4. ATOMIC STRUCTURE
History – ancient Greeks
Democritus – (460-370 B.C.)
• Matter is composed of atoms – moving around in empty space
• Atoms are solid homogeneous, indestructible and indivisible
• Different size and shape
• Size shape & movement determine the properties of matter
Aristotle – ( 384 322 B.C.)
• Empty space cannot exist
• Matter is made of earth, fire air and water
Daltons Atomic Theory
• John Dalton (1766-1844)
• Matter is composed of extremely small particles called atoms
• Atoms are indivisible and indestructible
• Atoms of a given element are identical in size, mass and chemical properties
• Atoms of a specific elements are different from those of another element
• Different atoms combine in simple whole number ratios to form compounds
• In a chemical reaction, atoms are separated, combined and rearranged
Conservation of mass
Remember – Law of Conservation of mass
states that mass is
conserved -
(Atoms separate, combine or rearrange – Dalton)
RUBBING A BALLOON AGAINST YOUR HAIR RESULTS
IN STATIC ELECTRICITY.
CLOTHES TAKEN OUT OF THE DRIER OFTEN SHOW
STATIC CLING.
THE SHOCK THAT YOU SOMETIMES RECEIVE AFTER
YOU WALK ACROSS A RUG & TOUCH A DOORKNOB IS
ANOTHER EXAMPLE OF MATTER’S ELECTRICAL
NATURE.
Static cling is best seen
when the humidity is low.
WHAT CAUSES THESE PHENOMENA?
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ATTRACTION & REPULSION
• The electrical properties of matter can be summarized as follows:
• What are these positive and negative particles?
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What is an Atom?
• The smallest particle of an element that retains the properties of an element
consists of
• PROTONS
• NEUTRONS
• ELECTRONS
Parts of the Atom
ProtonIn nucleus, positive charge and a mass of 1
NeutronIn nucleus, neutral charge and a mass of 1
ElectronOutside nucleus, negative charge
and no mass
Complete the chart
Part of Atom
Proton
Neutron
Electron
Charge
Mass
How do Atoms Differ?
• The number of Protons identifies it as an atom of a particular element
• Atoms are Neutral so the number of Protons (P) Equals
the number of Electron (E) or P = E
How do Atoms differ cont…
•
Atomic Number = The number of Protons
= The number of Electrons
Mass Number is the Atomic Number (Protons)
PLUS number of Neutrons (NOT on the Periodic Table!)
Mass Number = P + N
How do Atoms differ cont…
Every neutral (uncharged) atoms contains an equal number of
positively charged protons (+) and negatively charged (-) electrons.
# of (+) protons = # of (-) electrons
Positive-Negative attractions between the protons in one atoms the electrons
in another atom hold atoms together in bonds.
DO NOW:
Element Name
Na
W
Au
Atomic Number
Atomic Mass
# of Protons
# of Electron
# of Neutrons
ISOTOPES
Isotopes - Atoms of the same element have same
number of protons BUT different
number of Neutron
EX:
Copper has two isotopes :
Cu 29 protons & 34 Neutrons (Cu - 63)
Cu 29 Protons & 36 Neutrons (Cu - 65)
ISOTOPES
• Atoms of the same element with different mass numbers.
 Nuclear symbol:
Mass #
Atomic #
 Hyphen notation: carbon-12
12
6
C
ISOTOPES
© Addison-Wesley Publishing Company, Inc.
5. ELECTRONS
Lets Look at ELECTRONS
•
•
•
•
Found orbiting outside of the nucleus
Electrons found at different energy levels
Outer most electrons are called Valence Electron
Valence Electrons determine the chemical properties
of an element
LEWIS DOT STRUCTURE
Valence Electrons: outermost electrons
Electron Configuration:
Energy Level
MAX. # of electrons
1st
2
2nd
8
3rd
8
4th
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DETERMINING APPROXIMATE PLACEMENT OF ELECTRONS
Energy Level
MAX. # of electrons
1st
2nd
3rd
4th
Chlorine (atomic #_____)
Outermost energy level: _________
• # protons = _____
# of valence electrons: __________
• # electrons = _____
LEWIS DOT STRUCTURE:
PRACTICE:
Draw the Lewis Dot Diagrams for the following Atoms:
• Ca
• Li
• F
• Worksheet: Unit 1 B.9 Valence Electrons
6. IONS
IONS AND IONIC COMPOUNDS
• Recall: Molecules make up one kind of compound.
• Ions make up another kind of compound.
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IONS cont……
• Ions are electrically charged atoms (or groups of atoms).
• Ions are formed when neutral atoms gain or lose electrons.
IONS
• Recall: What charge do electrons carry?
• Negative
• When atoms gain negative electrons, they form negative ions.
• When atoms lose negative electrons, they form positive ions.
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IONS
• For example, sodium (Na) is # 11 on the Periodic Table.
