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Ch. 14 Notes---Chemical Periodicity Valence Electrons and Electron Dot Notations What are “valence electrons”? • outer most energy level These are the electrons in the _________-_______ (or shell). p electrons only. s electrons and “___” • They will be “___” Counting Valence Electrons • Group A # = number of valence electrons 2 e-’s) (only exception Helium = __ 2 e-’s Nitrogen = __ 5 e-’s Argon = __ 8 e-’s Examples: Ca = __ • 2 d-block and f-block = ___valence e-’s Drawing Valence Electrons • “Electron-dot notation”: Electrons will be represented as dots located around the symbol of the element in the pattern shown below. 8 3 2 7 X 5 1 4 6 Examples: Nitrogen = N Hydrogen = (Important Exception: Helium) H He Valence Electrons On The Periodic Table 1 8 2 3 4 5 6 7 Sucktastic! Assume 2 The Development of the Periodic Table • Dmitri Mendeleev _________________________: constructed the 1st periodic table Features of Mendeleev’s Periodic Table (See p.390) • • blank _________ spaces for “missing elements”. Later when He left ______ these elements were discovered, he filled in the gaps. He arranged the elements in columns and rows according to their properties __________________. Elements with similar properties were in the same horizontal row. • predict He was able to accurately ___________ the properties of the missing rows elements based on the properties of the elements in similar _______. • atomic ___________. mass He ordered the elements by increasing __________ Features of the Modern Periodic Table (See Fig. 14.2) • • • • Moseley In 1913, Henry ______________ determined the atomic number, (# p+ of the elements. of ___), – He then arranged the elements in the periodic table by increasing number atomic ____________. – This switched the position of some elements. This is how the modern periodic table is arranged today. Periods or Series Horizontal Rows = ____________ Groups Vertical Columns = ____________ or Families groups families have similar properties. Elements in the same _________/_________ Parts of the Periodic Table • left of the dark zig-zag line running Metals: located to the _______ f through the “p-block”. This includes the elements in the ___-block. Properties of Metals – shiny surface malleable (you can pound it into a flat sheet) – ______________ ductile – ______________ (you can draw it into a thin wire) conductors – good _______________ (heat/electricity travels through it easily) Parts of the Periodic Table • Nonmetals: located to the ___________ right of the dark zig-zag line. Properties of Nonmetals dull surface – _______ brittle – ______________ insulators – good _______________ (or poor conductors) • Metalliods: located on the border of the dark zig-zag line. Examples: Silicon & Germanium – Properties of Metalliods semiconductors (Used in computer chips) ___________________ Parts of the Periodic Table • • d-block metals: “_________________ transition metals” rare-earth metals” f-block metals: “Inner-transition metals” or “____________ Special Group/Family Names • Alkali metals” Group 1A: “_________ water to form a base – React with _________ • Alkaline-earth metals” Group 2A: “________________ – Compounds are used in batteries • Halogens Group 7A: “_________________” – Used in some light fixtures • Noble gases” Group 8A (or 0 or 18): “_______ inert – Don’t form compounds (_________) Parts of the Periodic Table Trends in the Periodic Table Atomic Size (Atomic Radius) (See Fig. 14.10) • increases Moving Down a Group= the size of the atoms ________________ – • more of electrons to higher and Why? You are adding ________ higher energy levels (farther and farther out.) decreases Moving Across a Period= the size generally ______________ – Why? You are adding more e- and p+ to the same energy attraction level. This causes more ______________ of opposite pulls the electron cloud inward. charges and it __________ Trends in the Periodic Table Atomic Size vs. Ion Size (See Fig. 14.8) • removing e-’s. Cation = (___) + charged atom created by ___________ smaller – Cations are ______________ than the original atom. Metals generally form cations. – _____________ • adding Anion = (___) e-’s. − charged atom created by _____________ larger – Anions are ____________ than the original atom. Nonmetals – _______________ generally form anions. Trends in the Periodic Table Atomic Size vs. Ion Size Trends in the Periodic Table Ionization Energy (See Table 14.1 & Fig. 14.12) • • remove Ionization energy is the energy required to _______________ the outer most electron in an atom. decreases Moving Down a Group= _______________ (less energy is needed) – Why? You are trying to remove an electron that is farther and farther out (for larger and larger atoms). These e-’s attracted are not as ________________to the nucleus. less attracted it is to its e-’s. – In general, the larger the atom, the ____ Trends in the Periodic Table Ionization Energy • increases Moving Across a Period= generally ________________ – Why? Moving across a period takes us from metals to nonmetals. More ionization energy is needed for nonmetals metals ______________ compared to __________. cations it won’t take as – Also, since metals generally form _________, much energy to remove it’s outer most electron. – Remember that as you move across the period, the atoms get smaller and therefore ______ more attracted to the electrons. _________ Trends in the Periodic Table “Successive Ionization Energies” (See Table 14.1) • “Successive Ionization Energies” means the energy required to 2nd or a _____ 3rd electron from an atom. remove a _____ more and ______ more – Removing more and more e-’s requires ______ energy. – Why? tightly _________ bound The remaining e-’s are more _________ to the nucleus. Trends in the Periodic Table Electronegativity (See Table 14.2) • • 0 – 4.0 which Electronegativity is a relative value (from_________) compares how much an atom is attracted to the e-’s in a chemical bond. ____________ decreases Moving Down a Group= generally ______________ (less attraction) – Why? The bonded electron is farther and farther out. These e-’s will not be as attracted to the larger and larger atoms. Trends in the Periodic Table Electronegativity • increases Moving Across a Period= generally _________________ – Why? smaller so they are Again, the atoms are getting ________ more attracted to the bonding electrons. _______ – Also, moving across a period takes us from metals to anions nonmetals. Since nonmetals generally form _________, they gain tend to __________ e-’s anyway, and this makes them highly ________________ attracted to e-’s when forming a chemical bond. Noble __________ gases – ___________ are not listed in Table 14.2 since form _____________ compounds ! they do not ________ Determining the Ion Formed • Atoms try to achieve a ________ noble ______ gas configuration when forming an ion. (This makes them more stable.) – Locate the nearest noble gas and count how many “places” it is away, but remember that you can skip over the d-block!! – This amount will be the same as the # of e-’s either gained or lost by the atom when forming an ion. Practice Problem: How many electrons are gained or lost when forming an ion from the following elements? 2 (gained or lost) b) Iodine: ____ 1 (gained or lost) a) Magnesium: ____ 3 (gained or lost) c) Gallium:____ 3 (gained or lost) d) Boron:____