2a) The Periodic Table

Section 2: Chemistry of the elements a) The Periodic Table 

2.1 understand the terms group and period 

Group = 

• The columns of the periodic table.
•  The number of the group an element is in tells you how many electrons it has in its outer shell (eg. If an electron is in group 3, it has 3 electrons in its outer shell.)
• Elements in the same group have similar chemical properties (same amount of electrons in their outer shell, they will therefore react and bond in similar ways)
• Properties of elements change as you go down a group. 

Period = 

• The rows of the periodic table. 
• The number of the period an element is in tells you how many energy levels (shells) it has. For example, if an element is in period 5 then it has 5 energy levels/ shells.
• Properties of elements change as you go along a period. 

2.2 recall the positions of metals and non-metals in the periodic table 

The elements on the left of the zig-zag are all metals. 

The elements on the right of the zig-zag are all non-metals.

2.3 explain the classification of elements as metals or non-metals on the basis of their electrical conductivity and the acid-base character of their oxides 

Metals: 

• Metals are good conductors of electricity because they allow charge to pass through them easily. (They have delocalised electrons which make it possible for an electrical current to pass through.) 
• Metal oxides are basic, and will therefore neutralise acids. Metal oxides which dissolve will form solutions with a pH higher than 7 (alkalis).

Non-metals 

• Non-metals are poor conductors of electricity because they are held tightly together by very strong covalent bonds, and are not free to move around or pass an electric current. 
• Non-metal oxides are acidic. They dissolve in water to form solutions with a pH of less than 7 (acidic.)

2.4 understand why elements in the same group of the Periodic Table have similar chemical properties 

Elements in the same group of the Periodic Table all have the same number of electrons in their outer shell. (Group number = number of electrons in outer shell.) Therefore, all of the elements in a group will have the same amount of electrons they need to gain/lose in order to become stable, meaning they will all react and bond with other elements very similarly and so have similar chemical properties. 

2.5  understand that the noble gases (Group 0) are a family of inert gases and explain their lack of reactivity in terms of their electronic configurations. 

All of the noble gases have full outer shells of electrons, so they are stable.  Because they are stable, they do not need to react with anything or form a bond, so they are also inert (unreactive). For example, helium is a noble gas that has 2 electrons in its outer shell (it only has one shell) , and is its therefore fully stable and inert.