2-1 The Nature of Matter
The Chemistry of Life,
The Nature of Matter 2-1
2-1 The Nature of Matter
Hierarchy of Science
A hierarchy is a system
of organizing and ranking
things.
2-1 The Nature of Matter
Hierarchy of Science
A hierarchy is a system
of organizing and ranking
things.
It comes from the Greek,
meaning ‘sacred rule’
2-1 The Nature of Matter
Math provides tools for
measuring basic quantities.
Mathematics
2-1 The Nature of Matter
Math provides tools for
measuring basic quantities.
Physics studies basic things,
like matter, motion and
energy.
PHYSICS
Mathematics
2-1 The Nature of Matter
Math provides tools for
measuring basic quantities.
Physics studies basic things,
like matter, motion and
energy.
CHEMISTRY
Chemistry studies the
ways that matter and
energy are arranged.
PHYSICS
Mathematics
2-1 The Nature of Matter
“other
stuff”
BIOLOGY
CHEMISTRY
BIOLOGY
studies a
particular kind
of arrangement
of matter and
energy: LIFE !
PHYSICS
Mathematics
2-1 The Nature of Matter
Atoms:
• appear as elements in the Periodic Table
• have a dense nucleus at their center
• consist mostly of……empty space !
2-1 The Nature of Matter
Subatomic Particles
Particle
Symbol A.M.U.* Charge Location
------------------------------------------------------proton
neutron
electron
p+
n
e-
1
1
0*
positive
neutral
negative
nucleus
nucleus
cloud
Actually, an electron has a mass, but it’s very
small: 1,867 times smaller than the proton
or the neutron
2-1 The Nature of Matter
nucleus of an atom of carbon:
12
2-1 The Nature of Matter
The protons and the neutrons
are found in the nucleus:
Nuclear particles,
or nucleons
2-1 The Nature of Matter
The electrons, meanwhile, are
in motion outside the nucleus !
2-1 The Nature of Matter
Electrons:
• occupy energy levels sometimes called
shells or orbitals
• with the greatest energy are those whose
shells are farthest from the nucleus
2-1 The Nature of Matter
Orbitals:
• are the place where the electron (e-) of a
given atom is most likely to be found !
• which are outermost (s and p orbitals)
determine an atom’s properties
2-1 The Nature of Matter
The Periodic Table:
2-1 The Nature of Matter
The Periodic Table:
• was first proposed by Mendeleev (1871)
• is a system for classifying the elements,
based on common properties
• columns are groups or families
• rows are periods: one electron (e-) is
added every time you move to the right
2-1 The Nature of Matter
Using the Periodic Table
The Symbol (shown as ‘X’) gives the name of
the element
– first letter capitalized
– second letter, if required, lower case
2-1 The Nature of Matter
Atomic Number
:
(‘the A number’)
• identifies the element
• is equal to the number of protons (whole
number) in any given atom of that element
2-1 The Nature of Matter
Atomic Number
:
(‘the A number’)
• also equals the number of electrons if the
atom is neutral !
2-1 The Nature of Matter
Atomic Mass
(‘the Z number’):
• the weighted average of the masses of the
isotopes of that element
• usually expressed as a decimal, rather than
as a whole number
2-1 The Nature of Matter
A quick way to show this
information for a single atom:
2-1 The Nature of Matter
Isotopes:
• are atoms of the same element, but with
different masses
• differ in the number of neutrons, but the
number of protons remains the same !
EXAMPLES:
12C
: 6 protons . . . . . . . . . . .6 neutrons
13C : 6 protons . . . . . . . . . . .7 neutrons
14C : 6 protons . . . . . . . . . . .8 neutrons
2-1 The Nature of Matter
Ions:
• are atoms of the same element, but which
differ in charge
• differ in the number of electrons, but the
number of protons remains the same !
EXAMPLES:
Na (neutral) 11 protons . . . . . . .11 electrons
Na+ (ion) 11 protons. . . . . . . . . .10 electrons
Cl- (ion) : 17 protons . . . . . . . . .18 electrons
2-1 The Nature of Matter
Ionic Bonds:
• electrons are
transferred
• ions (atoms or
molecules with an
overall net charge)
are formed
2-1 The Nature of Matter
Covalent Bonds:
• electrons are shared, travelling
around both nuclei: (wow !)
• stable molecules of larger sizes
(macromolecules) become possible
2-1 The Nature of Matter
Covalent Bonds:
• Single bonds– share
just 1 pair of e• Double bonds– share
2 pair of e• Triple bonds – share
3 pair of e-
2-1 The Nature of Matter
Polar Covalent Bonds:
• electrons are shared unequally
• opposite ends of molecule carry small
opposite charges (+ and -)
• Examples include water (H20), shown below: