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.

WHAT CAUSES THESE PHENOMENA?Static cling is best seen when the humidity is low.

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ATTRACTION & REPULSION

• The electrical properties of matter can be summarized as follows:

• What are these positive and negative particles?

6

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

Proton- In nucleus, positive charge and a mass of 1

Neutron-In nucleus, neutral charge and a mass of 1

Electron-Outside nucleus, negative charge and no mass

Complete the chart

Part of Atom Charge Mass

Proton

Neutron

Electron

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

Atomic Number

Atomic Mass

# of Protons

# of Electron

# of Neutrons

Na

W

Au

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.

C126Mass #

Atomic #

¨ Nuclear symbol:

¨ Hyphen notation: carbon-12

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 18

DETERMINING APPROXIMATE PLACEMENT OF ELECTRONS

Chlorine (atomic #_____)

• # protons = _____

• # electrons = _____

Energy Level MAX. # of electrons

1st

2nd

3rd

4th

Outermost energy level: _________

# of valence 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. 26

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.) 28

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.31

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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• Na+,

• Cl-

• Na+, Cl-, Mg2+, O2-, Al3+, N3-

• NH4+, CO3

2-, SO42-, PO4

3-

• Cation – positive ion

• Anion – negative ion

• Monoatomic ions (or monatomic)

• Polyatomic ions

MORE ABOUT IONS

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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.41

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