Dalton's Atomic Theory

 

1.  Elements are composed of atoms.

·        Atom: the smallest particle of an element that retains the properties of that element.

·        Molecule: a group of atoms chemically bonded together; the smallest particle of a compound that retains the properties of that compound. 

·        1 molecule of the compound sucrose (C12H22O11) contains 12 Carbon atoms, 22 Hydrogen atoms, and 11 Oxygen atoms.

·        Note:  Some elements exist as molecules.

Br2, I2, N2, Cl2, H2, O2, F2 are referred to as diatomic molecules.  P4 and S8 are referred to as polyatomic molecules.

 

2.  All atoms of a given element have properties which make them alike.  Atoms of different elements have properties which make them different.

·        Elements differ in the number of subatomic particles they contain.

 

3.  Atoms cannot be created, destroyed or transformed into atoms of another element.

·        Law of Conservation of Matter

 

4.  Compounds are formed when atoms of different elements combine in whole number ratios.

 

5.   The number and kinds of atoms are constant in a given compound.

·        Law of Definite Proportions: a specific compound always contains the same elements in the same proportions.

·        Law of Multiple Proportions: the same elements may combine in more than one proportion, with each different proportion yielding a different compound.

            ex:       H2O = water

                        H2O2 = hydrogen peroxide

 

Subatomic particles     

1)  Proton: 

positively charged particle (+1)

Weight:          1.0073 atomic mass unit (amu)

                                    (1 amu = 1.6605 x 10-24 g)

2)  Electron:

negatively charged particle (-1)

Weight:          0.00054858 amu

3)  Neutron:

neutral particle

Weight:          1.0087 amu

·        Positively charged protons are attracted to negatively charged electrons.  Incredibly strong binding forces hold the protons and neutrons together in the nucleus.

·        Atoms are neutral in charge -- contain equal numbers of protons and electrons.     

·        Protons and neutrons are found in the nucleus.  Electrons occupy a large region of space around the nucleus (electron cloud) and are in motion.

·        Atomic number: number of protons.  Each element has a different atomic number.

 

 

Introduction to the Periodic Table

 

Dimitri Mendeleev (1869)

 

•    Arranged elements in order of increasing atomic weights

           

•    Observed a periodic recurrence of elements with similar properties

           

•    There were exceptions to this ordering by atomic weights.

                                                                                                                                               

 

Henry Moseley (1913) 

 

•    Arranged elements in order of increasing atomic number

                       

Periodic law: properties of elements are periodic functions of their atomic numbers

 

 

Features: 

·        Elements are arranged in order of increasing atomic number.                         

·        New rows started so that elements having similar properties fall into columns.       

·        Periods (horizontal rows)

   Groups (vertical columns)

Metals

Non-metals

·        Al, Cu, Fe, Pb

·        C, N, O, S

·        solids

·        gases or solids

·        metallic luster

·        variety of appearances

·        good conductors of heat and electricity

·        insulators

·        malleable and ductile

·        brittle and non-ductile

·        Metallic character increases to the lower left; non-metallic increases to the upper right

·        Semi-metals (staircase): properties intermediate between metals and non-metals

·        Main group elements: (Groups 1,2, 13-18)

·        Transition metals: d and f sub-levels (3 –12)

·        Groups: alkali metals (1), alkaline earth metals (2), halogens (17), noble gases (18)

 

 

Ion:  charged particle formed by the gain or loss of electrons

            Example:  Na+, Cl-

·        Polyatomic Ions: Charged particles containing two or more atoms.      (See Table 2-3, p. 49.)

·        Attractions between oppositely charged ions result in formation of ionic bonds.

           

Chemical Formula: Symbols for the elements in a compound indicate types and subscripts indicate numbers of atoms in one unit.

·        Ions combine in whole number ratios so that the net compound is neutral in charge.

·        Ex.  NaCl,  CaCl2,  MgSO4, Ca(NO3)2

·        Charges are not shown in the formula for the compound.

·        Ionic compounds are not molecules. They are a repeating network of ions.

 

 

Naming compounds

 

Binary compounds contain two different elements combined in a specific ratio.

·        Binary ionic compounds contain a metal ion and a nonmetal ion.

Ex.  CaCl2, CaS, Na2O

·        Pseudobinary ionic compounds contain two ions, with at least one of them being a polyatomic ion.

Ex. Na2SO4, NH4Cl, (NH4)3PO4

 

Most transition metals and metals of groups 13, 14, and 15 exhibit more than one oxidation state (charge).  Consequently they can form more than one binary or pseudobinary ionic compound when combined with the same anion.

·        Common exceptions include: Ag+, Zn2+, Al3+

·        Common examples include: Cu+, Cu2+, Fe2+, Fe3+, Sn2+, Sn4+, Pb2+, Pb4+

·        Names for these ions require a Roman numeral to indicate the oxidation state. Ex: Tin (II), etc.

·        When naming an ionic compound, name the cation first then the anion.  No prefixes are used to indicate the number of ions present.

·        Name the following:

ZnCl2                                                                               PbI2

NH4NO3                                                                          Sn(SO4)2       

Ba3P2                                                                               AlF3

·        Binary molecular compounds contain two nonmetal atoms.

Ex. N2O5, HF, CO2

·        Names require prefixes which indicate the number of each element.

·        Prefixes used are as follows:

mono-             1 (omitted for first element)

di-                   2

tri-                  3

tetra-              4

penta-            5

hexa-              6

hepta-            7

octa-               8

nona-              9

deca-               10

 

Name the following compounds:

 

1.         NaHCO3

2.         CuSO4

3.         NaOH

4.         CO                 

5.         CaCl2

6.         MgBr2

7.         H2O

8.         Fe2O3

9.         KF

10.       AlN

11.       FeCO3

12.       NO

13.       Fe(NO3)3

14.       N2O

 

Write formulas for the following compounds:

 

1.         Carbon dioxide

2.         Aluminum phosphate

3.         Sodium carbonate

4.         Calcium nitrate

5.         Magnesium hydroxide

6.         Ammonium acetate

7.         Iron (II) hydroxide

8.         Sulfur hexafluoride

9.         Silver chloride

10.       Zinc nitrate

11.       Phosphorous tribromide

12.       Copper (I) bromide

13.       Copper (II) chloride

14.       Diphosphorous pentaoxide

 

 

Naming binary acids

 

Binary acids are compounds of hydrogen and other non-metals (often a halogen), but no oxygen.

·                   Names for these acids use the format hydro                 ic acid, with the blank corresponding to the element involved

Ex.            HCl = hydrochloric acid

                  HBr = hydrobromic acid

                  HF = hydrofluoric acid

                  HI = hydroiodic acid

                  HCN = hydrocyanic acid

 

Naming ternary acids

 

Ternary acids (oxoacids) are compounds of hydrogen, oxygen and a non-metal.

·        The hydro- prefix is not used

·        Names for these acids are related to the names of corresponding polyatomic ions.

·        In the acid name, the suffix –ic is used when working with polyatomic ions with –ate endings; the suffix –ous is used when working with polyatomic ions with the –ite ending.

Ex.

                        HClO3 = chloric acid

                        HClO2 = chlorous acid

 

                        H2SO4 = sulfuric acid

                        H2SO3 = sulfurous acid

 

                        HNO3 =