Octet Rule Main Group elements will gain, lose, or share electrons to get eight valence electrons. Ions Positively or negatively charged atoms Positively charged = cation Negatively charged = anion Formed by gaining or losing electrons Why do atoms gain or lose electrons? To achieve a stable electron configuration Periodic Table IA IIA IIIA IVA VA VIA VIIA VIIIA Trends in Valence Electrons Periodic table shows you how many valence electrons the Main Group Elements have Group 1A has 1 valence electron Group 2A has 2 valence electrons Group 3A has 3 valence electrons Etc. Helium 2 Valence Electrons Carbon 4 Valence Electrons Sodium 1 Valence Electron 2p 2n 6p 6n 11p 12nĮxample Draw electron dot diagrams and determine the number of valence electrons in the following elements: Lithium Beryllium Sodium Magnesium Valence Electrons The electrons in the outermost electron shell. More Examples Carbon 6 protons, 6 neutrons, 6 electrons 1 st Shell: 2 electrons 2 nd Shell: 4 electrons Sodium 11 protons, 12 neutrons, 11 electrons 1 st Shell: 2 electrons 2 nd Shell: 8 electrons 3 rd Shell: 1 electron 11p 12n 6p 6n Example: Helium Nucleus: 2 protons, 2 neutrons 2 electrons in 1 st shell 2p 2n The Modern Periodic Table Atomic Number increases as you go from left to right Organized according to atomic number and electron arrangement (configuration) Įlectron Arrangement Electrons are arranged in energy levels or shells around the nucleus of the atom There are 7 energy levels Each shell holds a set number of electrons 1 st Shell holds up to 2 electrons 2 nd Shell holds up to 8 electrons 3 rd Shell holds up to 18 electrons (8 for main group elements ) 4 th Shell holds up to 32 electrons (8 for main group elements ) Įlectron Dot Diagrams Shells are represented by circles and electrons are represented by dots.
Mendeleev’s Periodic Table Zumdahl, Steven S. Organized according to combining capacity and atomic mass Zumdahl, Steven S. The Early Periodic Table First developed by Dmitri Mendeleev Attempted to place elements with similar properties near each other.
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