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