Download Chapter 2: Atoms, Molecules, and Ions

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Honors Unit 2 Notes: Atoms, Molecules, and Ions
Objectives:
1. Students will be familiar with the laws of chemical composition: law of conservation of mass, law of
multiple proportions, and law of constant composition.
2. Students will become familiar with the work of classical atomic theorists such as Lavoisier and Dalton.
3. Students will be able to state the number of protons, electrons and neutrons in neutral atoms, ions,
and isotopes.
4. Students will understand the derivation and meaning of atomic mass and be able to calculate
weighted average masses from isotopic data.
5. Students will become familiar with the work of Mendeleev and know the location of groups, periods,
metal, nonmetals, and metalloids on the periodic table.
6. Students will be able to distinguish between molecular and ionic formulas and be able to write
formulas for and name simple binary molecular compounds.
7. Students will be able to write formulas for, and name, binary ionic and polyatomic ionic compounds.
Atoms, Atomic Theory, and Components of the Atom
•
Atoms – Composed of electrons, protons and neutrons
•
Molecules – _____________________________________________
•
Ions – _____________________________________________
A. Antoine Lavoisier: Law of Conservation of Mass or Matter (1790)
_________________________remains _______________during a
chemical reaction; or
Total mass of _________________ = total mass of _________________.
B. Joseph Proust: Law of Constant Composition (Law of Definite Proportions)
All ______________ of a ______________________have the same
________________________________; or all samples have the _______
______________________________________ by ________________of the
elements present.
Example:
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C. John Dalton and the Atomic Theory of Matter
Explained laws of ____________________________________________________ and
extended them to cover the law of ________________________________________.
Main Ideas of Dalton’s Model
1. All matter consists of _______________________________________ called
______________________.
2. All ______________of a given ______________are ___________but atoms of any one
element are __________________ from the atoms of every other element.
3. ___________________are formed when _____________of different elements unite in
_______________________________________ratios.
4. Chemical _______________involve ___________________________________; no
_____________are created, destroyed or broken apart in a chemical reaction.
According to Dalton, atoms are __________________ and ______________________.
D. Law of Multiple Proportions
A given set of __________________may __________________to produce two or more
different ____________________, each with a ________________________________.
Example:
E. Dalton’s Model of the Atom
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Components of the Atom
A. J.J. Thomson (discovery of electron), 1897
•
First evidence for subatomic particles came from the study of the conduction of
electricity by gases at low pressures
•
Experimented with ________________________________.
•
Thomson known as discoverer of the ____________________ (led to
_________________________________ model of the atom)
B. Robert Millikan and the Oil Drop Experiment (electron charge & mass), 1909
Obtained the ____________on an electron, which coupled with Thomson’s work,
allowed the calculation of the _____________of an electron.
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C. Earnest Rutherford and the Gold Foil Experiment (discovery of nucleus), 1911
•
Bombardment of gold foil with α particles (helium atoms minus their electrons)
•
•
Found that some of the alpha particles were deflected by the foil
Led to the discovery of a region of heavy mass at the center of the atom
a.k.a. the __________________.
Rutherford’s New Atomic Model & Conclusions
1.
2.
3.
Current Atomic Model & Subatomic Particles
1. Protons
•
•
Present in the nucleus
Mass nearly equal to the H atom (1 ______________________________)
2. Neutrons (James Chadwick, 1932)
• Present in the nucleus
• Particles with masses almost identical to protons but with no charge
• Neutrons help disperse the repulsion of positive charges in the nucleus
•
•
More than 99.9% of the atomic mass is concentrated in the nucleus
The volume of the nucleus is much smaller than the volume of the atom
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Summary: Electrons, Protons and Neutrons
Particle
Symbol
Mass
Charge
Location
Identification of an Element via the Periodic Table
A. Atomic symbol, Atomic number, & Mass number
Atomic Symbol =
Mass Number (A) =
Atomic Number (Z) =
Example:
A
Z
X
19 1
9F
B. Isotopes
Isotope –
Ex.)
Example 2.1: Write the atomic symbols for the following species:
a. the isotope of carbon with a mass of 13
b. the nuclear symbol when Z = 92 and the number of neutrons = 146.
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C. Ions
Atoms ___________ electrons to become negative ions (a.k.a. ________________).
Atoms ___________ electrons to become positive ions (a.k.a. _________________).
***Charges are shown to the __________________ of an atomic symbol.
Example 2.2: Write the atomic symbols for the following:
a. a species having 16 protons, 16 neutrons and 18 electrons
b. the phosphide ion (symbol = P) with an overall charge of -3
D. An atomic mass unit (amu) – exactly one-twelfth the mass of a carbon-12 atom
1 u = 1.66054 × 10–24 g
•
The atomic mass of an element is the _________________________________
___________________________________________________________________
___________________________________________________________________
•
•
Atomic mass is a weighted average of the masses of naturally occurring
isotopes.
____________________________ is the percent or fraction of each isotope
found in nature.
Example 2.3: Determine the average atomic mass of magnesium which has three
isotopes with the following masses: 23.98 (78.6%), 24.98 (10.1%), 25.98 (11.3%).
