Modern Periodic Table History and Properties Study Sheet, Schemes and Mind Maps of Chemistry

Download Modern Periodic Table History and Properties Study Sheet and more Schemes and Mind Maps Chemistry in PDF only on Docsity! History of the Periodic Table 1- Berzelius~ 1828 ✓ developed a table of atomic weights & He classified elements into metals and non metals 2- John Newlands ~1864 ✓ The known elements (>60) were arranged in order of atomic weights ✓ Observed similarities between the first and ninth elements, the second and tenth elements etc ✓ He proposed the 'Law of Octaves' 3- Dmitri Mendeleev ~ 1869 ✓ Produced a table based on atomic weights but arranged 'periodically' with elements with similar properties under each other ✓ Gaps were left for elements that were unknown at that time and their properties predicted (the elements were gallium, scandium and germanium) ✓ The order of elements was re-arranged if their properties dictated it 4- Henry Moseley ~1913 ✓ Determined the atomic number of each of the elements ✓ ✓  He modified the 'Periodic Law' to read that the properties of the elements vary periodically with their atomic numbers Traits of the modern periodic table 1- Atomic Radius It is half the distance between the centers of two similar atoms in a diatomic molecule. Atomic radius = Bond length ÷ 2 Problem If bond length in chlorine molecule is 1.98 Å, find atomic radius of a chlorine atom. Solution : Atomic radius of Cl atom = Bond length ÷ 2 = 1.98 ÷ 2 = 0.99 Å ✓ In periods: it decreases across a period Due to the increase in the number of protons and the attraction force. Due to the increase of the nuclear charge ✓ In groups: it increases down a group due to 1. The increase in number of energy levels. 2. The increase in number of electrons and the repulsion force. 3. Inner filled orbitals have a screening effect.