The Chemistry of Life (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 Mass number = Protons Neutrons Electrons Carbon atom Mass number = 12 Electron cloud 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 together 3. Why?: Opposite attract! Example: Sodium Chloride (NaCl, Table salt)

Na  Sodium ion Cl  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: H 2, O 2, H 2 O, CO 2, CH 4, C 2 O 2, C 2 OH 2, C 6 H 12 O 6 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