Transcript Chapter 4 Chemical Foundations: Elements, Atoms, and Ions

Dalton’s Atomic Theory
1. Elements are made of tiny particles called atoms.
2. All atoms of a given element are identical (not exactly;
isotopes)
3. The atoms of a given element are different from those of any
other element.
4. Atoms of one 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. A
chemical reaction simply changes the way the atoms are
grouped together.
Laws of Chemical
Combination
Law of Definite Proportions: Different samples of the same
compound always contain its constituent elements in the
same proportions by mass
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This is also called the Law of Constant Composition
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Suppose we analyze samples of water from different
sources
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We will find in each sample the same ratio by mass of hydrogen to
oxygen.
So…
 A 10.0 gram sample of water, H2O, is
comprised of 8.9 grams oxygen and 1.1
grams hydrogen.
 Thus, a 100.0 gram sample of water, is
comprised of 89.0 grams of oxygen and 11.0
grams of hydrogen.
Laws of Chemical
Combination
Law of Multiple Proportions (or, Dalton’s Law): If two
elements can combine to form more than one compound,
then the masses of one element that combine with a fixed
mass of the other element are in the ratios of small whole
numbers
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For instance, the atom carbon forms two stable compounds
with the atom oxygen:
Carbon Monoxide (C1O1) and Carbon Dioxide (C1O2)
Neither C1.2O1.3 nor C1.2O2.2, respectively
The Structure of the Atom
Atom: The basic unit of an element that can
enter into chemical combination.
They are made of even smaller particles called
subatomic particles.
Electrons
Protons
Neutrons
Summary of the
Structure of the Atom
Mass and Charge of Subatomic Particles
Particle
Electron
Mass (grams)
9.1095 x 10-28
Charge
-1
Proton
1.67252 x 10-24
+1
Neutron
1.67495 x 10-24
0
Isotopes
Let us modify Dalton’s Atomic Theory.
Isotopes: Atoms having the same atomic number but different
mass numbers.
Atomic Number: The number of protons in the nucleus of an
atom.
Mass Number: The total number of neutrons and protons
present in the nucleus of an atom.
Isotopes
We use the symbol to represent the isotope.
Where X = the symbol of the element
A = the mass number
Z = the atomic number
How do we calculate the number of neutrons?
Mass Number = Number of Protons + Number of Neutrons
Number of neutrons = A - Z
Isotopes
Example
Give the number of protons, neutrons, and electrons in
Strontium-90.
Example
Give the number of protons, neutrons, and electrons in
Mercury-201.
Example
Give the symbol for the phosphorous atom that contains 17
neutrons.
The mole
 Mole = amt that contains as many
“things” as there are atoms of 12 g of C12
 1 mole = 6.022 x 1023 particles
 Molar mass (MM) = mass in grams per 1
mole of particle (g/mol)
Introduction to the Periodic
Table
How to interpret the PT
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Why the symbols?
Why the numbers?
Why the columns?
Why the rows?
Introduction to the Periodic
Table
Groups: The elements in a vertical column of the periodic table.
Period: The elements in each horizontal row of the periodic
table.
Alkali Metals: The Group 1A elements (Li,Na,K,Rb,Cs,Fr).
Alkaline Earth Metals: The Group 2A elements
(Be,Mg,Ca,Sr,Ba,Ra).
Halogens: The nonmetallic elements in Group 7A
(F,Cl,Br,I,At).
Noble Gases: The nonmetallic elements in Group 8A
(He,Ne,Ar,Kr,Xe,Rn).
Transition Metals: Group of elements in the middle of the
periodic table.
Introduction to the Periodic
Table
Elements can be divided into 3 categories: Metals, Nonmetals,
Metalloids
Metal: Good Conductor of heat and electricity.
Physical Properties of Metals
1. Efficient conduction of heat and electricity
2. Malleability (they can be hammered into thin sheets)
3. Ductility (they can be pulled into wires)
4. A lustrous (shiny) appearance
Example
Lithium, Magnesium, Chromium, Gold, and many others.
Introduction to the Periodic
Table
Nonmetals: Usually a poor conductor of heat and electricity,
and it has more varied physical properties than a metal.
They appear in the upper right-hand corner of the periodic
table.
Example
Nitrogen, Oxygen, Bromine, Carbon, Phosphorous, Sulfur, and
many others
Metalloids: or Semimetals have properties that fall between
those of metals and nonmetals
Example
Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium,
Polonium, Astatine
Introduction to the Periodic
Table
Give the symbol and atomic number for each of the elements.
Determine whether the element is a metal or a nonmetal.
Also, determine what family it belongs to.
(a) Argon
(b) Chlorine
(c) Barium
(d) Cesium
Natural States of the
Elements
Noble Metals: Unreactive metals (Au, Ag, Pt).
Noble Gases: The nonmetallic elements in Group 8A (He, Ne,
Ar, Kr, Xe, Rn).
Diatomic Molecule: A molecule that consists of two atoms (N2,
O2, H2, F2, Cl2, Br2, I2).
The diatomic molecules (H2,N2,O2,F2,Cl2) are gaseous in their
elemental forms at normal temperatures. Br2 and Hg are
liquids in their elemental forms at normal temperatures.
Natural States of the
Elements
Allotropes: Two or more forms of the same element that differ
significantly in chemical and physical properties.
Example
Diamond, Graphite, Buckyball