Download 1. Atoms and Bonding

Chemistry of Life
What’s the Matter?
All of the materials around you are made up of
matter. You are made up of matter, as are the
chair you sit on and the air you breathe.
1. Give an example of solid matter.
2. Give an example of liquid matter.
3. Give an example of gaseous matter.
4. Is all matter visible?
5. Does all matter take up space?
Matter & Mass
Matter: Anything that has mass and takes
up space
Mass: Measure of the amount of matter an
object contains
The Nature of Matter
Atoms
Smallest part of an element
From Greek work atomos = Unable to be cut
or indivisible
Made up of 3 parts
 Protons (+) charge  nucleus
 Electrons (-) charge  electron cloud
 Neutron (no charge)  nucleus
Element
Pure substance, contains only 1 type of atom
More than 100, but only about 2 dozen are found
in living things.
4 elements that make up 96% of living matter
H (hydrogen), O (Oxygen), N (Nitrogen), C (Carbon)
6 most common - CHNOPS
Atomic #
Atomic Symbol
Element Name
Atomic Mass
Atomic Number
Number of protons and or electrons
Atomic # = p+ = eAtomic Mass or Mass Number
Number of protons + number of neutrons
p+ + n = mass number
n= mass number – p+
Practice
1. What is the atomic # of Carbon?
2. How many electrons does Boron have?
3. What is the mass number of Neon?
4. How many protons does Helium have?
5. How many neutrons does Chlorine
have?
Isotopes
An element with the same number of
protons but different number of neutrons
Isotopes
Isotopes of Carbon
Nonradioactive carbon-12
6 electrons
6 protons
6 neutrons
Nonradioactive carbon-13
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
Radioactive Isotopes
 Unstable nucleus
 Break down at a constant rate
 Used to date rocks & fossils
 Used as a cancer treatment
 Used to kill bacteria
 Used as “tracers” follow movement of
substances in an organism
PET (positron emission tomography) SCANS
http://www.youtube.com/watch?v=GHLBcCv4rqk
Other scans using radioactive
tracers
A hepatobiliary (HIDA) scan is an imaging
procedure used to diagnose problems in
the liver, gallbladder and bile ducts.
http://www.youtube.com/watch?v=VDihrC
1RnYE
Chemical Compounds
Compound
Chemical combination of 2 or more different
elements
Composition of compound is shown by molecular
formula
Ex] H2O
Physical & chemical properties of a compound are
very different than those of the elements that
make it up
EX] NaCl
Chemical Bonds
 Atoms in compounds are held together by
chemical bonds
 Bonds involve electrons in outer energy
level
 Outer most energy level is known as the
valence shell
1st  2 electrons
2nd  8 electrons
3rd  18 electrons
 Valence shell holds a maximum of 8
electrons
1) Covalent Bonds
Elements share electrons for stability.
Number of bonds? Use “HONC-1234”
Quite strong… takes a lot of energy to
break them!
– But you CAN, because we burn fat, recycle
materials… plants break bonds in CO2 and
H20 to rework them into complex sugars
Ex: H2O, CO2, C6H12O6 (glucose)
– Some polar, some non polar…. 
Covalent Bond
Molecular structures of
covalent compounds
Glucose
Hemoglobin
DNA
(polar covalent?)
Oxygen is more greedy for electrons
than hydrogen, so it has more ‘custody’
Creates partially negative and positive
areas
2) Ionic Bonds
involve the transfer of electrons.
Whether they donate or receive is
determined by the number of electrons
in the valence shell.
– Cation: positive (b/c it lost e-)
– Anion: negative (b/c it stole e-)
– Due to extreme differences in
electronegativity
Ex: NaCl (table salt) or KI (a stain) or
CaCO3 (in seashells)
Figure 2-3 Ionic Bonding
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Protons +17
Electrons -17
Charge
0
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Like & Unlike charges
3) Hydrogen bonds
Usually between water molecules
(makes them cohesive)
Causes:
– Ice’s low density
– Sweat’s cooling power
– Plants drinking ‘against gravity’
– Insects to walk on water
3) Hydrogen bonds
Ice
Sweat
Cohesion
Relative
Bond
Strengths
Chemistry Summary
Everything around you is made of matter
composed of atoms
Atoms - nucleus of protons and neutrons
surrounded by a cloud of electrons.
Elements have different # p+ , e-, and n0
Isotopes have the same # p+ but diff # n0
Chemistry Summary
Compounds have 2 or more elements
Bonds form from interaction of outer eCovalent bonds- strongest - share eIonic bonds – medium – trade e– Water soluble
Hydrogen bonds – weak – interaction b/w
polar molecules