Chapter 3
Chemical Foundations
*Elements, Atoms, and Ions
Title: Aug 30­6:07 PM (1 of 29)
Section 3.1 and 3.2 The Elements
Three uses of the term "Element"
1. Element: A sample of the element large enough to weigh on a balance
2. Element: 1 single atom of an element.
3. Element: A molecule of two or more of the same element bonded together.
How do we represent Elements?
*Element Symbols The first letter of the symbol
is always capitalized. The second letter of the
symbol is always in lower case.
*What is the symbol for each of the following elements?
Title: Sec 3.1 & 3.2 (2 of 29)
Section 3.3 Dalton's Atomic Theory
What are the 5 statements summarized by John Dalton (1766­1844) ?
1. Elements are made of tiny particles called atoms.
2. All atoms of a given element are identical
3. The atoms of a given element are different from
those of any other element
Compounds! Notice the number of atoms of each type in the molecule is represented by a subscript, except when it is 1. (NO, NO2, N2O)
4. Atoms of 1 element can combine with atoms of
other elements to form compounds. A given compound
always has the same relative numbers and types of
atoms.
5. Atoms are indivisible in chemical processes. That is,
atoms are not created or destroyed in chemical reactions.
Title: Sec 3.3 (3 of 29)
Section 3.4 Formulas and Compounds
*Compound 2 or more different elements bonded together
*Chemical Formula shows the type and number of atoms bonded together in a
compound
Let's Practice! Write the formula for each of the following compounds, listing the elements
in the order given.
1. A molecule containing six carbon atoms and six hydrogen atoms.
2. A compound containing one calcium atom and two chlorine atoms.
3. A compound containing one sodium atom, one nitrogen atom, and
three oxygen atoms.
Title: Sec 3.4 (4 of 29)
Section 3.5 Structure of the Atom (History)
I. 2 Models of the Atom
A. J.J. Thomson (1800's)
Information gathered from cathode ray tube (CRT) experiments
led to the discovery of the mass and charge of the electron first.
(1) Electron Characteristics­ a very small particle with a negative
charge
(2) View of Model­ Plum Pudding
*
* Plum Pudding Demo
Cathode Ray Tube Demo
Figure 3.3 Plum Pudding Model
Title: Sec 3.5 (5 of 29)
B. Rutherford's model
Two regions of the atom the nucleus and empty space
(1) Rutherford's gold foil experiment (1909) led to the discovery
of the nucleus.
(2) Nucleus­ the positively charged, dense central portion of the
atom. Contains nearly all the atom's mass but takes up an insignificant
fraction of its volume.
Proton­ positively charged particle nearly 2000 X's (1836)
larger than the mass of an electron, but equal to the negative charge of the
electron. Mass = 1.673 X 10­24grams
Neutron
­ electrically neutral nuclear particles equal in mass to the
proton.
­ discovered by Chadwick.(1932)
­ mass = 1.675 x 10 ­24grams.
http://micro.magnet.fsu.edu/electromag/java/rutherford/
Title: Rutherford (6 of 29)
(3) The nucleus is held together by short range forces called nuclear forces
neutron­neutron forces, proton­proton forces, and neutron­proton forces.
(a) Similar electrically charged particles generally repel one another;
however, up to 100 protons can exist close together in a nucleus when up to
about 150 neutrons are also present.
(b) The relative size of atomic particles ­­the overall size of the atom is 40,000
X's greater than the nucleus!
Title: Sep 12­7:40 PM (7 of 29)
3.6 Modern Concept of Atomic Structure
Particle
Mass Number
Actual Mass
(grams)
Relative charge
Location
Proton
Electron
Neutron
Today's view of the Atom
­Tiny nucleus (about 10­13cm in diameter)
­Nucleus contains protons+ and neutrons0
­Neutron functions to help to hold the protons (which repel each other)
*Why do would protons repel each other?
­Electrons are found outside of the nucleus.
They have the opposite charge of protons
and are much smaller.
*They are important determining chemical properties
***If all atoms are composed of these same components (electrons, protons, and nuetrons),
why do differeent atoms have different chemical properties?
Depends on number and arrangement of electrons!
ANSWER
Title: Sec 3.6 (8 of 29)
• The _______________ an element is the number of ____________ in the nucleus of
each atom of that element.
• The mass number or _______________ is the total number of protons and
__________ in the nucleus.
• Protons = ________________
• Electrons = _________________
• Neutrons = _________________ ­ ________________
Title: Summary (9 of 29)
PRACTICE!!!!
