Transcript Atoms and Molecules

The Basic
Structure and
Function of
Atoms,
Molecules
and
Chemical Bonds:
Covalent,
Ionic,
and
Hydrogen
Atoms Are the Units of Structure
and Function of Matter
• Atoms are composed of :
– Protons – have mass, are
positively charged, reside
in the nucleus and give the
specific characteristics to
an atom.
– Neutrons – have mass are
neutral and reside in the
nucleus.
– Electrons – have very little
mass, are negatively
charged and reside in
energy levels that orbit the
nucleus.
Atomic Statistics
•
Chemical symbols for an element shows its mass
(weight) number at the top and its atomic number at the
bottom. This is the symbol for carbon. A neutral Carbon
atoms has six protons, six electrons, and 12 - 6 = 6
neutrons.
• Atomic Number – the # of protons in an atom’s nucleus, this
determines the “kind” of atom. In neutral atoms, the # of
protons is equal to the # of electrons. Elements are composed
of only one kind of atom.
• Ions – Atoms that have different # of protons versus electrons,
therefore they are “charged”.
• Atomic Mass – the # of protons plus the number of neutrons in
an atom’s nucleus. Aka atomic weight.
• Isotopes – atoms that have the same # of protons but vary in
the number of neutrons.
Atoms: Components of Elements
• Atoms of the same kind have the same number of
protons.
• Elements are substances that cannot be broken down
by ordinary chemical means. They are composed of
only one kind of atom.
• Click on the link below for the Periodic Table of
Elements
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Elements Essential to Life
• Carbon, Hydrogen,
Oxygen, and Nitrogen
are the four elements
that make up most of
the matter in living
things.
• In the body of
organisms, most other
essential elements are
found only in trace
amounts.
Carbon Is the Structural Backbone
of Organic Molecules
• Organic chemistry
pertains to Carbon
based molecules found
in living things.
• Carbon can chemically
bond to four other
atoms and serves as a
“structural” backbone
for organic molecules.
Electron Arrangement in an Atom’s Outermost Energy
Level Determines Chemical Bonding Properties
• In an atom, electrons reside at certain energy levels, which
are at specific distances away from the nucleus, known as
shells.
• The first shell, closest to the nucleus, may “fit” up to two
electrons, a duet.
• Outer shells, may fit up to eight electrons, an octet.
• Atoms, whose outermost energy levels are not full, participate
in chemical bonding with other atoms.
Ionic Bonding
• Ionic bonding occurs when one atom gives its
electron to another.
– Ions, are formed as the atom that gains the electron
becomes negatively charged and the atom that loses
the electron becomes positively charged.
– Ionic bonds form due to the attraction between ions
of opposite charge.
Covalent Bonds
• Covalent bonds occur
when atoms share one
or more pairs of outer
shell electrons with
each other to fulfill their
duet and/or octet.
– Single bond – one pair
of electrons is shared.
– Double bond - two
pairs of electrons are
shared.
– Triple bond – three pairs
of electrons are shared.
Polar Covalent Bonds
When electrons are
not equally shared
between two atoms,
that are chemically
combined in a covalent
bond, one atom will
pick up an overall
negative charge and
the other atom will pick
up an overall positive
charge. This produces
polar compounds,
such as water, H2O.
Hydrogen Bonds
• Hydrogen bonds are
weak electrostatic
bonds that are formed
when Hydrogen is a
part of a polar
covalent bond, where
its partial positive
charge will allow it to
share attraction with
other electronegative
atoms, such as
Oxygen.
• Ex. Water H2O
The Hierarchy of Molecular Complexity Leads to
Chemical Structures that Have Specific Functions
Ionic
Bonds
Covalent
Bonds
Hydrogen Bonds
Salts
Hydro-carbons
Water