1 CLIFFS NOTES CHEMISTRY Chapter 2: The Cliff Notes to Chemistry • What is Chemistry? • Atoms • Subatomic Particles • Chemical Bonds •H 2 O Chapter 2: The Cliff Notes to Chemistry CLIFFS NOTES CHEMISTRY •Every object around you is made up of mass . •Mass is made up of matter . •Matter is made up of little particles called atoms . • Chemistry is the science that deals with matter • Matter is anything that takes up space and has mass – Living or non-living • Smallest stable units of mass are atoms CLIFFS NOTES CHEMISTRY Why is Chemistry Important to Biology? CARBON ATOM All living things are made of atoms CARBON ATOM Another Example DNA A Cell Cells Nucleus within cell Kidney Tissue An organ: Frog Kidney An organism: A frog All living things are made of atoms DNA A Cell DNA is a large molecule, comprised of atoms!! nucleus CARBON ATOM Zoom in on DNA
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CLIFFS NOTES
CHEMISTRY
Chapter 2: The Cliff Notes to
Chemistry
• What is Chemistry?
• Atoms
• Subatomic Particles
• Chemical Bonds
• H2O
Chapter 2: The Cliff Notes to
ChemistryCLIFFS NOTES
CHEMISTRY
•Every object around you is made up of mass.
•Mass is made up of matter.
•Matter is made up of little particles called atoms.
• Chemistry is the science that deals with matter
• Matter is anything that takes up space and has
mass
– Living or non-living
• Smallest stable units of mass are atomsCLIFFS NOTES
CHEMISTRY
Why is Chemistry Important to
Biology?
CARBON ATOM
All living things are made of atoms
CARBON ATOM
Another Example
DNA
A Cell
Cells
Nucleus within cell
Kidney Tissue
An organ: Frog Kidney
An organism: A frog
All living things are made of
atoms
DNA
A Cell
DNA is a large molecule, comprised of atoms!!
nucleus
CARBON
ATOM
Zoom in
on DNA
2
• Atoms are composed of subatomic particles
The Structure of Atoms
– A proton is positively charged
– A neutron is electrically neutral
– An electron is negatively charged ]
Packed
In the atomic
nucleus
Orbits the
nucleus
How many protons, neutrons and electrons does a carbon atom have?
CARBON ATOM
The Structure of Atoms
How many protons, neutrons and
electrons does a helium atom have?
HELIUM ATOM
http://www.purchon.com/chemistry/helium.htm
The Structure of Atoms
• OK, atoms are obviously very, very, small and theyprobably don’t ‘weigh’ very much, or have much mass
• But, believe it or not, atoms do have mass
• Atomic mass is determined by the # of protons andneutrons.
• What is the atomic mass of a carbon atom? A heliumatom?
• Electrons do not contribute (much) to the mass (weight)of an atom.
Atoms
• Atomic mass (# of protons plus the # of
neutrons)
• Atomic number (# of protons)
• What about the electrons?++
++
What do you think makes a carbon
atom a carbon atom, and not a helium
atom?
HELIUM ATOM CARBON ATOM
Who am I?
What makes me
me?
What is the
meaning of life?
I think,
therefore I
am…a
carbon atom
Elements– Atoms are classified into groups called
elements
– Elements are substances that cannot be
broken down into other substances
– There are 92 naturally occurring elements on
Earth
– You can find all of them on the periodic table
HeliumLead
3
groups
periods
Periodic Table
(of course you do not have to memorize this!)
(C) Carbongroups
periods
Periodic Table
(of course you do not have to memorize this!)
Just focus
on these
four
elements
Why these four elements?
– 25 elements are
essential for life
– Four of these
make up about
96% of the
weight of the
human body
– Trace elements
occur in smaller
amounts
1.
2.3.
4.
The Periodic Table contains lots of
useful information
What does this tell us?
What does this tell us?
Why do we care?
• In an atom of carbon, if the atomic numberis 6, how many protons are there?
• How many electrons are there??
• It’s the electrons that we really care about!
+++
+
Electrons Orbit the Atomic Nucleus
• If protons were the size of a
tennis ball, electrons would
be orbiting the nucleus at a
distance of 6 miles away!!
