Class 10th Ch-5 Ncert Notes Science Periodic Table & classification, This is the Comprehensive and brief summary of this chapter.
If you want the best and the Detailed Notes of this chapter. Then There are 2 Parts that I have created for you. Just click here to check out those two parts. Part-1 ( Ch-5 [Periodic Table and Its classification] Chapter Detailed Notes), Part-2 ( Ch-5 [Periodic Table and Its classification] Chapter Detailed Notes).
Here Our Chapter Starts:- Table of Content Present below will help you More About this content.
Class 10th Ch-5 Ncert Notes Science Periodic Table & classification
- Matter around us is present in the form of elements, compounds, and mixtures.
- Elements are substances containing atoms only one type. Example:- Na, Mg, Au, etc:-
- There are 118 elements known to us. All of these have different properties.
Need for periodic classification of elements:-
- To make the study of these elements easy, these elements have been divided into few groups in such a way that element in the same group have similar properties. Now a study of a large number of 9of elements is reduced to a few groups of elements.
- Drobereiner’s Triads:- When elements were arranged in the order of increasing atomic masses, groups of three elements (Known as triads). having similar chemical properties are obtained.
The Atomic mass of the middle element of the triad was roughly the average of atomic, masses of the other two elements.
Limitations: Only three triads were recognized from the elements known at that time.
Li, An, K….. Ca,Sr,Ba…. Cl, Br, I…
Newland’s law of octaves:-
Newland arranged the known elements in the order of Increasing atomic masses and found that the properties of every 8th element are similar to that of the 1st element.
He compared this to octaves found in music are called the ‘Law of Octaves’.
For Example:- The Properties of Lithium (Li) and Sodium (Na) were found to be the same.
Limitations of Newland’s Law of Octaves:-
- It was applicable to up to Calcium (For lighter elements),
- Properties of newly discovered elements did not fit into the law of Octave.
- To fit elements into the table, Newlands put even two elements together in one slot and that too in the column of unlike elements having very different properties.
Mendeleev’s Periodic table:-
As I said you that this is not the Detailed Notes of this Chapter. Click here to check the detailed Notes of this Chapter.
When elements arranged in the order of increasing atomic masses, the elements with similar properties occur at regular intervals. The properties of elements are periodic functions of their atomic masses.
Mendeleev’s periodic table is based on the chemical properties of the elements. It contains 6 periods (Horizontal rows) and 8 Groups (Vertical columns).
Modern Periodic Table:-
- An atomic number of an element is a more fundamental property than its atomic masses.
- According to the modern periodic law: The properties of elements are a periodic function of their atomic number.
- All the anomalies o Mendeleev’s classifications disappear.
Merits of Mendeleev’s periodic table:-
- Some gaps were left for the Undiscovered elements like gallium, scandium, and germanium.
- Predict the properties of the element on the basis of their position in the periodic table.
- Accommodate noble gases when they were discovered without distributing the original arrangement.
Limitations of Mendeleev’s Classifications:-
- The position of Isotopes could not be explained.
- No fixed position for hydrogen.
- The wrong order of atomic masses of some elements could not be explained.
Explanation of Anomalies:-
(i). The explanation for the position of isotopes (Same atomic number put at one place in the same group).
(ii). Cobalt with atomic number 27 came first and Nickel (28) should come later.
(iii). Unlike atomic masses, an atomic number is always a whole number, So there is no element between hydrogen and helium.
- Atomic number:- It is denoted by Z and equal to the no. of protons in the nucleus of an atom.
- The modern periodic table has 18 vertical columns known as groups and 7 horizontal known as Periods.
- Elements with the same number of valance electrons are placed in the same group. For Example, Li: 2,1… Na: 2,8,1…k: 2,8,8,1
- Outermost of valance electrons in all the three contain 1 electron. These elements have been placed in the same group.
No shells increases if we go down the group.
Elements with the same number of occupied shells are placed in the period. For Example, Li (2,1): Be(): B(): C(): N():. These elements have the same number of shells (two).
Each period marks a new electronic configuration shell getting files.
The number of elements placed in a particular period depends upon the fact of how electrons are filled into the various shells.
A maximum number of electrons that can be filled in a shell is given by 2n2, Where n is a shell no.
Eg:- K shell n= 1 or 2n2 = 2(1) 2 =8
The position of an element in the periodic table tells us its chemical reactivity.
Valence electrons determine the kind and number of bonds formed by the elements.
Trends in the Modern Periodic Table:
Valency:- No. of valence electrons present in the outermost shell of its atom.
On moving from left to right in each period, the valency of elements increases from 1 to 4 and then decreases to 0.
Valency remains the same down the group.
Atomic Size:- Atomic size refer to the radius of an atom. It may be visualized as the distance between the center of the nucleus and the outermost shell.
Atomic size or radius of an atom decreases as we move from left to right in a period because due to large +ve charge on the nucleus, The electrons are pulled in more closely to the nucleus and size decreases. E.g.
Atomic size increases as we move down the group because new shells are being added and thi9s increase the distance between the nucleus and outermost shell.
Metallic character means the tendency of an atom to the electron.
Metals occupy the left-hand side of the periodic table.
On moving left to right in the period, The metallic character of an element decreases because of the effective nuclear charge increases. It means the tendency to lose electron decreases.
Metals are electropositive as thet=y tens to lose electrons while formed bonds.
Metallic character increases as we go down the group as the effective nuclear charges are decreasing.
- Non-Metal are electronegative as they tend to form bonds by gaining electrons.
- Non-Metals occupies the right side of the periodic table.
- Non-metallic characters increase across a period because due to increase effective nuclear that means the tendency to gain electron increase.
- Non-Effective characters decrease as we move down a group due to a decrease in effective nuclear charge experienced by the valence electrons taus the tendency to gain electron decreases.
- In the middle of the periodic table, we have semic conductor or metalloid because they exhibit some properties of metals and non-metals.
- Oxides of metals are basic in nature while oxides of non-metallic are acids in nature.
If you have any doubts related to this chapter then feel free to ask me in the comment section. I will try to solve your problems as soon as possible.
Also, Don’t forget to share this with all other friends so that we can reach more and more students and provide more and more useful content to the students.
Also if you haven’t followed us on the different Social Media Platforms then please join us there as well, we have a proper team that will help you in solving all of your Queries.
Follow us on Different Social Media Platforms:-