Atoms, Molecules, and Ions. Chapter 2 AP Chemistry

Transcription

1 Atoms, Molecules, and Ions Chapter 2 AP Chemistry

2 Building blocks of chemistry. Atom Molecule Ion

3 Dalton s Atomic Theory 1. An element is composed of tiny particles called atoms. 2. In an ordinary chemical reaction, atoms move from one substance to another, but no atom of any element disappears or is changed into an atom of another element. 3. Compounds are formed when atoms of two or more elements combine.

4 Laws Law of Conservation of Mass Law of Constant Composition Law of Multiple Proportions Cr 2 O 3 CrO 3

5 Components of the Atom Electrons J.J. Thomson in 1897 Particles deflected in Cathode Ray tube Negative one charge Very small mass 1/2000 that of the lightest atom

6 Protons and Neutrons Ernest Rutherford 1911 Gold Foil Experiment using alpha particles nucleus Proton - Moseley Mass equal to H Positive one charge Neutron - Chadwick Mass equal to H No charge

7 Atomic Number, Z Z = Equals the number of protons Mass Numbers and Isotopes Mass number (A) = # protons (Z) + # neutrons Isotopes have same # protons BUT different # of neutrons

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9 Nuclear Stability; Radioactivity There are eight known isotopes of carbon: Of these, two C-12 and C-13 are stable in the sense that they do not decompose over time. The others decompose as time passes into other nuclei. Whether or not a given nucleus will be stable depends on its neutron-to-proton ratio.

10 Band of Stability For light elements, Z<20, this ratio is close to 1 For heavier elements the stable neutron to proton ratio is close to 1.5

11 Unstable iotopes Decompose (decay) by a process referred to as radioactivity. This is also called transmutation of elements. There are three main types of radioactivity. Beta (β) 0 β or 0 e -1-1 Alpha (α) 4 He or 4 α Gamma ( )

12 Silver Sulfur Periodic Table Metals Nonmetals Metalloids Periods Families Main group and transition elements

13 Biologically important elements and highly toxic elements We need the yellow. The red are toxic. The green we need in trace amounts.

14 Molecules Theses molecules are shown in ball and stick form. These are also represented in structural formulas like this: H O H N H H H H H C H H

15 Condensed structural formula Ball and Stick Structural Condensed

16 Diatomics, BRONHIFCL, Twins Elements can exist as molecules. These elements can exist as shown. Notice that P and S have been added to the Twins or BRINCLHOF

17 Some elements have a twin or are diatomic.. The Blue elements like to hang around in pairs. The pink elements P and S hang around in groups the most common is listed. H 2 N 2 S 8 P 4 O 2 F 2 Cl 2 Br 2 I 2

18 Ions When as atom gains or loses an atom is called an ion. Cation if positively charged or giving electrons away. Anion if negatively charged or accepting electrons.

19 Polyatomic ions These are groups of atoms that hang around together and have a charge. Hydroxide ion Ammonium ion

20 Here is a trick to name and know about 48 polyatomic ions. Now to name them Like the chart above (base element name) ate BO 3 CO 3 NO 3 1 more oxygen than above Per -(base element name) ate 1 less oxygen than above (base element name ite 2 less oxygen than above Hypo (base element name) - ite PO 4 O SO 4 F ClO 3 AsO 4 SeO 4 BrO 3 SbO 4 TeO 4 IO 3 Noble Gases

21 Some other polyatomics that you should know are on page 62 of your book. Update your flashcards (or make new)

22 General Charges +1 Many Different Charges -2-1 N O B L E G A S E S Many Different Charges

23 Writing Ionic Formulas A. Ionic compounds are usually a metal/nonmetal combination or contain a polyatomic ion B. Since compounds are neutral, all charges must add to zero (same number of + as -) C. Cation (+) is written first followed by the anion (-) D. Ionic formulas are always empirical (simplest whole number ratio) E. Examples 2L.4-5

24 Naming Compounds JUST NAME You must use Roman Numeral (I, II, II, IV, ) that tells the charge of the metal, to name a transition metal with a non-metal. (Except zinc and silver) J U S T N A M E Roman Numeral Here too! Negative ion change ending to -ide Non-metal bonded with non-metals need mono-, di-, tri-, tetra-, Prefixes on both N O B L E G A S E S You must use Roman Numeral (I, II, II, IV, ) that tells the charge of the metal, to name an inner transition metal with a non-metal.

25 Column #1, #2 or # 13 with a nonmetal (not including H) Just name the first non-metal Name the second, changing the ending of the second element to ide. EXAMPLE: Li 2 O Lithium oxide

26 Naming a compound with a metal and a non-metal Find the charge on the metal element by using the known charge of the non-metal element. Name the first element (the metal). Write the charge of the metal in Roman Numerals. Then write the name of the non-metal changing the last to ide. Example: CuCl 2 Copper (II) Chloride

27 Use the prefixes: Naming a compound with two nonmetals (1) mono-, (2) di-, (3) tri-, (4) tetra-, (5) penta, (6) hexa-, (7) hepta-, (8) octa-, (9) nona-, (10) deca If the first element listed has a quantity of just one then you don t use mono- as a prefix. Put the appropriate prefix in front of the name of each element change the ending to ide. Example: N 2 O 5 Dinitrogen pentaoxide