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picture1_Pdf Printable Periodic Table 194993 | L7(6 7)


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File: Pdf Printable Periodic Table 194993 | L7(6 7)
2 6 elements and the periodic table elements in a group have similar properties periodicity in the properties of the elements elements in a period have different properties mendeleev s ...

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            2.6 Elements and the Periodic Table             • Elements in a group have similar properties
           • Periodicity in the properties of the elements  • Elements in a period have different properties
             –Mendeleev’s table, 1871 – arrangement by      • Metals
              atomic mass                                     –good electrical and heat conductivity, malleable, 
             –Modern version of the table – arrangement by     ductile
              atomic number                                 • Nonmetals
           • Groups – vertical columns in the table           –poor electrical and heat conductivity, neither 
             –Agroups (1, 2, 13-18) – representative elements  malleable nor ductile, often gases or liquids
             –Bgroups (3-12) – transition elements          • Metalloids
             –Inner transition elements – lanthanides & 
              actinides                                       –semiconductors, intermediate properties 
           • Periods – horizontal rows in the table
                                                           • Properties change gradually down in a group
                                                             –Group 1A (1) - alkali metals (Li, Na, K, Rb,...)
                                                                • soft, easy melting metals; react violently with water
                                                                • reactivity increases down in the group
                                                             –Group 2A (2) - alkaline earth metals (Be, Mg, ...)
                                                                • similar but less reactive than Group 1
                                                                • reactivity increases down in the group
                                                             –Group 7A (17) - halogens (F, Cl, Br, I,...)
                                                                • very reactive - reactivity increases up in the group
                                                                • gradual change in physical properties - F, Cl (yellow 
                                                                 gases), Br (red-brown liquid), I (purple-black solid)
                                                             –Group 8A (18) - noble gases (He, Ne, Ar,...)
                                                                • very low reactivity - inert gases
                                                                • colorless, odorless gases
                                                                                                            1
              2.7 Compounds                                           • Ionic compounds – consist of positive and 
             • Combination of two or more elements in                  negative ions held together by electrostatic 
               some definite proportion                                attraction  (NaCl, CaO, ...)
             • Chemical bonds – the forces that hold the                –Positive ions (cations) – often produced when 
                                                                                               +   2+
               atoms of elements together in compounds                   metals lose electrons (Na , Ca , ...) 
               –Ionic bonding – results from transfer of                –Negative ions (anions) – often produced when 
                                                                                                  -  2-
                 electrons from one atom to another                      nonmetals gain electrons (Cl , O , ...) 
               –Covalent bonding – results from sharing of            • Binary ionic compounds – composed of just 
                 electrons between atoms                               2 elements (typically a metal and a nonmetal)
             • Ions – el. charged atoms or groups of atoms            • Monatomic ions – formed through gain or 
             • Molecules – el. neutral groups of atoms                         -
               covalently bonded together                              loss of e by single atoms
             • Formation of binary ionic compounds                    • Charges of monoatomic
             Example:NaCl                                             ions can be predicted 
               –The electrons lost by Na are gained by Cl             from the periodic table
                                                                                              -                  -
                                                                        –Typically metals loose e and nonmetals gain e
                                                                         until they reach the same number of e- as in the 
                                                                         nearest noble gas (high stability)
                                                                        –Groups 1A–3Aform cations with charges equal 
                                                                         to the group#  (only the lighter members of 3A)
                                                                        –Groups 5A–7A-anions with charges equal to the 
                                                                         group# - 8 (only the lighter members of 5&6A)
                                                                                                                             2
             • The strength of ionic bonds depends on the               Problems:
               charges and sizes of the ions                              1. What are the charges of the monatomic 
               –Potential energy of interaction between two ions          ions formed by Al and Br?  
                 with charges q and q separated by a distance r         Al →Group 3A →3+ →Al3+
                              1     2                      12
                                                                                                           -
                                   q ×q                                                          (loss of 3e →Ne)
                            E = 1        2
                               p     r                                  Br →Group 7A →7 –8 = -1 →Br-
                                      12                                                                    -
               ⇒Ions with higher charges and smaller sizes                                       (gain of 1e → Kr)
               attract each other stronger
            • Ionic compounds are neutral → the # of                      2. What is the ratio of Al3+ to Br- ions in the 
              positive charges must equal the # of negative               binary ionic compound of these elements? 
              charges (charge balance)                                  Al3+ :  Br-  → 1 : 3     ← 1(+3) + 3(-1) = 0
             • Covalent compounds – typically consist of                  2.9 Mixtures
               molecules in which atoms are bonded                      • Contain more than one pure substances
               together through sharing of electrons →                  • Heterogeneous mixtures - composition 
               molecular compounds (H O, NH , …)
                                         2       3                        changes from one part to another (soil, blood, 
               –Formed usually between nonmetals                          milk, dust, fog, ...)
               –Some elements occur in nature in a molecular            • Homogeneous mixtures - composition is 
                 form (H , O , N , F , Cl , Br , I , P , S , …)           uniform throughout (sea water, air, gasoline, 
                        2  2   2  2   2   2 2   4  8
             • Polyatomic ions – consist of two or more                   vinegar, brass, ...)
               covalently bonded atoms with a net overall               • Solutions - homogeneous mixtures 
                           +     2-                                       –solvent - present in the larger amount 
               charge (NH , SO , …) →participate in 
                          4      4                                        –solute - the dissolved substance 
               ionic bonding
                                                                        • Aqueous solutions - the solvent is water
                                                                                                                                  3
            • Differences between mixtures and                        − Distillation -
              compounds                                                differences in 
                                                                       the volatility 
                                                                       (boiling point)
            • Separation of mixtures (relies on differences 
              in the physical properties of the components)
               –Extraction - differences in the solubility
               –Filtration - differences in particle size 
            – Chromatography-differences in the ability to 
              adsorb on surfaces or absorb into liquids
               –Stationary and mobile phases
               –GC 
               –LC
                                                                                                                             4
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...Elements and the periodic table in a group have similar properties periodicity of period different mendeleev s arrangement by metals atomic mass good electrical heat conductivity malleable modern version ductile number nonmetals groups vertical columns poor neither agroups representative nor often gases or liquids bgroups transition metalloids inner lanthanides actinides semiconductors intermediate periods horizontal rows change gradually down alkali li na k rb soft easy melting react violently with water reactivity increases alkaline earth be mg but less reactive than halogens f cl br i very up gradual physical yellow red brown liquid purple black solid noble he ne ar low inert colorless odorless compounds ionic consist positive combination two more negative ions held together electrostatic some definite proportion attraction nacl cao chemical bonds forces that hold cations produced when atoms lose electrons ca bonding results from transfer anions one atom to another gain o covalent s...

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