Title: Practice (10 of 29)
Section 3.7 Isotopes
Isotope­ atoms with same number of prtons but different number of neutrons
*Behave the same chemically because not changing the electron # or
arrangement!
Atomic Number­ # of protons in a nucleus
Mass Number­ Sum of protons and nuetrons in an atom's nucleus
Title: Sec 3.7 (11 of 29)
A
Z
X
X = symbol of the element
A = the mass number (sum of p + n)
Z = the atomic number (number of p)
Where is almost all the mass in an atom? ______________
If mass number is the sum of the protons and neutrons...How do you calculate the number
of neutrons?
(A ­ Z) = # of Neutrons
or
(Mass # ­ ANSWER
Atomic number ) = # of Neutrons
Title: Sep 13­2:04 PM (12 of 29)
Nuclear
Notation
1
Protons
Electrons
Neutrons
106Pd
42
S­33
2
54
3
4
78
132Cs
55
5
40
31
Kr­84
6
7
___Ba
83
56
40
8
9
10
Hyphen
Notation
___ ­92
235
92 U
Cf
Title: Sep 17­7:08 PM (13 of 29)
158
• Isotopes are atoms of the same element with different masses.
• The number of protons in the nucleus determines the identity of an atom. For example, all hydrogen atoms contain only one proton. • An atom that contains more than one proton in its nucleus is an atom of an element other than hydrogen. Hydrogen atoms, like those of all naturally occurring elements, contain varying numbers of neutrons.
• The most common type of hydrogen isotope has one proton only. It is sometimes called Protium. Protium makes up 99.985% of naturally occurring hydrogen.
• A deuterium atoms contains one proton and one neutron. The third form of hydrogen is known as tritium, which is radioactive. It contains one proton, and two neutrons.
Title: Sep 14­9:57 PM (14 of 29)
Isotopes and Average Atomic Mass
Elements come in a variety of isotopes, meaning they are made of atoms with the same
atomic number but different atomic masses. These atoms differ in the number of neutrons.
The average atomic mass is the weighted average of all the isotopes of an element
EXAMPLE: A sample of cesium is 75% 133Cs, 20% 132Cs, and 5% 134Cs.
What is its average atomic mass
Title: Calc Average Atomic Mass (15 of 29)
Isotopes and Average Atomic Mass
Elements come in a variety of isotopes, meaning they are made up of atoms with the sme atomic number but different atomic masses. These atoms differ in the number of neutrons.
The average atomic mass is the weighted average of all the isotopes of an element.
Determine the average atomic mass of the following mixtures of isotopes.
1.
80% 127I, 17% 126I, 3% 128I
2.
50% 197Au, 50% 198Au
3.
15% 55Fe, 85% 56Fe
4.
99% 1H, 0.8% 2H, 0.2% 3H
5.
95% 14N, 3% 15N, 2% 16N
6.
98% 12C, 2% 14C
Title: Sep 17­8:10 PM (16 of 29)
Questions: ­­­­_____ 1. How many neutrons does Zn­66 (atomic number 30) have?
_____ 2. Ag­109 has 62 neutrons. How many electrons does the neutral
atom have?
3.
An atom of chlorine has an atomic number of 17 and a mass number of 35. How many protons, electrons and neutrons does it have?
____P
____E
____N
_____ 4. How many electrons does scandium (Sc) have?
_____ 5. How many protons does tungsten (W) have?
_____ 6. How many neutrons does Einsteinium­254 (Es­254) have?
_____ 7. How many average neutrons does platinum (Pt) have?
_____ 8. How many protons does arsenic­75 (As­75) have?
_____ 9. How many neutrons does krypton­85 (Kr­85) have?
_____ 10. How many electrons does titanium (Ti) have?
_____ 11. How many protons does radon (Rn) have?
_____ 12. Give the hyphen notation for this atom:
p = 76 e = 76 n = 116
_____ 13. Give the nuclear symbol notation for this atom:
p = 11 e = 11 n =11
14. What is the relationship between an atom containing 4 protons, 4 electrons and 5 neutrons and one containing 5 protons, 5 electrons, and 4 neutrons?
15. What is the relationship between an atom containing 7 protons, 7 electrons and 8 neutrons and one containing 7 protons, 7 electrons, and 7 neutrons?
16. According to the Periodic Chart of the Elements, which element listed has an average of 58 neutrons?
Title: Sep 17­8:11 PM (17 of 29)
Periodic Table Structure
Mendeleev
*Developed one of the first periodic tables
and arranged it according to increasing
atomic mass
In the periodic table the horizontal rows are called ____________ and the vertical columns are called ___________or _____________. The _____________ have 2 different sets of numbers assigned to them. Elements in the same _____________ display similar _________________. Some of these groups have special names in addition to their_____________, such as ____________ metals, _________ __________ metals, _________________ and _________
or ___________ gases.
