4.1 Development of the Periodic Table: Mendeleev, Moseley & the Periodic Law

Chapter 4: Periodic Trends | Lecture 1 of 10 General Chemistry: The Complete College Lecture Series This chapter covers effective nuclear charge, atomic and ionic radius, ionization energy, electron affinity, metallic character and the electron configurations of ions. This lecture traces how the periodic table was developed and why the elements are arranged the way they are today. We begin with the roughly 60 elements known by the 1840s, early attempts to find patterns such as Newlands' law of octaves, and Dmitri Mendeleev's periodic table, which grouped elements with similar chemical and physical properties, left gaps for undiscovered elements and predicted their properties. We discuss the disadvantages of Mendeleev's table, including ordering by atomic mass, and how Henry Moseley showed that the table should be organized by atomic number, the number of protons. Today the table holds 118 elements, including man-made elements discovered after 1965. The lecture ends with a practice question on identifying elements with similar properties by looking above, below and next to an element in the table. These are comprehensive general chemistry lecture videos, built to help students succeed in the course, with clear step-by-step explanations, closed captions and practice quiz questions. Timestamps: 0:00 Development of the periodic table 2:14 118 elements in the modern periodic table 4:23 Looking above, below and beside an element Part of: General Chemistry, Chapter 4 Keywords: periodic table history, Mendeleev, Moseley, law of octaves, periodic law, atomic number, groups and periods Related search terms: MCAT chemistry, DAT chemistry, OAT chemistry, PCAT chemistry, AP Chemistry, IB Chemistry, CLEP general chemistry, A-level chemistry, NEET chemistry, JAMB chemistry, community college chemistry, college general chemistry #GeneralChemistry #Chapter4 #PeriodicTable #Mendeleev #PeriodicTrends #DrKunapareddy