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The Chemistry of Life The Chemistry of Life (Biochemistry) (Biochemistry)
UNIT 2
Elements, Atoms, and Compounds, OH MY!!!
Elements: the basic chemical units of matter that cannot be broken down by typical chemical processes
Atoms: The smallest unit of an element
Compound: Any combination of two or more elements in fixed ratio
Different arrangements of atoms determine a compounds properties
Elements, Atoms, and Compounds, OH MY!!!
There are 92 naturally occurring elements 25 are required by living organisms
Only 4 elements make up 96% of our body
Atomic Structure Nucleus: The core/center of
the atom, made of Protons and Neutrons Protons = Positive Charge Neutrons = Neutral
Charge Electrons have a negative
charge, and surround the nucleus
Elemental Differences/The Periodic Table
Atomic Number: The number of protons that all atoms of this element have This is also usually the
number of electrons, which makes the atom neutral (equal + and -)
The # of protons give the element its unique properties
Atomic Mass: Protons + Neutrons
Electrons Atoms have electron shells that can hold different
numbers of electrons Level 1: Holds 2 max Levels 2 and 3: Each holds 8 max
Valence Shell: The outermost shell of an atom The electrons on that shell are called
valence electrons ATOMS WANT FULL VALENCE SHELLS!!!
How many more electrons can this atom’s valence shell take?
2
2
2
Protons
Neutrons
Electrons
Helium atom
Massnumber = 4
6
6
6
Protons
Neutrons
Electrons
Carbon atom
Massnumber = 12
Electroncloud
Nucleus
2e–
6e–
Other Atom Types Ion: When an atom has more or less electrons
than protons This makes it more reactive
Two Kinds: Cation = Positive, and has one less electron Anion = Negative, and has one extra electron
Isotopes: An atom that has the same number of protons, but different number of neutrons than normal
Ways of Drawing Atoms
Bohr Model: Actually shows all electron rings and electrons “Looks like an atom”
Lewis Dot: Just shows the atomic symbol and the valence electrons Useful because
valence electons control bonding
Bellringer
“WORD IS BOND” Give me your definition of the word bond What/who are the things/people you are
bonded to in your life? Do opposite’s attract in your opinion? What is an ion?
Agenda Objective: To discuss chemical bonding Agenda:
Bellringer/Discussion Notes Grade Lewis Dot WS Start Atomic WS
Homework: Atomic WS due tomorrow
Bellringer Tell me the
following: # of Protons # of Electrons # of Neutrons # of Valence
electrons
Bonding Atoms have electron shells that can hold different
numbers of electrons Level 1: Holds 2 max Levels 2 and 3: Each holds 8 max
Valence Shell: The outermost shell of an atom The electrons on that shell are called valence
electrons ATOMS WANT FULL VALENCE SHELLS!!!
How many more electrons can this atom’s valence shell take?
Bonding An atoms ability to bond is controlled by its
number of valence electrons Chemical Bonding: When atoms without a
full valence shell share or transfer electrons with other atoms to fill their valence shell
Two Types: Ionic Bonds Covalent Bonds
Ionic Bonds Review: What is a cation? An anion? Ionic Bonds: When two ions of opposite
charge of (an anion and cation) bond together
1. One atom gives up or takes an electron from another, making them both ions!!!
2. Then they stick together3. Why?: Opposite attract! Example: Sodium Chloride (NaCl, Table
salt)
Na
Sodium ionCl
Chloride ion
Sodium chloride (NaCl)
Covalent Bonds Covalent Bonds: When two atoms are
bonded because they “share” electrons to fill their valence shells!
Molecule: When two atoms are bonded covalently
If two electrons are shared, then it is a double bond, if three, it is a triple bond
Bellringer Tell me everything you can about these elements
Agenda Objective: To continue working with the bonding
models Agenda:
Bellringer/Discussion Bonding Model
Homework: Model Write-Up due tomorrow Bonding Worksheet
Molecule Models
Make Models of the following Molecules: H2, O2, H2O, CO2, CH4, C2O2, C2OH2, C6H12O6
On your sheet, you must draw the following: Lewis Dot Structures of each atom pre-bonding Line/Lewis Dot Structures post-bonding Label single/double bonds COPY THIS EXAMPLE DOWN!!!
Bellringer What does “Polar”
mean? Do you like
water? Why/why not?
Agenda Objective: To discuss water’s polarity and
characteristics Agenda:
Bellringer/Discussion Notes Grade Bonding WS
Homework: Lab Tomorrow!
Polar Molecules Polar Molecules: When a covalently bonded
molecule unequally shares its electrons and has a “negative” and “positive” end
One part of the molecule is positive, and one is negative
Hydrogen Bonds Hydrogen Bonds: When
polar molecules get weakly bonded together between their slight positive and negative ends
These occur in many Biologically important compounds Water, DNA, Proteins
Hydrogen bond
Water!!! Water is a polar
molecule that easily forms hydrogen bonds.
Because of this, it has four characteristics that has allowed life exist on Earth