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Introduction to Chemistry
Chapter 2
Section 2.1
Click Here to Play the Element Song!
Chemistry is the Study of
Matter
Matter is a substance: that has mass and occupies space!
All matter has two properties:
_______________ which is a measure of the amount of material in a substance, and
_______________ which is the amount of space an object occupies.
mass
volume
Weight is a measure of the force of gravity.
All matter is composed of simple substances that cannot be broken down by ordinary chemical means called elements.
To date, there are 118 elements.Not all are naturally occuring.
Elements are given symbols that contain . If the symbol has just one letter, it is capitalized. For example:
If the symbol has two letters, only the first is capitalized, the second is written in lower case.For example:
C
He
one, two, or three letters
Take a Moment or Two:
• List everything you know about atoms, elements, compounds, and mixtures.– You may want to use a chart to keep yourself
organized.
• Give three or four examples of each.
An __________________ is the smallest part of an element that has all the properties of that element.
atom
Atoms are composed of three types of particles:
amu = atomic mass unit
Particle Location Charge Mass Relative Mass
Proton Nucleus + 1.67 x 10-24g 1amu
Neutron Nucleus 0 1.67 x 10-24g 1amu
Electron Outside - 9.11 x 10-28 g 0 amuNucleus
Electrons can be found at any location away from the nucleus, but they are more likely to be in certainregions than in others. The regions in space in which it is likely to find electrons are known as
energy levels or orbitals.
Atoms tend to be most stable when their outer energy level contains eight electrons.
Atoms _______________electrons in an attempt to obtain eight outer (or valence) electrons.
gain, lose or share
Elements may combine chemically to form ___________. compounds
A ___________ is the smallest part of a compound that has all the properties of thatcompound.
molecule
A ___________ is a physical combination of two or more substances, each of whichretains its individual properties.
mixture
Compounds differ from mixtures in the following ways:
Compounds Mixtures
New PropertiesSubstances Keep Original Properties
Separated Chemically Separated Physically
Proportions Fixed Proportions Vary
Examples????
The number of protons in an element is indicated by the ______________,
which is given the symbol Z.
Z
atomic number
In neutral atoms, the number of electrons is equal to the number of protons.
________________, which is given the symbol A, is equal to the number of protons plus the number of neutrons.
Atomic mass
A
The number of neutrons is thus the atomic mass minus the atomic number.
Atomic Mass rounded to whole #
Atomic Number - 27
# of Neutrons
Atomic Mass 58.933 = 59
59
32
Atomic Mass Rounded Off
Example: Lithium
Atomic mass
Number of protons
Number of electrons
Number of neutrons
Complete Symbol:3Atomic number
7 amu
3
3
4
Li73
atomic mass
atomic number
Remember! Atomic mass – Atomic number = # Neutrons
IsotopesForms of an element that have the same number of protons, and electrons, but different numbers of neutrons and different masses are called ____________ .isotopesFor example: Hydrogen has three common isotopes
H11 Protium H
21 Deuterium
H31 Tritium - Which is Radioactive!
Your Turn. Complete the ChartIsotope Symbol
Atomic Number
Atomic Mass
Mass Number
Protons Neutrons Electrons
12 13
31 15
35 45
92 238.029
40 51
5525Mn
146C
Ions
A charged particle is called a(n) _______ .
Ions are formed by the gain or the loss of __________ .
ion
electrons
Positive IonsIf an atom loses electrons, it has fewer negative charges than it has positive charges, and thus becomes a ___________ charged particle, known as a _______ . Metals, found on the _____ side of the periodic table, tend to form positive ions.
positivelycation
left
Positive Ions
Left Side of Table
Negative Ions
If an atom gains electrons, it has more negative charges than it has positive charges, and thus becomes a ___________ charged particle, known as a _______ . Nonmetals, found on the _____ side of the periodic table, tend to form negative ions.
negativelyanions
right
Negative Ions
Right Side of Table
Example: Sodium (Na) Ion – Loses one electron
Sodium Atom Sodium Ion
# of Protons
# of electrons
symbol
11 11
11 10
Na0Na+1
Na+or
Na1+or Na
Example: Sulfur (S) Ion – Gains two electron
Sulfur Atom Sulfur Ion
# of Protons
# of electrons
symbol
16 16
16 18
S0 S-2 or S2-
Your Turn….Isotope Symbol
Atomic Number
Atomic Mass
Mass Number
Protons Neutrons Electrons
13 14 12
55.847 26 23
53 74 54
8 16 8
35 -117Cl
Chemical Bonding
A chemical _______ is a force that holds atoms together in compounds. There are two major types of chemical bonds:
bond
Chemical Bonding
In _______ bonds, electrons are transferred from a metal, which loses electrons, to a nonmetal, which gains electrons. The resulting ions have opposite electrical charges, and are strongly attracted to one another.
ionic
Example of Ionic Bonding
F Li
LiF
Example of Ionic Bonding
F-1 Li +1
lost 1 electrongained 1 electronnow 10 electrons now 2 electrons
LiF
A Demo and A Movie
• The demo—
NaHCO3 + HC2H3O2
• One I’m not allowed to do in school…Sodium and Water
• One from history
http://www.youtube.com/watch?v=Hs22jH61b3E
Chemical BondingIn _________ bonds, two nonmetals share electrons.
covalent
Non-Metals
Examples of Covalent Bonding
H
FH
HF
They aren’t usually very exciting…
