The modern periodic table is developed after the periodic law and a periodic table given by Mendeleev. In the latter part of the 18th century, Mendeleev made his periodic table. Scientists did not know about the internal structure of the atom back then. The development of various atomic models and advances in quantum theory revealed that the atomic number is the most basic property of a chemical element. This led to the modification of Mendeleev’s periodic law, which is today called as modern periodic law. Check ⇒ History of Periodic Table Table of ContentsModern Periodic Law DefinitionThe modern Periodic law can be stated as:
The atomic number is equal to the number of electrons or protons in a neutral atom. After knowing the fundamental unit of elements, scientists now had a clear idea about quantum numbers and electronic configuration of elements in the periodic table. After knowing the periodic law, chemists noticed that there is an analogy between the 94 naturally occurring chemical elements. This analogy made people more curious about the chemistry of these elements. Scientists made various artificial elements. A new periodic table was developed based on the modern periodic law by modifying the Mendeleev’s periodic table. Recommended Videos The Modern Periodic TableThe present form of a periodic table that is widely used across the globe is the long form of the periodic table. In this form of a periodic table, the horizontal rows are called periods and the vertical columns are known as the groups. Groups consist of elements that have similar outer shell electronic configuration in their atoms. Previously the groups were named as IA,…VIIIA, VIII, IB…VIIB and 0. But now they are named as 1, 2, 3…18. In the modern periodic table, periods are the seven horizontal rows. Principle quantum number ‘n’ decides the period of the element. Principle quantum number (n) is one of the four quantum numbers (n, l, m, and s). It tells us about the principle electron shell. For example, if n= 3, then it indicates the principle shell as 3. Classification of the Elements in the Periodic Table:Classification of the elements in the periodic table can be done in four ways on the basis of their electronic configurations: Elements of group 18 of the modern periodic table are considered a noble gas. The electronic configuration of the first element (helium) of this group is 1s2. Rest all the elements (neon, argon, krypton, xenon, and radon) have their outer shell electronic configuration is ns2np6. As the octet of these elements is complete, hence they are highly stable elements. S-lock and P-block elements come under the category of representative elements. Elements in groups 1 and 2 are known as the s – block elements (elements with 1s2and 2s2 outermost configuration). Group 13-17 are known as the p-block elements (outermost configuration varies from ns2np1 to ns2np5). Elements which belong to group 3 to 12 and have their outer shell electronic configuration as (n-1)d1-10ns1-2 are referred to as transition elements. These elements are also known as the d-block elements. Lanthanides and actinides series which fall at the bottom of the periodic table comes under the category of inner transition elements. In these elements the 4f and 5f orbitals are partially filled, rendering them special properties.
In 1869, Dmitri Mendeleev and Lothar Meyer established the periodic law independently. The first periodic table was developed by Mendeleev and soon followed by Meyer. Each grouped the elements by their mass and proposed regularly reoccurring those properties.
Periodic law is recognized as one of chemistry’s most important concepts. While dealing with the chemical elements, their properties, and their chemical reactions, each chemist makes use of Periodic Law, whether consciously or not. The development of the modern periodic table was driven by periodic law.
Periodic trends are common patterns in the periodic table showing us the various aspects of an element such as electronegativity, atomic radius, or ionizing power. The periodic law tells us that when grouped by atomic number, certain properties of elements occur periodically.
Generally, nuclear mass decreases from left to right and always increases from top to bottom. As the atomic number has been developed as the basis for organizing the elements on the periodic table, the atomic number will always increase from left to right and top to bottom.
In a given period, the valence shell electronic configuration of any two elements is not the same. Because of this, elements throughout time have different chemical properties with a periodic gradation from left to right for their physical properties. This is referred to as periodic property. This is just a brief description of the periodic table and the classification of elements. To know more about it, register with BYJU’S & download BYJU’S – the learning app. If you still have doubts regarding the periodic law and would like to learn about periodic table class 10, check out our Introduction to the Periodic Table for detailed clarification.
