History of Periodic Table and Periodicity

Mendeleev organized the elements based on their properties and developed the first periodic table He left blanks based on chemical properties and elements were later discovered to fill in the blanks Later it was discovered that the periodic table became “more correct” if the elements were arranged by atomic number

Alkali metals, alkaline earth metals, transition metals, metalloid, halogens, noble gases, lanthanides, actinides Properties of elements: conductors, reactivity

Periodicity Must know 3 periodic trends and why that trend occurs

Atomic Radii one half the distance between bonded atoms Decreases to the right on the periodic table due to the increasing positive charge of the nucleus Increases down the periodic table due to adding new energy levels There are a few exceptions due to electron configurations

Ionization Energy The energy required to remove one electron from a neutral atom Increases to the right due to increasing nuclear charge and decreasing atomic radii Decreases down due to a larger atomic radii Second ionization energy is always higher than first Harder to remove an electron from a positive ion

Electronegativity A measure of the ability of an atom to attract electrons Increases to the right Increases up Due to atomic radii, nuclear charge, and electron configuration F is the most electronegative element Noble gases have 0 electronegativity

Choose the element with the larger atomic radius Mg Cl S Se Ni Fe S Br

Choose the element with the higher electronegativity Br I Al Si Mg Ca P Ar

Choose the element with the Lower ionization energy P S Ar Mg Ca Sr Cu Ag

Ne, P, Fe, Ca, Cs, Al, Zn Arrange the above elements in order of increasing ionization energy Arrange the elements above in order of increasing atomic radius Arrange the elements above in order of decreasing electronegativity