The periodic table is one of the most important and basic topics of chemistry. It talks about all the elements present in nature and their atomic masses etc. The elements in the periodic table are arranged in rows and columns. Wherein rows are called ‘periods’ and columns are called ‘groups’. The elements are arranged from left to right in the increasing order of their atomic numbers (numbers of protons in the nuclei of their atoms). The elements are also grouped together in groups according to their properties.
The periodic table is divided as follows:
Based on the properties of elements, the periodic table is divided into metals, nonmetals, and metalloids. There more metallic elements than nonmetallic elements in number. The elements that have properties of both metals and nonmetals combined are placed on the border line between the metals and nonmetals and are called metalloids or semimetals.
Metals in the periodic table completely occupy groups 1 to 12, while they are also present in other groups. They are good conductors of heat, malleable, ductile and shiny to look at. .Most of the metals have 1 or 2 electrons in the outermost energy level, while transition metals also have incomplete inner orbitals. Metals are classified as Alkali metals, alkali earth metals, transition metals and inner transition metals. Due to different electronic configurations, metals have different properties and hence, may not act in the same manner.
Apart from the metals what remains are mostly nonmetals with a few metalloids. They are poor conductors of heat, non-malleable, non-ductile and not shiny by nature (Except for Iodine). Non-metals generally have 4 or more electrons in the outermost shell. Due to this, they have a tendency to accept electrons and are thus, electronegative by nature.
Group 7A/17 halogens are reactive nonmetals. They are commonly known as colorful term “halogen” which means “salt-former” and compounds containing halogens are called “salts”.
The elements of group 8A that is the 18th group of the periodic table are noble gasses. They are colorless and unreactive. They are also included in the nonmetals.
They have the properties of both metals and nonmetals, therefore, they are called semimetals and are also called metalloids. In the periodic table, there are metals on the left side and non-metals on the right side and in between them are placed the semimetals. They are similar to metals but are not metals. Eg. Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium and Astatine(sometimes).
Based on their electronic configuration the periodic table is divided as follows:
You can identify and categorise elements in the following categories based on the which shell the last electron enters..
S- block elements:
Elements with differentiating electron in the s-orbital are categorised as the s-block elements of the periodic table. The elements of group 1A( alkali metals) and 2A( alkaline earth metals) have 1 and 2 electrons respectively in their outermost energy shell. Hence, the groups of IA and IIA are s block elements.
These elements receive their last electron in their p-orbitals and hence they are categorised as the p-block elements. The atoms of these elements are in groups III A, IV A, VA, VI A, VIIA and zero (except helium). The p orbitals extend from 2p to 7p.
The elements in which the differentiating electron enters the d-orbitals are called d-block elements. These elements lie between s and p block elements in the periodic table, and thus are referred to as Transition metals.. In these elements the s- and p- orbitals of the outermost energy shell are completely filled. But the d-orbitals in the penultimate shell(inner to the outermost) are still vacant. The last electrons in these elements, therefore, enters into the d- orbitals. In the periodic table, these elements are found in groups IIIB, IVB, VB, VIB, VIIB, VIII, IB, and IIB( groups 3-12).
F-block elements have two inner orbitals viz., outermost (n), penultimate(n-1) and antepenultimate(n-2) incomplete. In these F-block elements, the last electron enters the f- orbitals (n-2). The F Block elements are further divided into two series as follows:
Lanthanides or rare earth- They extend from the cerium (At.no 58) to lutetium (At no 71). In these elements, the last electrons enter the 4f orbitals.
(b) Actinides – They are from thorium (At. No. 90) to lawrencium (At. No. 103). In these elements, the last electrons enter the 5f orbitals.
Mnemonics for periodic table:
Here is a mnemonic to remember the entire periodic table easily.
How useful is it in chemistry?
From the periodic table, you can find the following things for any elements.
- Atomic size: Atomic size of the element increases from top to bottom in a group.
- The number of shells: from top to bottom number of shell increases by one for each element.
- The number of Valence electrons: No of valence electron are constant.
- Ionisation potential: I.P decreases from top to bottom.
- Electronegativity: Electronegativity decreases from top to bottom.
- Metallic Character: Metallic character increases down the groups.
Summary of all the trends can be found in the below table:
- Classification of elements into periods and groups is very useful and eases in the study of chemistry.
- Suggestions for further research becomes available.
- Prediction of the new element is possible.
The periodic table helps us calculate the molecular mass of a compound. And more uses of how you can calculate the molecular weight etc using the periodic table
For example water( H2O)
|Atom||Number in molecule||Atomic weight||Total Mass|
Well, the periodic table is vast it isn’t easy to learn everything all at once. But the periodic table for sure can make chemistry easy. Chemistry does not only need knowing the concepts it also requires an equal amount of practice. Embibe provides you with practice and tests that will help your score improve by 29% of your previous score.
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