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E. RADIOACTIVITY
• Radioactive isotopes are ______________________
•
•
___________________________________________________
•
Emit other particles and are transformed into other elements
•
Radioactive decay is ____________________________________!
Particles emitted
•
____________________________________________________
•
____________________________________________________
•
____________________________________________________
F. Nuclear stability
•
________________________________________________________________
•
•
For light elements, n/p is approximately 1
For heavier elements, n/p is approximately 1.4/1
The Periodic Table: Elements Organized
A. Know location and description of:
1. Groups or families = ______________________________ on periodic table
o Numbered as ______________
o Group 1 =
o Group 2 =
o Group 17 =
o Group 18 =
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2. Periods or series = _______________________________ on periodic table
o __________ periods total
o First period =
o Second period =
o Etc.
3. Metals, metalloids, nonmetals and their properties
o Metals are located _________________________________________
o Nonmetals are ____________________________________________
Metals –
Metalloids –
Nonmetals –
4. Main group elements –
5. Transition metals –
6. Lanthanides and actinides –
B. Dmitri Mendeleev
C. Henry Moseley
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Molecules and Molecular Compounds
A. Molecule – a group of _______________________________ held together in a
definite shape by __________________________________.
B. Formulas
1. Empirical formula –
2. Molecular formula –
Ex.)
3. Structural formula –
C. Ions: Atoms with a charge
o Cations =
o Anions =
o Polyatomic ion =
D. Ionic Compounds – _______________ and _____________ held together by
_________________________________________
1. Solutions of Ionic Compounds
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
Strong electrolyte

Nonelectrolyte
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Naming & Formula Writing for Ionic Compounds
Charges for Specific Groups of the Periodic Table
Group 1
Group 15
Group 2
Group 16
Group 13
Group 17
Writing Formulas for Binary Ionic Compounds
1. Write both elements as ions with their accompanying charges.
2. Crisscross the charges to make them subscripts.
3. Drop the positive and negative signs once they are subscripts.
Example: magnesium nitride 
Practice!! Write formulas for the following compounds:
Magnesium chloride
Sodium chloride
Calcium bromide
Potassium iodide
Sodium oxide
Writing Formulas for Compounds with Polyatomic Ions
Polyatomic ions – ______________________________________________________
1. Same as writing formulas for binary ionic compounds (see above) but use the charge
of the cation and the polyatomic anion.
2. You may need to use parentheses to prevent confusion!
Example: Barium phosphate
Practice!! Write the formula:
Calcium phosphate
Lithium carbonate
Beryllium bicarbonate
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Writing Formulas with Transition Metals
1. Write the metal’s atomic symbol with the value of the Roman numeral as a positive
charge.
2. Write the value of the anion (or polyatomic ion) with its charge.
3. Crisscross the charges to get your formula.
Example: Lead (IV) hydroxide
Naming Binary Ionic Compounds
1. Take the name of the metal right from the periodic table followed by the name of the
non-metal.
2. Drop the last syllable of the nonmetal and add “–ide” as an ending instead
Example:
NaCl –
Al2O3 –
Practice!! Determine the names for the following compounds:
CaCl2
AlCl3
LiBr
BeO
Ra3N2
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Naming Ionic Compounds with Polyatomic Ions
1. Take the name of the metal from the periodic table.
2. Write the name of the polyatomic ion as the second word.
Examples:
MgSO4
LiNO3
Ba(OH)2
Practice!! Name the compound:
RbNO3
NaHCO3
Mg(OH)2
Naming Compounds with Transition Metals
1. Name the metal from its atomic symbol.
2. Determine the charge on the metal by “uncrossing” the charges on the positive and
negative ions.
3. Write the charge as a roman numeral in parenthesis.
4. Write the name of the anion either as an element with an “–ide” ending or as the
unchanged name of the polyatomic ion.
****Charge of metal =
Examples:
CrCl6
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Fe(OH)2
NiO
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Naming & Formula Writing for Molecular (Covalent) Compounds
Writing Formulas for Molecular Compounds (2 nonmetals bonded together)
1. Write the symbol for the first element listed.
•
If there is a prefix on the first element, write the prefix value as a subscript
attached to the first element’s symbol.
2. Write the symbol for the second element listed
•
Examples:
If the prefix on the second element is “di-” or greater, write the prefix value as a
subscript attached to the second element’s symbol
Prefix
Value
Prefix
Value
Mono-
1
Hexa-
6
Di-
2
Hepta-
7
Tri-
3
Octa-
8
Tetra-
4
Nona-
9
Penta-
5
Deca-
10
Selenium dioxide
Carbon tetrachloride
Nitrogen trihydride
Naming Molecular Compounds (2 nonmetals bonded together)
Given the formula:
1. Write the names of the 2 elements
2. Attach the appropriate Greek prefix (see chart above) to the beginning of the first
element only if it has a subscript greater than or equal to 2.
3. Attach the appropriate Greek prefix to the second element no matter what!
4. Change the ending of the second element’s name to an –ide ending
Examples:
P2O6
CO2
NO
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