Atoms, Molecules, and Ions

Dalton’s Atomic Theory 1) Elements are made up of atoms 2) Atoms of each element are identical. Atoms of different elements are different. 3) Compounds are formed when atoms combine. Each compound has a specific number and kinds of atom. 4) Chemical reactions are rearrangement of atoms. Atoms are not created or destroyed.

Laws Conservation of Mass Conservation of Mass Law of Definite Proportion- compounds have a constant composition. Law of Definite Proportion- compounds have a constant composition. They react in specific ratios by mass. They react in specific ratios by mass. Law of Multiple Proportions- When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers. Law of Multiple Proportions- When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers.

What?! Water has 8 g of oxygen per g of hydrogen. Water has 8 g of oxygen per g of hydrogen. Hydrogen peroxide has 16 g of oxygen per g of hydrogen. Hydrogen peroxide has 16 g of oxygen per g of hydrogen. 16/8 = 2/1 16/8 = 2/1 Small whole number ratios. Small whole number ratios.

Proof Mercury has two oxides. One is 96.2 % mercury by mass, the other is 92.6 % mercury by mass. Mercury has two oxides. One is 96.2 % mercury by mass, the other is 92.6 % mercury by mass. Show that these compounds follow the law of multiple proportion. Show that these compounds follow the law of multiple proportion. Speculate on the formula of the two oxides. Speculate on the formula of the two oxides.

Gay-Lussac- under the same conditions of temperature and pressure, compounds always react in whole number ratios by volume. Gay-Lussac- under the same conditions of temperature and pressure, compounds always react in whole number ratios by volume. Avagadro- interpreted that to mean at the same temperature and pressure, equal volumes of gas contain the same number of particles. Avagadro- interpreted that to mean at the same temperature and pressure, equal volumes of gas contain the same number of particles. (called Avagadro’s Hypothesis) (called Avagadro’s Hypothesis) A Helpful Observation

Experiments to determine what an atom was J. J. Thomson- used Cathode ray tubes J. J. Thomson- used Cathode ray tubes

Thomson’s Experiment Voltage source +-

Thomson’s Experiment Voltage source +-

n Passing an electric current makes a beam appear to move from the negative to the positive end. Thomson’s Experiment Voltage source +-

Thomson’s Experiment By adding an electric field

Voltage source Thomson’s Experiment n By adding an electric field, he found that the moving pieces were negative + -

Thomsom’s Model Found the electron. Found the electron. Couldn’t find positive (for a while). Couldn’t find positive (for a while). Said the atom was like plum pudding. Said the atom was like plum pudding. A bunch of positive stuff, with the electrons able to be removed. A bunch of positive stuff, with the electrons able to be removed.

Millikan’s Experiment Oil Atomizer Oil droplets Telescope - +

Millikan’s Experiment X-rays X-rays give some electrons a charge.

Millikan’s Experiment Some drops would hover From the mass of the drop and the charge on the plates, he calculated the mass of an electron

Rutherford’s Experiment Used uranium to produce alpha particles. Used uranium to produce alpha particles. Aimed alpha particles at gold foil by drilling hole in lead block. Aimed alpha particles at gold foil by drilling hole in lead block. Since the mass is evenly distributed in gold atoms alpha particles should go straight through. Since the mass is evenly distributed in gold atoms alpha particles should go straight through. Used gold foil because it could be made atoms thin. Used gold foil because it could be made atoms thin.

Lead block Uranium Gold Foil Florescent Screen

What he expected

Because

Because, he thought the mass was evenly distributed in the atom.

What he got

How he explained it + Atom is mostly empty Atom is mostly empty Small dense, positive piece at center. Small dense, positive piece at center. Alpha particles are deflected by it if they get close enough. Alpha particles are deflected by it if they get close enough.

+

Modern View The atom is mostly empty space. The atom is mostly empty space. Two regions Two regions Nucleus- protons and neutrons. Nucleus- protons and neutrons. Electron cloud- region where you might find an electron. Electron cloud- region where you might find an electron.

Sub-atomic Particles Z - atomic number = number of protons determines type of atom. Z - atomic number = number of protons determines type of atom. A - mass number = number of protons + neutrons. A - mass number = number of protons + neutrons. Number of protons = number of electrons if neutral. Number of protons = number of electrons if neutral.

