The Periodic Table Atoms and the Periodic Table

Dmitri Mendeleev (1869, Russian) –Organized elements by increasing atomic mass. One proton and electron are added to each element as you go across the table. Predicted the existence of undiscovered elements. Dmitri Mendeleev

Henry Mosely (1913, British) –Organized elements by increasing atomic number. –Fixed problems in Mendeleev’s arrangement. Henry Mosely

Metallic Character Metals Nonmetals Metalloids

Metals- good conductors of heat and electricity, Malleable (most metals can be hammered into thin sheets) Nonmetals- gases that are poor conductors of heat and electricity at room temperature, Brittle (breaks easily) Metalloids- Conduct heat and electricity better than nonmetals but not as well as metals, Can be shiny or dull, Solids Metallic Character

Overall Configuration Table Sections Lanthanides - part of period 6 Actinides - part of period 7

Table Sections Representative Elements Transition Metals Inner Transition Metals

Columns & Rows Group (Family) Period

Periodic Law –Properties of elements repeat periodically when the elements are arranged by increasing atomic number. –Moving from left to right in a row of the periodic table, metallic properties decrease. Terms

Valence Electrons –e - in the outermost energy level First Ionization Energy –energy required to remove an e - from a neutral atom Terms

Group # = # of valence e - (except He) –Families have similar reactivity. Period # = # of energy levels Periodic Trends 1A 2A 3A 4A 5A 6A 7A 8A

Region where there is 90% probability of finding an electron. Can’t pinpoint the location of an electron Density of dots represents degree of probability. Orbital

Orbitals have different shapes Orbital

Electrons can only exist at certain energy levels. Low energy levels are close to the nucleus. Each energy level (n) can hold 2n 2 electrons. Energy Levels

Simplified energy levels using Bohr’s idea of circular orbits. Lithium Atomic #:3 Mass: 7 # of p:3 # of e:3 # of n:4 Bohr Model Diagrams p p n n n n p e- Can replace with: 3p 4n Maximum e - Level 12e - Level 28e - Level 38e - Level 418e -

Lewis Structures are visual representations of the bonds between atoms and illustrate the lone pairs of electrons in molecules. They can also be called Lewis dot diagrams and are used as a simple way to show the configuration of atoms within a molecule. Lewis Dot Structures