In this video, we will explore more on the Periodic Table, and find out what are the general features and patterns in the Periodic Table.
General
The Periodic Table is a list of elements, arranged in order of increasing proton or atomic number. Elements are divided into Periods and Groups.
A group is a vertical column of elements. There are eight groups of elements, numbered in roman numeral, I, II, III, IV, V, VI, VII, 0. Group 0 is sometimes known as Group VIII.
A Period is a horizontal row of elements. There are seven rows of elements.
The block of metals in the middle of Periodic Table, between Group II and III, are called transition elements, or transition metals.
Metallic to non-metallic character of elements across a period
The elements in a Periodic Table can be classified based on their metallic and non-metallic properties. We can draw a diagonal line in the Periodic Table to divide the metals from non-metals. Metals are on the left, while non-metals are on the right of the diagonal line.
The elements that are near this line are called metalloids. In the Periodic Table shown in this video, the metalloids are coloured orange. The elements include- boron, silicon, germanium, arsenic, antimony, tellurium and polonium.
Metalloids are special, because they have the properties of both metals and non-metals. One common example is Silicon, which is widely used in semi-conductor industry. It is used to make computer chips.
In general, elements with small number of electrons in the outermost shell are metals (Group I and II). Elements with large number of electrons in the outermost shell are non-metals (Group VII and 0).
From left to right, across a period, there is a decrease in metallic properties and an increase in non-metallic properties.
Names of elements in different Groups
Group I: Alkali Metals
Group II: Alkaline Earth Metals
Group VII: Halogens
Group 0: Noble Gases
Between Group II & III: Transition Metals/Transition Elements
Properties of Elements in a Group
Elements in the same Group have the same number of valence electrons and similar chemical properties. They form ions of the same charge, same number of bonds and form compounds of similar formula.
Going down the Group, the proton number increases and atomic size increases.
Properties of elements across a Period
Elements in the same Period have the same number of electron shells.
For example, elements in the third period has three electron shells.
From left to right, across a period, there is a decrease in metallic properties and an increase in non-metallic properties.
The chemical properties of the oxides change from basic oxide to amphoteric oxide to acidic oxide across the Period. The oxides of metals are usually basic, and the oxides of non-metals are usually acidic.
Some oxides of metals are both basic and acidic, we call them amphoteric oxides. The common examples are ZAP- zinc oxide (ZnO), aluminium oxide(Al2O3) and lead(II) oxide (PbO).
Some oxides of non-metals are neutral. The common examples are carbon monoxide (CO), nitrogen monoxide (NO) and water (H2O)
Relationship between Group number and ion formed
Elements in Group I, II & III are metals. They lose electrons to form positive ions. They form ions of +1, +2 and +3 respectively.
Elements in Group VI and VII are non-metals. They gain electrons to form negative ions. They form ions of -2 and -1 respectively.
Elements in Group IV and V tend to share electrons to form covalent compounds.
Elements in 0 have stable noble gas electronic configuration. They do not form compounds.
Topic: The Periodic Table, O Level Chemistry, Singapore
If you would like to know more about Group I elements, check out this post.
If you would like to know more about Group VII elements, check out this post.
Click here if you would like to know more about noble gases and transition elements.
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