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Chapter 2 Atoms, Molecules, and Ions

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Page 1: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Chapter 2

Atoms, Molecules, and Ions

Page 2: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four
Page 3: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Matter

• What accounts for matters secrets?– Atomists – Democritus– All things are made of Fire – Herclitus– Four Elements – Aristotle

Page 4: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Conservation of Mass and Law of Definite Proportions

• Robert Boyle (1627–1691): Provided evidence for the atomic nature of matter.– Element - A substance that

cannot be chemically broken down further

• Joseph Priestley (1733–1804):

Page 5: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Conservation of Mass and Law of Definite Proportions

• Antoine Lavoisier (1743-1794):

Page 6: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Conservation of Mass

• Law of Mass Conservation: Mass is neither

created nor destroyed in chemical reactions.

Hg(NO3)2 + 2 KI → HgI2 + 2KNO3

3.25g + 3.32g → 4.55g + 2.02g

6.57g = 6.57g

Page 7: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Law of Definite Proportions

• Law of Definite Proportions: In a unique

compound the elements will always be found in

the exact same ratio.

Page 8: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Dalton’s Atomic Theory and the Law of Multiple Proportions

• John Dalton (1766–1844): Proposed explanations for

the laws of mass conservation and definite proportions.– Postulate 1: Elements are made of atoms– Postulate 2: Atoms of the same element have the same

properties (including mass). Atoms of different atoms have

different properties– Postulate 3: Compound are comprise of elements joined

together in small whole ratios– Postulate 4: Chemical reactions only rearrange the way the

atoms are combined

Page 9: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Dalton’s Atomic Theory and the Law of Multiple Proportions

• Law of Multiple Proportions: – When two elements form two different

compounds, the mass ratios are related by small whole numbers.

Page 10: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

The Structure of Atoms: Electrons

• Elements are composed of atoms

• Compounds are composed of atoms of elements in a given ratio

• What does an atom look like?

Page 11: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

The Structure of Atoms• Structure of the Atom:

Page 12: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

The Structure of Atoms

• Comparison of Subatomic particles

Particle Grams amu Coulombs e

Electron 9.109382 x 10-28 0.0005485799 -1.602176 x 10-19 -1

Proton 1.672622 x 10-24 1.007276 1.602176 x 10-19 1

Neutron 1.674927 x 10-24 1.008665 0 0

Page 13: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Atomic Number

• # protons in an atom determines the element – atomic number (Z) - Atomic number is found

on the periodic table

• # electrons = # protons in a neutral atom

Page 14: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Mass Number

• mass of the atom ≈ # neutrons + # protons – Mass number = # protons + # neutrons

– An element may have more than one mass #• Hydrogen, Deuterium, Tritium

• Isotopes: Atoms with identical atomic numbers, but different mass numbers.

• Due to different # of neutrons NOT protons

Page 15: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four
Page 16: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Atomic Mass

• Atomic Mass: A weighted average of the isotopic masses of an element’s naturally occurring isotopes.– Unit – atomic mass unit (amu)

Page 17: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Example

• Chlorine has two naturally occurring isotopes:

with an abundance of 75.77% and an isotopic

mass of 34.969 amu, and with an abundance of

24.23% and an isotopic mass of 36.966 amu.

What is the atomic mass of chlorine?

Page 18: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Compounds and Mixtures

Page 19: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Chemical Bonds

• 2-types of bonding are found in compounds– Ionic bond – Covalent bond

Page 20: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Ionic Bond

Page 21: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Molecules, Ions and Chemical Bonds

• Ionic Bonding (Ionic Solids): Occur between metal and non-metal

Page 22: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Ionic Bonds

Page 23: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Problem

• Which of the following ions occurs commonly? 

– A.  N3+

– B.  S6+

– C.  O2-

– D.  Ca+

– E.  Cl+

Page 24: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Ionic Bonds

Page 25: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Ionic Bonds

• Formula for Ionic Compounds – Ions combine to form neutral compounds

Examples:

Na+ and Cl– combine to form NaCl.