Symbols X A Z Na 23 11

Chemical Bonds The forces that hold atoms together. The forces that hold atoms together. Covalent bonding - sharing electrons. Covalent bonding - sharing electrons. Makes molecules. Makes molecules. Chemical formula- the number and type of atoms in a molecule. Chemical formula- the number and type of atoms in a molecule. C 2 H carbon atoms, 6 hydrogen atoms, C 2 H carbon atoms, 6 hydrogen atoms, Structural formula shows the connections, but not necessarily the shape. Structural formula shows the connections, but not necessarily the shape.

H H HH H HCC There are also other model that attempt to show three dimensional shape. There are also other model that attempt to show three dimensional shape. Ball and stick. Ball and stick.

Ions Atoms or groups of atoms with a charge. Atoms or groups of atoms with a charge. Cations- positive ions - get by losing electrons(s). Cations- positive ions - get by losing electrons(s). Anions- negative ions - get by gaining electron(s). Anions- negative ions - get by gaining electron(s). Monatomic ions – chart pg. 73 Monatomic ions – chart pg. 73 Ions of transition metals – chart pg. 75 Ions of transition metals – chart pg. 75 Monatomic negative ions – chart pg. 81 Monatomic negative ions – chart pg. 81

Polyatomic Ions Groups of atoms that have a charge. Groups of atoms that have a charge. Yes, you have to memorize them. Yes, you have to memorize them. A charged group of covalently bonded atoms that generally act as a group. A charged group of covalently bonded atoms that generally act as a group. Polyatomic ion chart – pg. 76. Polyatomic ion chart – pg. 76.

Periodic Table

Classification Blocks Groups Periods

Metals Conductors Conductors Lose electrons Lose electrons Malleable and ductile Malleable and ductile

Nonmetals Brittle Brittle Gain electrons Gain electrons Covalent bonds Covalent bonds

Non-metals are generally called oxidizers – because they accept electrons readily Metals are referred to as reducers because they give up electrons readily

Semi-metals or Metalloids

Alkali Metals

Alkaline Earth Metals

Halogens

Transition metals

Noble Gases

Inner Transition Metals

Naming compounds Two types Two types Ionic - metal and non metal or polyatomics. Ionic - metal and non metal or polyatomics. Covalent- we will just learn the rules for 2 non-metals. Covalent- we will just learn the rules for 2 non-metals.

Ionic compounds If the cation is monoatomic- Name the metal (cation) just write the name. If the cation is monoatomic- Name the metal (cation) just write the name. If the cation is polyatomic- name it If the cation is polyatomic- name it If the anion is monoatomic- name it but change the ending to -ide If the anion is monoatomic- name it but change the ending to -ide If the anion is poly atomic- just name it If the anion is poly atomic- just name it practice practice

Ionic Compounds Have to know what ions they form Have to know what ions they form off table, polyatomic, or figure it out off table, polyatomic, or figure it out CaS CaS K 2 S K 2 S AlPO 4 AlPO 4 K 2 SO 4 K 2 SO 4 FeS FeS CoI 3 CoI 3

Ionic Compounds Fe 2 (C 2 O 4 ) Fe 2 (C 2 O 4 ) MgO MgO MnO MnO KMnO 4 KMnO 4 NH 4 NO 3 NH 4 NO 3 Hg 2 Cl 2 Hg 2 Cl 2 Cr 2 O 3 Cr 2 O 3

Ionic Compounds KClO 4 KClO 4 NaClO 3 NaClO 3 YBrO 2 YBrO 2 Cr(ClO) 6 Cr(ClO) 6

Naming Covalent Compounds Two words, with prefixes Two words, with prefixes Prefixes tell you how many. Prefixes tell you how many. mono, di, tri, tetra, penta, hexa, septa, nona, deca mono, di, tri, tetra, penta, hexa, septa, nona, deca First element whole name with the appropriate prefix, except mono First element whole name with the appropriate prefix, except mono Second element, -ide ending with appropriate prefix Second element, -ide ending with appropriate prefix Practice Practice

CO 2 CO 2 CO CO CCl 4 CCl 4 N 2 O 4 N 2 O 4 XeF 6 XeF 6 N 4 O 4 N 4 O 4 P 2 O 10 P 2 O 10 Naming Covalent Compounds

Writing Formulas Two sets of rules, ionic and covalent Two sets of rules, ionic and covalent To decide which to use, decide what the first word is. To decide which to use, decide what the first word is. If is a metal or polyatomic use ionic. If is a metal or polyatomic use ionic. If it is a non-metal use covalent. If it is a non-metal use covalent.

