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Glencoe Chapter 6 Bryce Wolzen
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Dmitri Mendeleev: ◦ Developed the first “modern” periodic table (1869) ◦ Arranged elements according to increasing atomic mass ◦ Predicted places for as yet undiscovered elements ◦ There were exceptions to this arrangement
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Henry Moseley: ◦ Arranged the elements in order of increasing atomic number. ◦ This resulted in clear periodic pattern of properties. Periodic Law: There is a periodic repetition of chemical and physical properties (called periodicity) when elements are arranged by increasing atomic number.
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Arranged in order of increasing atomic number Columns are called families or groups ◦ Elements in a family have similar chemical properties ◦ Also have same number of valence electrons ◦ Coincidence? (No!!) Rows are called periods or series o All elements of a period have the same number of energy levels.
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s-block p-block d-block f-block
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1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 4p 5p 6p 7p 3p 2p 1s 4f 5f
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1. Representative elements: Are in groups 1, 2, and 13-18. Identified by the numbers of electrons in their "s" and/or "p" sublevels. Periodic properties are best illustrated by these elements.
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2. Transition Elements: Are in groups 3-12. Identified by the numbers of electrons in their “d" sublevels.
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3. Inner Transition Elements: Identified by the numbers of electrons in their “f" sublevels.
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Outer-shell (valence) electrons will always be filling "s" and/or "p" sublevels Therefore, there can be a maximum of 8 valence electrons Atoms with filled outer-shells are very stable, the least reactive, or inert. ◦ This is called the octet rule Elements tend to gain or lose electrons to attain an octet Atoms with 1 or 7 valence electrons are the most reactive
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Metals Metalloids Nonmetals
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1. Metals: ◦ Shiny ◦ Solids at room temperature ◦ Good conductors of heat and electricity ◦ Malleable ◦ Ductile Alkali metals: (Group 1) ◦ Most reactive metal family ◦ Electron configuration ends ◦ in s 1 (one valence electron)
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1. Metals (continued): Alkaline earth metals: (Group 2) ◦ Second most reactive metal family ◦ Electron configuration ends in s 2 ◦ two valence electrons 2. Metalloids: ◦ Physical and chemical properties of both metals and nonmetals
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3. Nonmetals: ◦ solids or gases at room temperature ◦ Poor conductors of heat and electricity ◦ Dull and brittle Halogens: ◦ Group 17 ◦ Most reactive nonmetal family ◦ Electron configuration ends in s 2 p 5 (7 valence electrons) Noble Gases: ◦ Group 18 ◦ Least reactive of all chemical ◦ families ◦ Electron configuration ends in s 2 p 6 (8 valence electrons-an octet)
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Atomic radius: measure of the size of an atom typical distance from the nucleus to the boundary of the surrounding electrons. Increases down a group Adding a new energy level Decreases across a series Adding electrons to an existing energy level, which increases the nuclear attraction
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Atomic Radius
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Ionic Radius: Measure of the size of an ion Ion: ◦ A charged particle ◦ Neutral atoms gain or lose electrons to acquire a charge Cation: a positively charged ion ◦ Formed by metals ◦ Have lost electron(s) ◦ Smaller than the corresponding atom because the loss of valence electrons results in the loss of an entire energy level
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Ionic Radius (continued): Anion: a negatively charged ion ◦ Formed by nonmetals ◦ Have gained electron(s) ◦ Larger than the corresponding atom (the number of protons has not changed; therefore, the attraction between the nucleus and the increased number of electrons is weaker).
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Ionization Energy: The energy required to remove an electron from an atom Decreases down a group ◦ Outer electrons are further from the nucleus and easier to remove Increases across a series ◦ As atomic radius decreases across a series, each successive electron is closer to the nucleus and harder to remove (the nuclear attraction is greater – so IE increases.
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Ionization Energy: Metals have lower ionization energies than nonmetals ◦ Easier for them to reach an octet by losing 1-3 electrons rather than gaining 5-7 electrons Nonmetals have higher ionization energies than metals ◦ Easier for them to reach an octet by gaining 1-3 electrons rather than losing 5-7 electrons
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Electron affinity is the change in energy of a neutral atom when an electron is added to the atom to form an anion. In other words, it’s the neutral atom's likelihood of gaining an electron. The greater the energy drop, the greater the stability of the ion to it’s neutral atom. Increases across a period and decreases down a family.
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Electronegativity: Measure of the ability of an atom in a compound to attract electrons Decreases down a group ◦ As radius increases, electrons are further from the bonding atom’s nucleus; therefore, harder to exert attraction for them Increases across a series ◦ As radius decreases, electrons are closer to the bonding atom’s nucleus ; therefore, easier to exert attraction for them
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Electronegativity: Metals have low electronegativity values-they form cations ◦ Easier for them to reach an octet by losing electrons rather than gaining them Nonmetals have high electronegativity values- they form anions Easier for them to reach an octet by gaining electrons rather than losing them
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Electronegativity
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