Ca2+ and Cl– combine to form CaCl2.

Al3+ and Cl– combine to form AlCl3.

Fe2+ and Cl- combine to form FeCl2.

Page 26: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Molecules, Ions, and Chemical Bonds

Page 27: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Naming Chemical Compounds

• Naming Ionic Compounds - name the cation, then name the anion.– The positive ion (the metal or ammonium)

• Single charge or ammonium – write its name • More than one possible charge

– Write the elements name – Indicate the magnitude of charge as a roman numeral in

parenthesis

– The negative ion (non-metal or polyatomic ion)• Non-metal element - write root of element name with suffix –ide• Polyatomic – write the ions name

Page 28: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Problem

• Which one of the following combinations of names and formulas of ions is incorrect? 

– A.  O2- oxide

– B.  Al3+ aluminum

– C.  NO3- nitrate

– D.  PO43- phosphate

– E.  CrO42- chromate

Page 29: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Problem

• Which one of the following combinations of names and formulas of ions is incorrect? 

– A.  Ba2+ barium– B.  S2- sulfate– C.  CN- cyanide

– D.  ClO4- perchlorate

– E.  HCO3- bicarbonate

Page 30: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Problem

• Convert the names into formulas and the formulas into names– Sodium oxide– BaO

– CoCl2– (NH4)2S

– Zinc Acetate– Chromium (VI) oxide

Page 31: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Covalent Bond

Page 32: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Molecules, Ions and Chemical Bonds

• Covalent Bonding (Molecules): Between 2 non-metals or a non-metal and a metalloid.

Page 33: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Covalent Bonds

Page 34: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Naming Chemical Compounds

• Naming Binary Molecular Compounds:

– Identify which element is more cationlike.

Page 35: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Naming Chemical Compounds

• If cation-like element is H and anion-like element is O, S, Se, or a halogen– Name hydrogen– Name the anion-like element using root and –

ide ending

Page 36: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Naming Chemical Compounds

• All other non-metal / metalloid combinations– Name the cation-like element– Name the anion-like element with root and –ide– Using prefixes indicate how many of each atom

is present

Page 37: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Covalent Compounds

• Formula– Translate name of each element– Make the prefix of the element it’s subscript

Page 38: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Problem

• Convert formulas into names and names into formulas– PCl3– Diiodine pentoxide

Page 39: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Naming Compounds

• Acids – are a special type of covalent compound– Acids are species that dissociate to form H+

cations and an anion when added to water.• Hence you will need to be told that they are

aqueous compounds (aq)

– Acids are typically indicated by writing the H first in the formula

• Elemental symbols are typically written in alphabetical order

Page 40: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Naming Compounds

• Acids cont.– For current purposes, acids are going to be

described as aqueous compounds of H combined with a group 17 element or a polyatomic ion.

– H with group 17 elements or cyanide• Named as hydro + 17 element root + ic

– H with all other polyatomic ions• Root of polyatomic ions ending in -ate + ic• Root of polyatomic ions ending in –ite + ous

Page 41: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Problem

• What is the name of the acid formed when HBr gas is dissolved in water? 

– A.  bromic acid– B.  bromous acid– C.  hydrobromic acid– D.  hydrobromous acid– E.  hydrobromidic acid

Page 42: Chapter 2 Atoms, Molecules, and Ions. Matter What accounts for matters secrets? –Atomists – Democritus –All things are made of Fire – Herclitus –Four

Optional Homework

• Text – 2.26, 2.28, 2.29, 2.38, 2.46, 2.48, 2.50, 2.52, 2.54, 2.56, 2.58, 2.68, 2.78, 2.82, 2.84, 2.86, 2.88, 2.90, 2.96, 2.100, 2.104, 2.112

• Chapter 2 Homework – from website


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