Sorry my dear friends for not being able to post since last two months but there is an amazing news for all my friends who are appearing for boards this march and also for the JEE Mains aspirants for their next attempt. So friends from today onward I will help you all by posting really important concepts of the chapters of PCM that are there in the NCERT. How is it helpful for Jee Mains aspirants? See, these posts will also cover the topics that most of the JEE aspirants leave like Communication System (which is our today's topic), Bio molecules etc. And as you know that this year 40% of question in JEE Mains are directly from NCERT. I hope you understand what I wanted to say. So please guys just go through these points everyday for the next 30 days and you will be exam ready. Its just for making your present workload easy. If you have read a certain chapter then this will be like revision for you and for the first time learners this is a comprehensive note form of NCERT and that's what is important. Lets see you there ;)
Mendeleev arranged 63 elements known at that time in the periodic table. According to Mendeleev “the properties of the elements are a periodic function of their atomic masses.” The table consists of eight vertical column called ‘groups’ and horizontal rows called ‘periods’ Limitations of mendeleev’s classification : (i) He could not assign a correct position of hydrogen in his periodic table, as the properties of hydrogen resembles both with alkali metals as well as with halogens. (ii) The isotopes of the same element will be given different position if atomic number is taken as basis, which will disturb the symmetry of the periodic table. (iii) The atomic masses do not increases in a regular manner in going from one elements to the next. So it was not possible to predict how many elements could be discovered between two elements.
Comments
Post a Comment