The Nature of Matter

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15 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Chapter 2

Chemistry of
Life

Atoms

Atoms

(a) Electrons can be found anywhere in
the cloud

(b) Electrons are represented in orbit
simply to show number

Where are those electrons???

Contrary to popular
belief, electrons
can be found
anywhere in a
cloud at any
moment.

Electrons are NOT
in a predictable
orbit around the
nucleus!!

Element


Substance made of only
one type

of atom


Elements can be naturally occurring or
man
-
made


New elements are discovered every year;
however, they do not last long enough to
be significant

Periodic Table of Elements

C

Chemical
Symbol

Carbon

Chemical
Name

6

Atomic
Number

12.01

Atomic
Mass

Ions


Atom with a positive or negative charge


Positively charged = more protons than
electrons; occurs when atoms lose
electrons (
cation
)


Negatively charged = more electrons than
protons; occurs when atoms gain
electrons (
anion
)

Isotopes


Atoms with different number of neutrons
than typical atoms of the same element


Example:


Carbon typically has 6 protons and 6 neutrons
giving it an atomic mass of 12


An
isotope

of carbon has 6 protons and 7
neutrons giving it an atomic mass of 13


A
radioisotope

of carbon has 6 protons and 8
neutrons giving it a mass of 14

Isotopes of Hydrogen

How Isotopes Are Used


Tracers/Markers


Able to label molecules with isotopes from other
molecules because isotopes have different mass


Using mass spectrometer, can detect where
certain elements go during a chemical reaction


Radiometric (radiocarbon) Dating


Radioactive isotopes (Carbon
-
14) decays at a
steady rate; therefore, they use that to calculate
age of fossils and other artifacts.

Combining Chemical Symbols

Chemical Bonds


Covalent Bond


Ionic Bond


Van der Waals Forces

Types of Covalent Bonds

More Covalent Bonds

Formation of an Ionic Bond

Van der Waals Forces


Weak attraction between atoms and
molecules due to unequal distribution of
electrons


Causes regions of an atom to have
temporary charges (both positive and
negative)


Weakest of chemical bonds

Van der Waals and Geckos

Figure 2
: Structural hierarchy of the gecko adhesive system.

A.

Ventral view of a tokay gecko (
Gekko gecko
).
B
.
Foot of a tokay gecko, showing a mesoscale array of seta
-
bearing scansors (adhesive lamellae).
C
. Array of setae
on the ventral surface of each scansor.
D
. Single gecko seta.
E
. Nanoscale array of hundreds of spatular tips of a
single gecko seta.
F.

Synthetic spatulae fabricated in the lab of Ronald Fearing using nanomolding.

Application of Van der Waals

& the Gecko

http://scienceguy288.wordpress.com/2008/03/26/biomimetics
-
and
-
the
-
future
-
of
-
engineering/

Gecko Tape

http://www.hero.ac.uk/uk/business/archives/2003/sticking_with_gecko_glue5188.cfm

Using nanotechnology to make tape without
chemical adhesives . . . Nanoengineering creates
adhesive 200x more effective than gecko’s feet

Spiderman toy with gecko
tape on the palms . . .
could develop to hold
people as well as toys!!!