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 - It is not destroyed
or created
(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?
5
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
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
Atomic Number
Atomic Mass
Au
# of Electron
# of Neutrons
12
Na
W
# of Protons
184
197
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 #
12
6
Atomic
#
 Hyphen notation: carbon-12
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
18
Determining approximate placement of electrons
Energy Level
MAX. # of electrons
1st
2nd
3rd
4th
Chlorine (atomic #_____)
 # protons = _____
 # electrons = _____
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

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 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
•
•
•
J.J. Thomson
Cathode Ray Experiment
http://www.youtube.com/watch?v=XU8nMKkzbT8
Background
Born in Manchester, England in December
1856
 Studied physics and mathematics
 Won a nobel prize in 1906

Experiment Observations
1.
An object placed between the cathode and
the opposite end of the tube cast a shadow
on the glass.
2.
A paddle wheel placed on rails between the
electrodes rolled along the rails from the
cathode toward the anode.
3.
Cathode rays were deflected by a magnetic
field in the same manner as a wire carrying
electric current, which was known to have
a negative charge.
4.
The rays were deflected away from a
negatively charged object.
Discovery of Electrons-1897
Experiments supported hypothesis that the
particles that compose cathode rays are
negatively charged
 Measured the ratio of cathode-ray particles
to their mass—found it was always the
same
 Concluded that all cathode rays are
composed of identical negatively charged
particles called electrons
 Experiments revealed the electron has a
very large charge for its tiny mass

Lord Rutherford of
Nelson
As flawlessly explained by: Adam, Jane, Justin, Jeremy,
rob
Rutherfordian History




Born 1871 in New
Zealand
In early work,
discovered
radioactive half-life
Had an element
named after himrutherfordium
Became known as the
father of nuclear
physics



Assistants Geiger and
Marsden bombarded a
thin piece of gold foil
with a narrow beam of
alpha particles.
Some of the particles were
redirected by the gold foil
back towards their source.
Rutherford thus concluded
that the force must be
caused by a very densely
packed bundle of matter with
a positive charge, which he
called the nucleus.
Discovery of the Atomic
Nucleus
The Experiment

Rutherford had discovered that the volume of the nucleus
was very small compared to the total volume of the atom,
suggesting that there was a lot of empty space.
6. IONS
IONS cont……
• Ions are _____________________ (or groups of atoms).
• Ions are formed when ______________________.
Ions and Ionic Compounds
 Recall:
Molecules make up:
 Ions make up:
35
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 ___.
◦ The symbol for a chloride ion is Cl1- or just Cl-. (The 1 is ______.)
36
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 ___.

The symbol for a sodium ion is Na1+ or just Na+. (The 1 is
understood.)
37
Ions
◦ Recall: What charge do electrons carry?
 ________
◦ When atoms ______ negative electrons, they form ______ions.
◦ When atoms ______negative electrons, they form _______ ions.
38

List the number of protons, electrons, and neutrons in each ion

◦ O2◦ H+
◦ FDo any of these atoms have complete valence shells?
Do Now

SW

BAT determine the formulas for ionic compounds

SWBAT name different ionic compounds
Objectives
Ionic Compounds
 Oppositely charged ions connect together to form
_____________.
 For example, sodium ions (Na+) connect to chloride ions (Cl-)
to make sodium chloride
(NaCl), or ________.
41
Sodium chloride consists of an equal number of
positive and negative ions arranged in a 3dimensional network called a _________.
A scanning electron micrograph shows the cubic
structure of NaCl crystals.
42
A space-filling model of Nacl provides
information about how the individual sodium
ions & chloride ions are _____________.
What else does this model suggest about the
sodium and chloride ions or sodium
chloride?
43
If an ionic compound dissolves in water, the
individual ions would:
To show that they were now in an aqueous
solution, an _______ would be added after the
symbols for the ions.
Na+(aq)
Cl- (aq)
44
More about Ions
Cation:

Na+,
Anion:

Cl-

Monoatomic ions (or monatomic)

Na+, Cl-, Mg2+, O2-, Al3+, N3-

Polyatomic ions

NH4+, CO32-, SO42-, PO43-


45
Common Ions
 See text p. 40 for a list
of common ions.
46

Find trends on the periodic table
Practice:

Work

sheet # 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.
48
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
50
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.
51
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+
2. PO433. CO324. Al3+

What does the word “ionic” mean?


BrAg+
NH4+
NO3-
 Worksheet (Unit 1B.9 part 3)
Practice:
 Study for quiz