Download Chapter 2 - Saint Joseph High School

9/22/14
Chapter 2: The Chemistry of Life
Chapter 2: The Chemistry of Life
2–1
The Nature of Matter
Mr. M. Varco
St. Joseph High School
2.1: Atoms
•  What are human made of?
–  All materials are made of matter (solid, liquid, gas)
•  The study of chemistry begins with the basic unit of matter, the atom,
which is the smallest particle.
•  Atoms are composed of three sub-atomic particles
–  Protons (+)
–  Neutrons ( )
–  Electrons (-)
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2.1: Atoms
•  Strong forces bind protons and neutrons to form the Nucleus at the
center of the atom
•  Electrons are in constant motion around nucleus, and are attracted to
the positively charged nucleus
•  Despite their charges, atoms themselves are electrically neutral
because atoms have equal number of protons and electrons
2.1: Elements and Isotypes
•  An element is a pure substance that consists entirely of one type of
atom.
–  More than 100 elements are known
–  Carbon (C), Hydrogen (H), etc.
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C
Atomic
Number
Carbon
12.011
•  Atomic Number: the number of protons in the nucleus of an element
•  Example: Carbon (C) à Atomic number =
à Protons = ?
à Electrons = ?
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2.1: Elements and Isotypes
Atomic
Number
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C
Carbon
12.011
2.1: Elements and Isotypes
Recall:
Atomic # = Proton #
Proton # = Electron #
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2.1: Elements and Isotypes
•  All atoms of an element have the same number of protons. However,
the number of neutrons of an element’s atoms can vary.
•  Ex: All atoms of carbon have 6 protons and 6 electrons
–  Some carbon atoms have 6 neutrons, while other have more.
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C
Carbon
12.011
2.1: Elements and Isotypes
•  Isotope: Atoms of the same element that differ in the number of
neutrons they contain
–  Isotopes are identified by their mass number
•  Mass Number: Total number of protons and neutrons in the nucleus
of an atom
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C
Carbon
12.011
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2.1: Elements and Isotypes
•  Isotope: Atoms of the same element that differ in the number of
neutrons they contain
–  Isotopes are identified by their mass number
•  Mass Number: Total number of protons and neutrons in the nucleus
of an atom
Isotope
# of Protons
# of Neutrons
# of Electrons
Carbon-12
(nonradioactive)
6
6
6
Carbon-13
(nonradioactive)
6
7
6
Carbon-14
(radioactive)
6
8
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2.1: Chemical Compounds
•  Compound: a substance formed by the chemical combination of two
or more elements.
–  Compounds are written in chemical formula: Na + Cl = NaCl
•  The physical and chemical properties of a compound are usually
different from those of the elements from which it was formed
H2
Gas
+
O
Gas
=
H 2O
Water
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2.1: Chemical Bonds
•  Atoms in a chemical compound are held together by Chemical Bonds
•  Two main types of chemical bonds in chemistry are:
–  Ionic Bonds
–  Covalent Bonds
2.1: Chemical Bonds
•  Ionic Bonds are formed when one or more electrons are transferred
from one atom to another
•  A loss or gain of electrons results in a positively or negatively charged
atom known as an Ion
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2.1: Chemical Bonds
Ionic Bonding
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Protons +17
Electrons -17
Charge
0
2.1: Chemical Bonds
•  Electrons may be transferred to another atom (Ionic Bonding) or
shared between atoms
•  Covalent Bond: Sharing of electrons between the nuclei of two atoms
–  Single Covalent Bond (sharing of two electrons)
•  Molecule: the smallest unit of most compounds, which result when
atoms are joined together by covalent bonds.
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