how many groups and periods are there in the long form periodic table? how are these numbered?
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Answer:
There are seven periods in 18 groups
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Chemistry > Classification of Elements and Periodicity in Properties > Modern Periodic Table
Classification of Elements and Periodicity in Properties
Modern Periodic Table
Why are certain elements grouped together in the modern periodic table of elements? For example, we can find Helium and Argon grouped together as inert gases. Also, what is the basis of grouping elements in the periodic table? Let us find out. First, we will understand the basis for organizing elements. And then, we will learn about the characteristics of the modern periodic table.
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Why do elements in the same group have similar physical and chemical properties?
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Use the periodic table to answer the following questions.
(a) Identify an element with five electrons in the outer subshell.
(b) Identify an element that would tend to lose two electrons.
(c) Identify and element that would tend to gain two electrons.
(d) Identify the group having metal non-metal liquid as well as gas at the room
temperature.
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Which of the following statements related to the modern periodic table is incorrect?
(a) The p-block has 6 columns because a maximum of 6 electrons can occupy all
the orbitals in a p-shell
(b) The d-block has 8 columns because a maximum of 8 electrons can occupy all the orbitals in a d-subshell
(c) Each block contains a number of columns equal to the number of electrons that can occupy that subshell
(d) The block indicates value of azimuthal quantum number (I) for the last subshell that received electrons in building up the electronic configuration
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Modern Periodic Law
The modern periodic law states that the physical and chemical properties of the elements are the periodic functions of their atomic numbers.
Scientists arranged elements in increasing order of their atomic numbers from left to right across each row. And discovered that the elements having similar properties repeat after regular intervals.
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Modern Periodic Table
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Why atomic number and not atomic mass?
Atomic mass is the total mass of the protons and neutrons present in a nucleus of an atom. Whereas, the atomic number is the number of protons in a nucleus. Also, the number of protons in the nucleus is equal to the electrons present outside the nucleus.
We know that the nucleus is deep-seated inside an atom. But the electrons outside it, especially the ones in the outermost shell, are free to move around. Hence they take part in chemical reactions. For this reason, the properties of an element depend on the atomic number rather than the atomic mass.
Read about the Historical Development of the Periodic Table.
Long Form of Periodic Table
The modern or long form of the periodic table is based on the modern periodic law. The table is the arrangement of elements in increasing order of their atomic numbers. The modern periodic table is the present form of the periodic table. And it consists of 18 vertical columns and 7 horizontal rows.
Modern Periodic Table of elements
Modern Periodic Table
Groups in the Modern Periodic Table
Groups are the vertical columns in the modern or long form of the periodic table.
There are 18 groups in the periodic table.
These groups are numbered from 1 to 18.
Each group consists of elements having the same outer shell electronic configuration.
Periods in the Modern Periodic Table
Periods are the horizontal rows in the modern or long form of the periodic table.
There are 7 periods in the periodic table.
These are numbered as 1, 2, 3, 4, 5, 6 and 7 from top to bottom.
The 1st period consists of only two elements – Hydrogen and Helium.
While the 2nd and 3rd period consists of 8 elements each.
The 4th and 5th period consists of 18 elements each
On the other hand, the 6th period consists of 32 elements.
The 7th period of the periodic table now has four new elements. They are 113-Nihonium, 115-Moscovium, 117-Tennessine, and 118 –Oganesson. This addition has completed the 7th period with 32 elements.
Also, the long form of the periodic table consists of a separate panel at the bottom. It consists of 14 elements of the 6th period called the lanthanoids. And 14 elements in the 7th period called the actinoids.
Each period represents the number of shells or energy levels present in an atom of an element.