done in the periodic table. Click here for a link to an interactive periodic table, with much information on each individual element. In the periodic table the elements into periods (rows), and groups (columns). The group number of an element will tell you the number of valence electrons, while the period number will tell you the number of shells.

 

One significant example of a trend in the periodic table is the alkali metals. Alkali metals are in group one of the periodic table and the first three elements are considered to be safe enough to keep in the school lab. They share a number of properties.

 

Physical properties

Alkali metals are not typical metals

-They are good conductors of heat and electricity

-They are softer than most other metals

-They are lighter than most metals and have a low density

-They have a low melting and boiling points in comparison with most metals.

Chemical properties

Alkali metals are the most reactive of all metals. The reactivity also increases as you go down the column, as shown by this video. Some of the main reactions are:

1.    Reaction with water

-Alkali metals react violently with water, releasing hydrogen and a forming hydroxide. The hydroxide gives alkaline solutions.

An example equation of a reaction between sodium and water is presented as:

sodium + water -> sodium hydroxide + hydrogen

-As the reactivity increases, the reaction starts to vary:

    Lithium floats and fizzes

    Sodium shoots across the water

    Potassium melts with the heat of the reaction and the hydrogen catches fire.

2.    Reaction with non-metals

-When a heated alkali is put into chlorine gas, they will burst into flame and they burn brightly, giving white solids called chlorides. This reaction is shown in the word equation:

sodium + chlorine -> sodium chloride

Sodium chloride is also known as common salt

-When a heated alkali is combined with oxygen, it will also burst into flame, but will burn even more fiercely forming white solids called oxides. The flames turn into different colors:

    For Lithium, the flame is red

    Sodium, the flame is yellow

    Potassium, the flame is lilac

3.    Ionic compounds

A compound formed in these reactions is always ionic. They form ionic compounds in which the metal ion has a charge of 1+. The compounds are white solids that dissolve in water to form colorless solutions.

 

And now for something completely different.....a chemistry cartoon!