Transcript Basics of Chemistry Powerpoint

“BASICS OF CHEMISTRY”
• ATOMS: Everything in the world is
composed of MATTER. Atoms are the
smallest particle of matter that exist.
What do atoms generally look
like?
• A) NUCLEUS: Contains
protons and neutrons.
• B) RINGS: aka
Orbitals/shells/
• Electron clouds.
Electrons are generally
found in the rings
The most important ring is
the one on the outside.
Called Valence shell.
(Holds Valence electrons)
• The number of
electrons found on the
outer ring allows
atoms to combine with
other atoms.
What does an atom look like?
Fig. 3.1
e- determine the
chemical behavior
of atoms
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Sodium atom
• The number of rings an
element has depends on its
row on the periodic table.
• Because this element has
11 protons, it is sodium.
Sodium is in the third row
(PERIOD) of the P. table,
it has 3 orbital rings.
•
KEY!!!
• There is no limit to the number of Protons
and Neutrons to be found in a nucleus. The
number of electrons allowed on each ring is
different!
• 2 electrons on the first (MAX), 8 electrons
on all of the rest (GENERALLY). This is
known as the OCTET RULE.
PERIODIC TABLE
INFORMATION
• ATOMIC NUMBER: This is the number of
Protons and can also be the number of
electrons if the atom is neutral.
• ATOMIC MASS: This is the number of
Protons and Neutrons.
How do you find the number of
Neutrons?
• Atomic Mass-Atomic
number.
• (AM-AN)
• Number of
• neutrons
• in Sodium?
Ions and Isotopes
IONS
• Number of Electrons are not equal to the
number of Protons.
How is a sodium ion different?
• It is missing an
electron from the last
ring.
• This happens a lot
with elements that are
metals. (Left of the
stairs). The number
they can lose
corresponds to their
column. (Family) on
table.
Types of Ions
• A) Cations: Lose electrons…. causing
their overall charge to now be positive when
comparing protons and electrons.
• B) Anions: Gain electrons…. Causing
them to have an overall negative charge
when comparing protons and electrons.
ISOTOPES
• These differ from neutral atoms because
when COMPARING them to the Neutral
atom, they do not have the same number of
neutrons as the neutral atom has.
• EX: How many neutrons does a carbon
have in its neutral atom? SIX!
• How many neutrons would an isotope of
carbon have?
Carbon Isotopes
• Isotopes of carbon are
now written as
Carbon-13, Carbon14.
• The number 13, 14
refer to the atomic
mass.
Biological importance of Isotopes
• Radioactive Decay: Isotopes that exist in
nature are not stable and so they will
periodically break up into smaller particles.
Biological Importance of
Isotopes continued
• Uses of these particles:
• A) Medicine: Harmless isoptopes that emit
radioactivity can be used as TRACERS for
following or identifying internal problems.
(Thyroid issues.)
• B) Dating fossils: There are some isotopes that
decay at a specific rate. We can use this known
rate (half life) to help determine the age of fossils.
Carbon Dating example:
• If a fossil contains only 12.5% of the carbon that
the organism originally had right before becoming
a fossil, how old is the fossil?
• 100% to 50%= 1 half life (5680 years)
• 50% to 25%= another half life (another 5680
years.)
• 25% to 12.5 %= yet another half life (additional
5680 years)
• Age of fossil: 5680+5680+5680= 17040 years!
Carbon dating…
•
How do you get the atoms to
“stick together”?
•
•
•
•
•
Bonding!
Three types of Bonds:
A) Ionic Bonds
B) Covalent Bonds
C) Hydrogen Bonds
Ionic Bonds
• Form when atoms that were neutral and
then gained or lost electrons from the outer
shell are now attracted to each other
because of charge differences. (Like
opposites attract!)
• KEY: Elements that generally form ionic
bonds contain at least one metal and one
non-metal! Not as strong as Covalent bonds.
Covalent Bonds
• Form when atoms have incomplete outer
shells and have NOT gained/lost electrons,
instead decide to SHARE electrons to reach
the octet rule.
• KEY: Elements that generally form
covalent bonds contain two or more nonmetals. STRONG! Strength increases with
number of shared electrons.
Covalent Bonds
Fig. 3.9 Water molecules contain two covalent bonds
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Hydrogen Bonds
• These are very different from the previous
two bonds. Ionic and covalent bonds
combine atoms into a compound/molecule.
Hydrogen Bonds form between already
formed compounds/molecules thus
making larger molecules. The bonding
occurs between a hydrogen atom and either
an oxygen or nitrogen atom. WEAK!
Hydrogen Bonds
Fig. 3.10 Hydrogen bonding in water molecules
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