Atomic Structure and Chemistry
What is matter?
Matter is anything that
takes takes up space and
has mass.
•
May or may not be visible
(example.... air)
What is an element?
A chemical element is a
pure substance that
consists entirely of one
type of atom.
•
Examples: Gold,
Mercury, Sulfur, &
Hydrogen
•
Over 100 elements
represented on the
Periodic Table of
Elements
Three types of elements
•
Metal - An element with luster (shine), that is a good
conductor of heat and electricity, is malleable (may be
shaped or pounded) and ductile (may be stretched into
wire)
•
Nonmetal - An element that is a gas or brittle solid at
room temperature, and does not conduct heat or
electricity well
•
Metalloid - The element that shares properties of metals
and nonmetals, and may conduct small amounts of
electricity and heat
What is an atom?
An atom is the basic unit
of matter... It is the
smallest particle of an
element that retains the
physical and chemical
characteristics of that
element.
•
Composed of 3 subatomic
particles...
1) Protons
2) Neutrons
3) Electrons
SubAtomic particles
•
Protons - Positively charged
particles found in the nucleus of the
atom that make up about one half
of the mass of an atom
•
Neutrons - Particles without charge
found in the nucleus of the atom
that make up about one half of the
mass of an atom
•
Electrons - Negatively charged
particles orbiting the nucleus of the
atom with 1/1840 the mass of a
proton
More about atoms...
•
Atomic number = # Protons = # Electrons
•
Atomic Mass = # Protons + # Neutrons
Why is that important?
•
# Protons = # Electrons, therefore
individual atom is electrically neutral
•
Like charges repel... Electrons
maintain space between one another.
What about protons?
•
Neutrons act as buffer zones between
positively charged protons
•
Larger number of protons requires
even more neutrons to separate
positively charged particles (so #
Protons does not always equal #
Neutrons)
Energy levels in the electron
cloud
•
Electrons are found orbiting the nucleus in the electron
cloud
•
Different areas where electrons may be found within an
electric cloud are known as energy levels
•
Orbitals in the electron cloud closest to the nucleus have
the lowest energy level... Orbitals farthest from the
nucleus have the highest energy level
•
Orbitals farthest from the nucleus can hold the most
electrons because it allows for the most space between
the electrons
Energy levels in the electron
cloud
Like charges repel
•
Electrons are negatively charged and repel other
electrons. So they orbit in different directions and
regions to stay as far away from each other as
possible...
Election configurations
•
Due to closer proximity to
the nucleus, it is easier to
fill an spherical orbital of
a higher energy level
than an irregularly
shaped orbital with a
lower energy level. So
an s-orbital of the 4th
energy level will fill with
electrons before a dorbital of the 3rd energy
level...
Bohr model of the atom
•
Niels Bohr developed a
model that shows the
energy level position of
electrons around the
nucleus
•
Known as a Bohr Model
Energy levels in the electron
cloud
•
Even though the third level can hold 18 electrons, if 8
electrons are present, the atom will be stable
•
This holds true for the fourth, fifth, sixth, and seventh
levels as well...
•
This idea is represented by an electron dot diagram,
formally known as a Lewis Dot Structure...
Lewis dot structure & the
Bohr model...
Lewis dot structure
•
A Lewis Dot Structure is a
representation of the atom that
only shows valence electrons (the
number of electrons in the outer
orbital), with a maximum number
of eight electrons in the outer shell
•
This electron dot model shows the
tendency of the atom to react with
other atoms due to it's need to
become stable by filling its outer
orbital with eight electrons (known
as the Octet Rule), thus forming a
compound
Lewis dot structure & the
representative elements
What is a compound?
A compound is a substance
formed by the chemical
combination of two or more
elements in definite portions.
•
Examples include water
(H2O ), table salt (NaCl),
and glucose (C6H12O6)
•
The chemical formula
expresses the type of
atoms combined and
number of each type of
atoms...
What is a chemical reaction?
•
When 2 atoms of
Hydrogen join with an
atom of Oxygen, water is
formed...
•
Water forms via a
chemical reaction
•
Chemical reactions occur
by the breaking and/or
forming of bonds
between atoms
Lewis dot structure &
compound formation
Lewis Dot Structures show
the electrons that form
bonds between atoms in
chemical reactions, while
trying to fill their outer
orbitals, forming
compounds via the
reactions
So this electron dot model
shows the way atoms react
with other atoms...
Types of Chemical bonds
•
Ionic bonds - electrons are donated by one atom and accepted
by another
•
Covalent bonds - electrons are shared between atoms
•
Polar Covalent bonds - electrons are shared unevenly between
atoms, resulting in polarity of the molecule
•
Hydrogen bonds - weak attractive force between oppositely
charged atoms
•
Metallic bonds - electrons are shared between many other
metal atoms
Ionic bonds
Electrons are donated by one atom and accepted by the
other... The resulting charged atoms are now called ions.
Formation of Ions
Ions are electrically
charged because the
balance of charge
between protons and
electrons has been upset
by the net loss and gain
of electron(s)
Covalent bonds
Electrons are shared between atoms
Multiple covalent bonds
Multiple electrons are shared between atoms, resulting in
double and triple covalent bonds
Polar covalent bonds
Electrons are shared unevenly between
atoms, resulting in polarity of the molecule
Hydrogen bonds
Weak attractive force between oppositely charged atoms
Hydrogen bonds are
important in biology
•
Water is necessary for life
reactions to occur
•
H-bonding helps proteins
maintain their structure
and therefore, function
•
H-bonding allows DNA
strands to separate and
rejoin easily
Metallic bonds
Electrons are shared between many metal atoms,
as if the atomic nuclei are floating in a sea of
electrons
Mickey molecule...