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In the Class 7 textbook topic titled “Our Pasts-2”, pages 48 and 49 have been excluded. These pages mentioned “Mughal Emperors: Major campaigns and events.” The deletions also affected Biology and Chemistry textbooks as the theory of evolution and the periodic table were also purged from class 10 NCERT textbooks. [34] [35]
Those who wish to adopt the textbooks are required to send a request to NCERT, upon which soft copies of the books are received. The material is press-ready and may be printed by paying a 5% royalty, and by acknowledging NCERT. [11] The textbooks are in color-print and are among the least expensive books in Indian book stores. [11]
Xenon reversibly complexes gaseous M(CO) 5, where M=Cr, Mo, or W. p-block metals also bind noble gases: XeBeO has been observed spectroscopically and both XeBeS and FXeBO are predicted stable. [27] The compound Xe 2 Sb 2 F 11 contains a Xe–Xe bond, the longest element-element bond known (308.71 pm = 3.0871 Å). [28]
The p orbital can hold a maximum of six electrons, hence there are six columns in the p-block. Elements in column 13, the first column of the p-block, have one p-orbital electron. Elements in column 14, the second column of the p-block, have two p-orbital electrons. The trend continues this way until column 18, which has six p-orbital electrons.
The inert-pair effect is the tendency of the two electrons in the outermost atomic s-orbital to remain unshared in compounds of post-transition metals.The term inert-pair effect is often used in relation to the increasing stability of oxidation states that are two less than the group valency for the heavier elements of groups 13, 14, 15 and 16.
Recognition status, as metalloids, of some elements in the p-block of the periodic table. Percentages are median appearance frequencies in the lists of metalloids. [n 2] The staircase-shaped line is a typical example of the arbitrary metal–nonmetal dividing line found on some periodic tables.
[12] A study conducted by The Student PIRGs found that a new edition costs 12% more than a new copy of the previous edition (not surprising if the old version is obsolete), and 58% more than a used copy of the previous edition. Textbook publishers maintain these new editions are driven by demand from teachers.
A mnemonic is a memory aid used to improve long-term memory and make the process of consolidation easier. Many chemistry aspects, rules, names of compounds, sequences of elements, their reactivity, etc., can be easily and efficiently memorized with the help of mnemonics.