The periodic table is arranged according to increasing _________ _________. The periodic table is also made up of 4 _____________. The blocks are grouped according to which ______________ is filled last. All elements can be divided into 3 groups: ____________, ________________, and _______________________. These groupings are made according to ________________ and ________________ in the periodic table.
http://www.privatehand.com/flash/elements.html
Title: Sep 17­7:51 PM (18 of 29)
color the metals red, the nonmetals yellow, and the metalloids orange. All elements must be colored!
Title: Sep 17­8:31 PM (19 of 29)
List the properties of the following:
Metals (p. 65)
•
•
•
•
Great conductors (of heat & electricity)
Malleable
Ductile
Lustruous (shiny)
Nonmetals
• Often gases or dull, brittle solids
• Low melting points
• Found to the Right of the Staircase
O
O
C
• Forms compounds with metals (NaCl, CaF2)
• Combines with other nonmetals to form diatomics (O2, N2, H2)
N
Cl
Metalloids
• Have characteristics of both metals and nonmetals
• border between metals and nonmetals
• semiconductors of electricity
Alkali Metals
*Most reactive metals
*Very soft
*Not found in nature in element form because they are so reactive
http://chemed.chem.purdue.edu/demos/main_pages/9.1.html
Alkaline Earth Metals
*Very reactive metals
*Harder than alkali metals
*Still too reactive to be found in nature as an element
Transition Metals
*Typical Metals
Lanthanides and Actinides
Halogens
Lanthanides ­ called rare earth elements (actually not rare). They're shiny reactive metals.
Actinides ­ unstable, radioactive elements. Many of these elements are man­made
*Most reactive nonmetals
F
Noble Gases
*A group of nonreactive gases.
Ar
He
Kr
Title: Sep 17­8:39 PM (20 of 29)
Sb
Te
3.9 Natural States of Elements
Typically we do NOT find elements in pure form (uncombined with other elements).
Normally they form compounds readily!
What are a few that we have found in pure form?
•
Gold (Au)
NOBLE ELEMENTS •
Platinum (Pt)
•
Silver (Ag)
•
Group 8 Elements (He, Ne, Ar, Kr, Xe, Rn)
• What are Diatomic Molecules?
• Solid Elements
• Liquid Elements
• Gas Elements
Title: Sep 18­1:42 PM (21 of 29)
Title: Sep 17­8:35 PM (22 of 29)
3.10 Ions
Ion definition­ an element or group of elements with a charge
Cation­ a positive ion
Anion­ a negative ion
Title: Sep 18­3:27 PM (23 of 29)
If the atom has a charge, electrons = protons ­ charge.
Title: Sep 18­3:30 PM (24 of 29)
http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA0/Movies/NACL1.html
Title: Sep 18­3:34 PM (25 of 29)
Complete the following chart
Elements to be combined
Magnesium
Fluorine
Aluminum
Bromine
Potassium
Sulfur
Sodium
Chlorine
Boron
Nitrogen
Beryllium
Phosphorus
Aluminum
Oxygen
Calcium
Sulfur
Title: Sep 18­3:35 PM (26 of 29)
Criss­Cross
Balanced Formula
Title: Jul 17­2:33 PM (27 of 29)
Bingo Words
anion
Atom
Atomic Number
Cation
Isotope
Neutron
Nucleus
Proton
Chemical Formula
Compound
Electron
Ion
Metal
Nonmetal
Mass Number
Nuclear Force
uc
Title: Sep 21­12:58 PM (28 of 29)
Element
Atom/Ion
Calcium atom
Fluorine ion
Barium Ion
Symbol
40
Ca
20
19
9 F­
Ba2+
Aluminum Ion
CarbonAtom
Sulfur Atom
Chromium Ion
Oxygen Ion
Al3+
13C
6
32 S
16
52
Cr2+
24
16
8
O2­
Title: Sep 21­1:43 PM (29 of 29)
Atomic
Number
# of Protons
# of Neutrons
mass # of #
electrons
Charge
20
20
20
40
20
0
9
9
10
19
10
1­
56
56
81
137
56 2+
13
13
14
27
10 3+
6
6
7
13
6
0
16
16
16
32
16
0
24
24
28
52
22
2+
8
8
8
16
10
2­
Attachments
role of neutrons
Element Quiz
Cathode movie
rutherford
Element song
Sodium and chlorine reaction
Rutherford 2