Ionic Formulas Charges must add up to zero. Charges must add up to zero. Get charges from table, name of metal ion, or memorized from the list. Get charges from table, name of metal ion, or memorized from the list. Use parenthesis to indicate multiple polyatomics. Use parenthesis to indicate multiple polyatomics.

Ionic Formulas Sodium nitride Sodium nitride sodium- Na is always +1 sodium- Na is always +1 nitride - ide tells you it comes from the table nitride - ide tells you it comes from the table nitride is N -3 nitride is N -3

Ionic Formulas Sodium nitride Sodium nitride sodium- Na is always +1 sodium- Na is always +1 Nitride - ide tells you it comes from the table Nitride - ide tells you it comes from the table nitride is N -3 nitride is N -3 Doesn’t add up to zero. Doesn’t add up to zero. Na +1 N -3

Ionic Formulas Sodium nitride Sodium nitride sodium- Na is always +1 sodium- Na is always +1 nitride - ide tells you it comes from the table nitride - ide tells you it comes from the table nitride is N -3 nitride is N -3 Doesn’t add up to zero Doesn’t add up to zero Need 3 Na Need 3 Na Na +1 N -3 Na 3 N

Ionic Compounds Sodium sulfite Sodium sulfite calcium iodide calcium iodide Lead (II) oxide Lead (II) oxide Lead (IV) oxide Lead (IV) oxide Mercury (I) sulfide Mercury (I) sulfide Barium chromate Barium chromate Aluminum hydrogen sulfate Aluminum hydrogen sulfate Cerium (IV) nitrite Cerium (IV) nitrite

Covalent compounds The name tells you how to write the formula The name tells you how to write the formula duh duh Sulfur dioxide Sulfur dioxide diflourine monoxide diflourine monoxide nitrogen trichloride nitrogen trichloride diphosphorus pentoxide diphosphorus pentoxide

More Names and formulas

Acids Substances that produce H + ions when dissolved in water. Substances that produce H + ions when dissolved in water. All acids begin with H. All acids begin with H. Two types of acids: Two types of acids: Oxyacids Oxyacids Non-oxyacids Non-oxyacids

Naming acids If the formula has oxygen in it If the formula has oxygen in it write the name of the anion, but change write the name of the anion, but change ate to -ic acid ate to -ic acid ite to -ous acid ite to -ous acid Watch out for sulfuric and sulfurous Watch out for sulfuric and sulfurous H 2 CrO 4 H 2 CrO 4 HMnO 4 HMnO 4 HNO 2 HNO 2

Naming acids If the acid doesn’t have oxygen If the acid doesn’t have oxygen add the prefix hydro- add the prefix hydro- change the suffix -ide to -ic acid change the suffix -ide to -ic acid HCl HCl H 2 S H 2 S HCN HCN

Formulas for acids Backwards from names. Backwards from names. If it has hydro- in the name it has no oxygen If it has hydro- in the name it has no oxygen Anion ends in -ide Anion ends in -ide No hydro, anion ends in -ate or -ite No hydro, anion ends in -ate or -ite Write anion and add enough H to balance the charges. Write anion and add enough H to balance the charges.

Formulas for acids hydrofluoric acid hydrofluoric acid dichromic acid dichromic acid carbonic acid carbonic acid hydrophosphoric acid hydrophosphoric acid hypofluorous acid hypofluorous acid perchloric acid perchloric acid phosphorous acid phosphorous acid

Hydrates Some salts trap water crystals when they form crystals. Some salts trap water crystals when they form crystals. These are hydrates. These are hydrates. Both the name and the formula needs to indicate how many water molecules are trapped. Both the name and the formula needs to indicate how many water molecules are trapped. In the name we add the word hydrate with a prefix that tells us how many water molecules. In the name we add the word hydrate with a prefix that tells us how many water molecules.

Hydrates In the formula you put a dot and then write the number of molecules. In the formula you put a dot and then write the number of molecules. Calcium chloride dihydrate = CaCl 2  2  Calcium chloride dihydrate = CaCl 2  2  Chromium (III) nitrate hexahydrate = Cr(NO 3 ) 3  6H 2 O Chromium (III) nitrate hexahydrate = Cr(NO 3 ) 3  6H 2 O