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Zumdahl DeCoste
World of
CHEMISTRY
Chapter 3
Chemical
Foundations:
Elements,
Atoms, and
Ions
Top Ten
3
 An
ELEMENT is the simplest form of a
substance that can not be broken
down.
A
COMPOUNDis two or more
elements bound together.
 Presently
there are 115 elements,
88 of which occur naturally.
Table 3.1
5
The 9 elements that account for 98% of the
earths total mass (table 3.1)
 Oxygen
 sodium
 Silicon
 potassium
 Aluminum
 magnesium

Iron

calcium

hydrogen




Names of the elements originated mainly
from GREEK. LATIN, and GERMAN.
We abbreviate the elements to simplify.
Always us a CAPITAL letter for the first
letter in element.
Use lower case if there is a second
letter.
– Ex: Hydrogen = H
– Gold = Au
(Aurum is latin for shiny)
Table 3.3
8
Dalton's Atomic Theory
1.Elements are made of tiny particles called
atoms
2. All atoms of a given element are identical
3.Atoms of a given element are different from
those of any other element.
4.Atoms of one can combine with atoms of
another to form compounds
5.Atoms are indivisible in chemical processes,
they are not created or destroyed.
Rules for Writing Formulas
1.Each atom present is represented
by its element symbol.
2.The number of each type of atom is
indicated by a subscript written to
the right of the element symbol.
3.When only one atom of a given
type is present, the subscript 1 is
not written.
Copyright© by Houghton Mifflin
Company. All rights reserved.
10
Atomic Discoveries



J.J Thomson concluded that all atoms contain
negative particles called electrons and must then
also contain positive particles called protons.
William Thompson was for the PLUMPUDDING model. He said the atom was like
plum pudding ( bowl of pudding with things
floating in it). Atom has pudding of positive and
negative charges scattered around to counter
balance.
Rutherford found that atoms must have a
nucleus with a dense postive charge. He
concluded that the nucleus contains protons,
which are positive charge, and also neutrons
which have no charge.
Figure 3.3: Plum Pudding model
of an atom.
12
Figure 3.5: Rutherford’s
experiment.
13
Figure 3.6: Results of foil
experiment if Plum Pudding
model had been correct.
14
Figure 3.6: Actual Results.
15
Atoms can be divided into 3 subatomic Particles:
1. Protons
Particle
2. Neutrons
3. Electrons
Symbol
Charge
Mass
location
Proton
p
+
1
nucleus
Neutron
n
0
1
Nucleus
Electron
e
-
1/1800 orbitals
Figure 3.9: A nuclear atom
viewed in cross section.
18
Figure 3.10: Two isotopes of
sodium.
19
ATOMIC NUMBER means the number of protons in an
element
MASS NUMBER means the number of Neutrons and
Protons in the element
23
11
Na
23 = mass number
= protons + neutrons
11 = atomic number
Isotopes
 Isotopes
are atoms of the same
element that have different numbers
of neutrons.
 Isotopes
have the same atomic
number, but different mass number
Ion: an element, or atom with a
charge
Charged because of movement or transfer
of electrons
 Cation: positive ion, electrons are lost
(example: Mg2+)


Anion: negative ion, electrons are gained
(example: Cl-)
Charges are represented with superscript
 Ionic compounds contain metal & nonmetal – net charge equals zero

Figure 3.19: The ions formed
by selected members of
groups 1, 2, 3, 6, and 7.
23
Figure 3.20: Pure water does
not conduct a current.
24
Figure 3.20: Water containing
dissolved salt conducts a current.
25
The Periodic Table
The known elements were organized
according to their atomic masses in 1871
by MENDELEEV.
 The modern version of his table is called
THE PERIODIC TABLE OF the ELEMENTS
 The Horizontal rows are called PERIODS
 The vertical columns are called GROUPS
 The Main Group Elements are in groups
1,2,13,14,15,16,17,and 18
 Transition Metals are elements in groups
3-12

The periodic table.
27
All Elements can be divided into
three main categories:

Metals

Nonmetals

Metalloids
Elements classified as metals
and nonmetals.
29
Most of the elements are METALS and are located on the LEFT side
of the Periodic Table and include the Lanthanides and Actinides.
Properties of Metals:
1. Good conductors of HEAT and ELECTRICITY
2. Have Metallic Luster (shiny and reflect light well)
3. Are Malleable (can be hammered into thin sheets)
4. are Ductile (can be drawn into wires)
•All metals , except Hg (mercury) are solid at room temperature, 25 °
C.
The upper right hand corner of the Table is where the NONMETALS are found, including Hydrogen
Properties of NONMETALS:
1. poor conductors of HEAT and ELECTRICITY
2. Do Not have a shiny appearance or reflect light well
3. are brittle in the solid form
The Metalloids are the 6 elements:
B, Si, Ge, As, Sb, and Te
* sometimes called semi-metals
-They separate the metals and non-metals and be found hugging the
staircase line.
-Properties:
-1. poor conductors of heat
-2. semi-conductors of electricity
-3. have a dull appearance and do not reflect light as well
-4. are brittle solids at 25° C.
Silicon computer chip
The most
important
metalloid is
silicon – it’s
used to
make
computer
chips
Group 1 Elements are also called ALKALI METALS
Examples are: Li, Na, K, Rb, Cs, and Fr.
Group 2 Elements are ALKALINE EARTH METALS
Examples are: Be, Mg, Ca, Sr, Ba, and Ra
Group 17 Elements are called the HALOGENS
Examples are F, Cl, Br, I, A
Group 18 elements are called NOBLE GASES (or inert
gases, or rare gases)
Examples are : He, Ne, Ar, Kr, Xe, Rn
ALKALI METALS
- are very Reactive, which means they readily
combine with other elements.
** React with chlorine gas to form a metal chloride
** React with water to form hydrogen gas
ALKALINE EARTH METALS
- they are reactive, but not as reactive as the alkali metals.
** react with chlorine gas to form a metal chloride
** react with water to form hydrogen gas
(sodium reacts with water at room temperature, but
magnesium won’t react with water unless the water is
boiling.)
Alkali Metals and Alkaline Earth Metal have been used in
everyday items such as:
*Lithium was used to treat manic depression
-7-UP used to contain lithium
*Magnesium is used in disposable flash bulbs
*Calcium can be found in limestone, chalk, marble, and
coral.
The Halogens
* are non-metals and exist as diatomic molecules ( a molecule that
contains 2 atoms.
- Homonuclear diatomic molecules are the same element
F2, Cl2, Br2, and I2
-Heteronuclear diatomic molecules are different elements:
CO, NO,
Halogens are reactive and react with Hydrogen gas to form
compounds with the formula (HX)
Ex. -HF is used to etch glass (lightbulbs, TV tubes)
-HCl is used to digest food
Nitrogen gas contains NXN
molecules.
41
Oxygen gas contains OXO
molecules.
42
Noble Gases:
- They are all colorless gases at 25°C.
- They are unreactive (very stable)
Ex: Neon, used in neon signs (zapped by electricity)
A collection of argon atoms.
44
Table 3.5
45
Figure 3.15: The
decomposition of two water
molecules.
46
Terms to Know:
Melting Point: goes from solid to liquid
Freezing point: goes from liquid to solid
Evaporation:
Condensation:
goes from liquid to gas
goes from gas to liquid
Sublimation: goes from solid to gas
Deposition:
goes from gas to solid