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Community Ecosystem Population BIOSPHERE Organelles Subatomic particles

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4 STATES OF MATTER Solid LiquidGas Definite shape Shape of containerNo definite shape Definite volume Volume of containerNo def. volume Tightly packed May overlapVery spread out Vibrate in place Move fasterVery fast

A chemical element is a substance that cannot be broken down to other substances by ordinary chemical means About 25 different chemical elements are essential to life Life requires about 25 chemical elements but four are most important

Goiters are caused by iodine deficiency Figure 2.2

Atoms smallest unit of an element How are the protons, neutrons, and electrons determined? How is the shorthand version written?

9 DIATOMIC ELEMENTS Elements that must exist naturally as 2 atoms bonded together (until it forms a chemical bond with any other element) Br I N Cl H O F H 2 N 2 O 2 F 2 Cl 2 Br 2 I 2

Atom vs. Element atoms are the individual units of an element An example is hydrogen. Hydrogen exists as 2 atoms of the element bonded together.

Atoms of each element are distinguished by a specific number of protons Table 2.4 – The number of neutrons may vary – Variant forms of an element are called isotopes – Some isotopes are radioactive Isotopes Isotope of???

Radioactive isotopes can be useful tracers for studying biological processes PET scanners use radioactive isotopes to create anatomical images Connection: Radioactive isotopes can help or harm us Figure 2.5BFigure 2.5A

Atomic Structure

ELECTRON ENERGY LEVELS Atomic structure demonstrates the 2, 8, 8 rule. The farther the electron is from the nucleus, the greater the potential energy (energy due to its location….farther from the opposing positive protons).

Noble Gases “Inert”

Electrons are arranged in shells – The outermost shell determines the chemical properties of an atom. Unpaired electrons are involved in bonding. Electron arrangement determines the chemical properties of an atom HYDROGEN (H) Atomic number = 1 CARBON (C) Atomic number = 6 NITROGEN (N) Atomic number = 7 OXYGEN (O) Atomic number = 8 Electron Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons)

17 CHEMICAL BONDING

Elements forming Compounds 18 + = Sodium is a silver-colored metal that reacts so violently with water that flames are produced when sodium gets wet. Chlorine is a greenish- colored gas that is so poisonous that it was used as a weapon in World War I. When chemically bonded together, these two dangerous substances form sodium chloride, a compound so safe that we eat it every day - common table salt!

Compound vs. Molecule A compound is a result of 2 or more different elements combined in a fixed ratio. Water is a compound formed when 2 hydrogen bond with one oxygen. Imagine a waterfall……explain compound vs molecule with this example.

When atoms gain or lose electrons, charged atoms called ions are created – An electrical attraction between ions with opposite charges results in an ionic bond Ionic bonds are attractions between ions of opposite charge Figure 2.7A Na Sodium atom Cl Chlorine atom Na + Sodium ion Cl – Chloride ion Sodium chloride (NaCl) NaClNaCl + –

21 Bohr Model Method: Step 1: Draw the energy levels for each element Step 2: Show the arrow of transfer. There should be an arrow showing transfer for EACH electron given away. (Just like the top picture) Step 3: State the ions below each atomic structure to indicate that electrons have been gained or lost. IONIC BOND: Bohr Method

22 IONIC BOND: Lewis Dot Structure NaCl MgO Lewis Dot Method: Step 1: Write the symbol for each atom separately and show valence electrons (evenly spread out ) Step 2: No arrows. Write ions once transfer has taken place. Show electrons for the ORIGINAL outer shell (the one that gained will show electrons). Remember that ions are written as symbol with superscript.

REDOX REACTIONS Reduction = gain electrons Oxidation = lose electrons

24 COVALENT BOND: Bohr Model Bohr Model Method: Step 1: Draw the energy levels for each element separately. Step 2: Show the energy levels joined (similar to the top picture) All diatomic elements Demonstrate a Covalent bond Remember: BrINClHOF (Chlorine is shown to the right)

25 Molecular formula COVALENT BOND: Lewis Dot Structure Lewis Dot: Step 1: Draw the dot diagram for each element individually (use X and for different atoms) Step 2: Draw the dot diagram for the compound Step 3: Show the molecular formula (including lone electrons)

Electronegativity Chart In a covalent compound, the more electronegative an atom, the greater the pull on the electrons that are being shared. Therefore, it is an unequal tug of war. Nonpolar covalent = equal sharing Polar covalent = unequal sharing

Polar covalent bonds in a water molecule This results in a partial negative charge on the oxygen and a partial positive charge on the hydrogens. H2OH2O –– O H H ++ ++ Because oxygen (O) is more electronegative than hydrogen (H), shared electrons are pulled more toward oxygen.