• Outer most electrons (or
the lack-thereof) determine
how one atom interacts with
another atom
•Atoms may interact and form bonds, generating
larger, more complex molecules (like DNA)
4
DNA is a molecule
Molecules are made of atomsElectron Arrangement
• Electrons (e-) are arranged around the
atomic nucleus in electron shells (orbitals).
• Electron shells closest to the nucleus have
the lowest energy, while electrons farther
from the nucleus have greater energy.
• The first electron shell holds only 2 electrons
• The next electron shell holds up to 8 electrons
• The four elements most abundant in living things
only have these two shells (phew!)
Electron Shells
In case you forgot those four elements,
they are:
HYDROGEN (only has the first shell)
CARBON
NITROGEN
OXYGEN
Electron Arrangement in a Carbon Atom
Firstelectron shell(can hold2 electrons)
Outermostelectron shell(can hold8 electrons)
Carbon (C)Atomic number = 6
Electron Arrangement in a Carbon Atom
Firstelectron shell(can hold2 electrons)
Outermostelectron shell(can hold8 electrons)
Carbon (C)Atomic number = 6
Rules to figuring out electron
arrangement:
1. What is the atomic number?
2. The number of total electrons is
the SAME as the atomic number.
- For carbon, it is 6
3. Place two electrons in the ‘first’
inner shell
4. Place remaining electrons in the
outer shell.
***To understand how an atom will
interact with other atoms, look at
how many ‘open atom spots’
there are left in the outer shell!
What is the arrangement of outer
shell electrons in an oxygen atom?8
O16
5
Atoms of the four elements most
abundant in life
Electron
Firstelectron shell(can hold2 electrons)
Outermostelectron shell(can hold8 electrons)
Carbon (C)Atomic number = 6
Nitrogen (N)Atomic number = 7
Oxygen (O)Atomic number = 8
Hydrogen (H)Atomic number = 1
Outer shell
electrons?
Outer shell
electrons?Outer shell
electrons?
Outer shell
electrons?
Atoms ‘prefer’ to have their outer
shell FILLED with electrons!
Oxygen (O)Atomic number = 8
Hydrogen (H)Atomic number = 1
I, HYDROGEN,
would strongly
prefer to have 2
electrons in my
outer shell, and
not just 1!
I, OXYGEN,
would strongly
prefer to have 8
electrons in my
outer shell, and
not just 6!
• The first electron shell holds only 2 electrons
• The next electron shell holds up to 8 electrons
• Atoms (with the exception of Hydrogen and
Helium) prefer to have 8 electrons in the outer
electron shell
• The octet rule.
Atoms can ‘fill’ their outer electron shells
by forming chemical bonds with other
atoms
• Atoms can steal electrons from other
atoms; atoms can lose electrons to other
atoms
– Ionic bonds
• Atoms can share electrons with another
atom or atoms
– Covalent bonds
Next up….Chemical Bonds
Oxygen (O)Atomic number = 8Hydrogen (H)
Atomic number = 1
…..OR, what
will happen
when an atom
of OXYGEN
‘sees’ an atom
of
‘HYDROGEN’?
..Two atoms of
HYDROGEN??
Elements with unfilled electron
shells are reactive
• Chemical bonds are formed
• Three types of chemical bonds
1. Ionic bonds
2. Covalent bonds
3. Hydrogen bonds
Oxygen (O)Atomic number = 8
Hydrogen (H)Atomic number = 1
Hey there
hydrogen,
you wanna
bond??
6
Ionic bonds are formed between
ions
• Remember that the atoms we have
discussed so far are electrically neutral
• Because the number of protons (+) was
equal to the number of electrons (e-)
• An ion is a charged species
– Anions
– Cations
Anions and Cations
• If an atoms gains an electron (e-), what happens
to its electrical charge?
• If an atom loses an electron (e-) what happens
to its electrical charge?
Formation of a sodium ion, Na+
Ionic bonds are formed between
ions
Sodium metal Chlorine GasTable salt (NaCl)
+
Ionic Bonding
Reactant(s) Product(s)
In a CHEMICAL REACTION there are reactants and
products. Note that during chemical reactions no atoms