• It has 11 (+) protons and 11 (-) electrons.
• If it lost 1 (-) electron, it would have 11 (+) protons and 10 (-) electrons.
• It has one more proton than electrons, so it has a charge of -1.
• The symbol for a sodium ion is Na1+ or just Na+. (The 1 is understood.)
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IONS
• For another example, chlorine (Cl) is # 17 on the Periodic Table.
• It has 17 (+) protons and 17 (-) electrons.
• If it gained 1 (-) electron, it would have 17 (+) protons and 18 (-) electrons.
• It has one less proton than electrons, so it has a charge of +1.
• The symbol for a chloride ion is Cl1- or just Cl-. (The 1 is understood.)
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DO NOW
• List the number of protons, electrons, and neutrons in each ion
• O2• H+
• F-
• Do any of these atoms have complete valence shells?
OBJECTIVES
• SWBAT determine the formulas for ionic
compounds
• SWBAT name different ionic compounds
IONIC COMPOUNDS
• Oppositely charged ions connect together to form ionic
compounds.
• For example, sodium ions (Na+) connect to chloride ions (Cl-)
to make sodium chloride
(NaCl), or table salt.
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SODIUM CHLORIDE CONSISTS OF AN EQUAL
NUMBER OF POSITIVE AND NEGATIVE IONS
ARRANGED IN A 3-DIMENSIONAL NETWORK
CALLED A CRYSTAL.
A scanning electron micrograph shows the cubic
structure of NaCl crystals.
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A SPACE-FILLING MODEL OF NACL PROVIDES
INFORMATION ABOUT HOW THE INDIVIDUAL
SODIUM IONS & CHLORIDE IONS ARE ARRANGED
WITHIN THE SALT CRYSTAL.
What else does this model suggest
about the
sodium and chloride ions or sodium chloride?
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IF AN IONIC COMPOUND DISSOLVES IN WATER, THE
INDIVIDUAL IONS WOULD SEPARATE FROM EACH
OTHER AND SPREAD OUT THROUGHOUT THE
WATER.
TO SHOW THAT THEY WERE NOW IN AN AQUEOUS
SOLUTION, AN (AQ) WOULD BE ADDED AFTER THE
SYMBOLS FOR THE IONS.
NA+(AQ)
CL- (AQ)
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MORE ABOUT IONS
• Cation – positive ion
• Anion – negative ion
• Monoatomic ions (or monatomic)
• Polyatomic ions
• Na+,
• Cl• Na+, Cl-, Mg2+, O2-, Al3+, N3-
• NH4+, CO32-, SO42-, PO4335
COMMON IONS
• See text p. 40 for a list
of common ions.
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PRACTICE:
• Find trends on the periodic table
• Worksheet # Unit 1 B.9 part 2 Lewis Dot
Structures
FORMULAS FOR IONIC COMPOUNDS
• 2 Rules for Writing Formulas for Ionic Compounds
• 1. Cation first, then anion
• 2. Correct formula will be neutral, with the fewest number of each ion needed to make
the total electrical charge zero
• No charges are shown in the formula.
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PRACTICE PROBLEMS
• NaCl
• One Na1+ and one Cl1- cancel each other out.
• +1 + -1 = 0
• CaCl2
• One Ca2+ needs two of the Cl1- to cancel it out.
• +2 + -1 + -1 = 0
Note: Negative monoatomic ions
change their ending to “ide.”
Examples above are sodium
chloride and calcium chloride.
FORMULAS CONTAINING POLYATOMIC IONS
• Formulas for compounds containing polyatomic ions follow the same rules
• If a subscript is needed, it follows the entire polyatomic ion, which is enclosed in
parentheses
• For example, the calcium ion has a +2 charge, and the nitrate ion has a -1
charge
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FORMULAS CONTAINING POLYATOMIC IONS
• For example, the calcium ion has a +2 charge (Ca2+),
• and the nitrate ion has a -1 charge (NO31+).
•
• Two nitrate ions are needed to balance out the charge on one calcium ion.
• The formula for calcium nitrate is: Ca(NO3)2.
No charges are shown in the formula.
• Polyatomic ions do not change their endings.
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NAMING IONIC COMPOUNDS
• 1. Name the cation, then the anion
• 2. Have the last few letters changed to –ide (monoatomic ions only)
• Ex. KF, potassium fluoride
• Ex. Ca(NO3)2, calcium nitrate
• Practice Worksheet Unit 1B.9 & B.10 Ion supplement
TRY THIS…
• Write the formula and name the following ionic compounds
• 1. Ca2+
Br-
• 2. PO43- Ag+
• 3. CO32- NH4+
• 4. Al3+
NO3-
• What does the word “ionic” mean?
PRACTICE:
• Worksheet (Unit 1B.9 part 3)
• Study for quiz