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As early chemists worked to purify ores and discovered more elements, they realized that various elements could be grouped together by their similar chemical behaviors. One such grouping includes lithium (Li), sodium (Na), and potassium (K): These elements all are shiny, conduct heat and electricity well, and have similar chemical properties. A second grouping includes calcium (Ca), strontium (Sr), and barium (Ba), which also are shiny, good conductors of heat and electricity, and have chemical properties in common. However, the specific properties of these two groupings are notably different from each other. For example: Li, Na, and K are much more reactive than are Ca, Sr, and Ba; Li, Na, and K form compounds with oxygen in a ratio of two of their atoms to one oxygen atom, whereas Ca, Sr, and Ba form compounds with one of their atoms to one oxygen atom. Fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) also exhibit similar properties to each other, but these properties are drastically different from those of any of the elements above. Dimitri Mendeleev in Russia (1869) and Lothar Meyer in Germany (1870) independently recognized that there was a periodic relationship among the properties of the elements known at that time. Both published tables with the elements arranged according to increasing atomic mass. But Mendeleev went one step further than Meyer: He used his table to predict the existence of elements that would have the properties similar to aluminum and silicon, but were yet unknown. The discoveries of gallium (1875) and germanium (1886) provided great support for Mendeleev’s work. Although Mendeleev and Meyer had a long dispute over priority, Mendeleev’s contributions to the development of the periodic table are now more widely recognized (Figure 1). Figure 1. (a) Dimitri Mendeleev is widely credited with creating (b) the first periodic table of the elements. (credit a: modification of work by Serge Lachinov; credit b: modification of work by “Den fjättrade ankan”/Wikimedia Commons) You can view the transcript for “The Periodic Table: Crash Course Chemistry #4” here (opens in new window). By the twentieth century, it became apparent that the periodic relationship involved atomic numbers rather than atomic masses. The modern statement of this relationship, the periodic law, is as follows: the properties of the elements are periodic functions of their atomic numbers. A modern periodic table arranges the elements in increasing order of their atomic numbers and groups atoms with similar properties in the same vertical column (Figure 2). Each box represents an element and contains its atomic number, symbol, average atomic mass, and (sometimes) name. The elements are arranged in seven horizontal rows, called periods or series, and 18 vertical columns, called groups. Groups are labeled at the top of each column. In the United States, the labels traditionally were Roman numerals with capital letters. However, IUPAC recommends that the numbers 1 through 18 be used, and these labels are more common. For the table to fit on a single page, parts of two of the rows, a total of 14 columns, are usually written below the main body of the table. Figure 2. Elements in the periodic table are organized according to their properties. Many elements differ dramatically in their chemical and physical properties, but some elements are similar in their behaviors. For example, many elements appear shiny, are malleable (able to be deformed without breaking) and ductile (can be drawn into wires), and conduct heat and electricity well. Other elements are not shiny, malleable, or ductile, and are poor conductors of heat and electricity. We can sort the elements into large classes with common properties: metals (elements that are shiny, malleable, good conductors of heat and electricity—shaded yellow); nonmetals (elements that appear dull, poor conductors of heat and electricity—shaded green); and metalloids (elements that conduct heat and electricity moderately well, and possess some properties of metals and some properties of nonmetals—shaded purple). The elements can also be classified into the main-group elements (or representative elements) in the columns labeled 1, 2, and 13–18; the transition metals in the columns labeled 3–12; and inner transition metals in the two rows at the bottom of the table (the top-row elements are called lanthanides and the bottom-row elements are actinides; Figure 3). The elements can be subdivided further by more specific properties, such as the composition of the compounds they form. For example, the elements in group 1 (the first column) form compounds that consist of one atom of the element and one atom of hydrogen. These elements (except hydrogen) are known as alkali metals, and they all have similar chemical properties. The elements in group 2 (the second column) form compounds consisting of one atom of the element and two atoms of hydrogen: These are called alkaline earth metals, with similar properties among members of that group. Other groups with specific names are the pnictogens (group 15), chalcogens (group 16), halogens (group 17), and the noble gases (group 18, also known as inert gases). The groups can also be referred to by the first element of the group: For example, the chalcogens can be called the oxygen group or oxygen family. Hydrogen is a unique, nonmetallic element with properties similar to both group 1 and group 17 elements. For that reason, hydrogen may be shown at the top of both groups, or by itself. Figure 3. The periodic table organizes elements with similar properties into groups. Click on this link to the Royal Society of Chemistry for an interactive periodic table, which you can use to explore the properties of the elements (includes podcasts and videos of each element). You may also want to try this one from PeriodicTable.com that shows photos of all the elements.
Atoms of each of the following elements are essential for life. Give the group name for the following elements:
Check Your LearningGive the group name for each of the following elements:
In studying the periodic table, you might have noticed something about the atomic masses of some of the elements. Element 43 (technetium), element 61 (promethium), and most of the elements with atomic number 84 (polonium) and higher have their atomic mass given in square brackets. This is done for elements that consist entirely of unstable, radioactive isotopes (you will learn more about radioactivity in the nuclear chemistry module). An average atomic weight cannot be determined for these elements because their radioisotopes may vary significantly in relative abundance, depending on the source, or may not even exist in nature. The number in square brackets is the atomic mass number (and approximate atomic mass) of the most stable isotope of that element.
The discovery of the periodic recurrence of similar properties among the elements led to the formulation of the periodic table, in which the elements are arranged in order of increasing atomic number in rows known as periods and columns known as groups. Elements in the same group of the periodic table have similar chemical properties. Elements can be classified as metals, metalloids, and nonmetals, or as a main-group elements, transition metals, and inner transition metals. Groups are numbered 1–18 from left to right. The elements in group 1 are known as the alkali metals; those in group 2 are the alkaline earth metals; those in 15 are the pnictogens; those in 16 are the chalcogens; those in 17 are the halogens; and those in 18 are the noble gases.
Glossaryactinide: inner transition metal in the bottom of the bottom two rows of the periodic table alkali metal: element in group 1 alkaline earth metal: element in group 2 chalcogen: element in group 16 group: vertical column of the periodic table halogen: element in group 17 inert gas: (also, noble gas) element in group 18 inner transition metal: (also, lanthanide or actinide) element in the bottom two rows; if in the first row, also called lanthanide, of if in the second row, also called actinide lanthanide: inner transition metal in the top of the bottom two rows of the periodic table main-group element: (also, representative element) element in columns 1, 2, and 12–18 metal: element that is shiny, malleable, good conductor of heat and electricity metalloid: element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals noble gas: (also, inert gas) element in group 18 nonmetal: element that appears dull, poor conductor of heat and electricity period: (also, series) horizontal row of the period table periodic law: properties of the elements are periodic function of their atomic numbers. periodic table: table of the elements that places elements with similar chemical properties close together pnictogen: element in group 15 representative element: (also, main-group element) element in columns 1, 2, and 12–18 series: (also, period) horizontal row of the period table transition metal: element in columns 3–11 |
A part of modern periodic table is given below on its basis answer the following questions
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