A hydrogen bond Water (H 2 O) Ammonia (NH 3 ) –– ++ O H H ++ –– N H H H A hydrogen bond results from the attraction between the partial positive charge on the hydrogen atom of water and the partial negative charge on the nitrogen atom of ammonia. ++ ++ ++

Van der Waals Weak, temporary attraction Due to the constant motion of electrons in the orbitals, all atoms may be attracted to one another just because they are close and exhibit a positive or negative region at the right moment. Look at Neon to the right…..Neon is a noble gas and will never bond.

In a chemical reaction: –reactants interact –atoms rearrange –products result Chemical reactions rearrange matter REARRANGEMENTS OF ATOMS 2 H22 H2 +O2O2 → 2 H 2 O Figure 2.17A

31 CHANGES IN STATE Latent Heat = energy absorbed (stored) or released Heat of fusion = energy released; Gas to Liquid to Solid Heat of Vaporization = energy absorbed; Solid to Liquid to Gas

Hydrogen bonds between water molecules Hydrogen bonds  + + ++ H H ++ ++ –– –– –– –– The polarity of water is crucial to understanding its unique properties. Explain how electronegativity plays a role in the attraction of water molecules.

Why water allows for life to exist on Earth….. –Cohesion and Adhesion increase surface tension –Ice is less dense than liquid water –Moderates temperature –Universal Solvent

Water transport in plants Water conducting cells 100 µ m Hydrogen bonds between neighboring water molecules hold the substance together, resulting in a cohesive property of water. Adhesion, the “sticking” of one substance to another, also contributes to the transport of water from roots to shoots. The collective strength of water’s hydrogen bonds results in surface tension.

Due to hydrogen bonding, water molecules can move from a plant’s roots to its leaves Insects can walk on water due to surface tension created by cohesive water molecules Hydrogen bonds make liquid water cohesive

Molecules in ice are farther apart than those in liquid water Ice is less dense than liquid water Hydrogen bond ICE Hydrogen bonds are stable LIQUID WATER Hydrogen bonds constantly break and re-form

Ice: crystalline structure and floating barrier Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Hydrogen bond Floating ice protects the Liquid water below from the Colder air. If ice sank, it would seldom have a chance to thaw Ponds, lakes, and oceans would eventually freeze solid

Water can absorb high amounts of energy with little change in its temperature….SPECIFIC HEAT Temperature Moderation

Specific Heat of Water compared to………. Imagine the beach……..

An importance of Water in terms of air temp…. Now imagine if our planet did not have water…… Imagine a desert-like condition……

Solutes whose charges or polarity allow them to stick to water molecules dissolve in water –They form aqueous solutions –Solutes may dissolve in a solvent until saturation is reached Water is a versatile solvent Ions in solution Salt crystal Cl – Na + Cl – – –– – – Na

A crystal of table salt dissolving in water Negative Oxygen regions of polar water molecules are attracted to sodium cations (Na + ) Cl – – – – – Na + Positive hydrogen regions of water molecules cling to chloride anions (Cl – ) – – – – – – Na + Cl –

Acids and Bases Substances that breakdown to produce more hydrogen ions than hydroxide ions are…… Substances that breakdown to produce more hydroxide ions than hydrogen ions are…… Substances that breakdown to produce equal amounts of hydrogen ions than hydroxide ions are……

pH = “potential Hydrogen” Aqueous solutions have the total concentration of H + ions and OH - is a constant…

Cells are kept close to pH 7 by buffers Buffers are substances that resist pH change – They accept H + ions when they are in excess and donate H + ions when they are depleted – Buffers are not foolproof

Some ecosystems are threatened by acid precipitation Acid precipitation is formed when air pollutants from burning fossil fuels combine with water vapor in the air to form sulfuric and nitric acids Connection: Acid precipitation threatens the environment

Figure 3.9 Acid precipitation and its effects on a forest More acidic Acid rain Normal rain More basic