Basic Chemistry Atoms, Elements and How They Behave

Start Small End Big Atoms  Elements  Compounds  Cells  Tissues  Organs  Organ Systems  Organisms

What is Matter? Matter occupies space and has mass Mass is the quantity of matter Chemical changes in matter are essential to all life processes

Smallest amount of an element that still has the properties of that element. Made up of: - Protons, P +, Charge of +1 - Neutrons, N, zero charge - Electrons, e -, charge of -1 ATOM:

Structure of an Atom P P N N e e Nucleus: Center of atom, where protons and neutrons are located Orbital: Area outside nucleus where electrons are in constant motion

Orbits spin and rotate in three dimensions. P P N N e e Structure of an Atom

Each Orbit is a specified distance from the nucleus. P P N N e e Structure of an Atom

P P N N e e Nucleus Orbit e e e e e e e e e

Each type of atom has its own number of e, P and N P P N N e e Structure of an Atom

The different combination of P, N and e make each element unique P P N N e e Structure of an Atom

Normally, all the “+” of the protons and the “-” from the electrons balance out and the overall charge of the atom is zero. Structure of an Atom

What if an atom loses an electron? P P N N e Structure of an Atom P P N N e e Atom becomes positive

P P N N e e Structure of an Atom What if an atom gains an electron? - Atom becomes negative e -

Any charged atom is called an ion Structure of an Atom - Positive ions are called cations - Negative ions are called anions

Structure of an Atom Isotopes: atoms of the same element that have different numbers of neutrons Stable He atom - has 2 protons and 2 neutrons - atomic mass = 4 Isotope of He - has 2 protons and 3 neutrons - atomic mass = 5

The Periodic Chart Atomic number is the number of protons Atomic Mass is the “approximate” number of protons + neutrons Assume Electrons = Protons (except Ions)

Atomic Mass = Protons + Neutrons Why don’t the electrons figure in?

Drawing Atoms: Each orbit can hold a maximum number of electrons. - Orbit 1: holds a max of 2 - Orbit 2: holds a max of 8 - Orbit 3: holds a max of 8 You must fill the inner orbits before adding electrons to the outer orbits.

Examples 15 P 31

Examples 9 F 20

Main Elements in Human Body Oxygen Carbon Hydrogen Nitrogen

Main Elements in Earth’s crust Oxygen Silicon Aluminum Iron

How do atoms “stick” together? ….Using BONDS! Bonds are forces of attraction between atoms Bonds occur because of electrons.

Bonding Atoms like to be stable. Unstable atoms react with other atoms. Atoms become stable by bonding 2 types of bonds Ionic Bonds Covalent Bonds

Types of Bonds Ionic Bond- One atom gives an electron to the other

IONIC: Creates opposite charge that holds atoms together

Types of Bonds Covalent- each atom shares electrons with the other

Valence electrons Electrons in outer most orbit Atoms want a complete outer orbit They will bond with atoms that fill the orbit

Examples Look at the column on periodic table to figure out Valence electrons Na __________ Cl ____________ Total: _______________ bond?

Examples Look at the column on periodic table to figure out Valence electrons C __________ N____________ _______________ bond?

Compounds Two or more atoms bonded together in a set proportion H 2 0 vs. H 2 O 2 - what is different? C0 2 vs. CO

Compounds Parts are chemically bound together Definite proportions required Properties of a compound are chemically and physically different from the properties of the elements that make up that compound

Mixtures Mixtures have “ingredients” that do not bind chemically with each other Each ingredient keeps its own properties Definite proportions not required Types: solution, suspension, colloid

Mixtures Solution: homogeneous; even throughout; solute (substance) completely dissolves in solvent (liquid) Suspension: Heterogeneous; looks even if shaken; but particles settle to bottom

Mixtures Colloid: heterogeneous BUT does not settle; sort of in between the other two.

Mixtures vs. Compounds Look at your notes: What are three big differences between Mixtures and Compounds?

Chemical Reactions Change in the arrangement of atoms that creates a different substance A + B  C synthesis reaction A  B + C decomposition A + B  C + D neutralization

Exothermic and Endothermic Reactions on the previous page can be either exothermic or endothermic. Draw the graphs of exothermic and endothermic and provide examples of reactions.

Chemical Reactions Reactants: The “stuff” you start with Products: The “stuff” you end up with A + B  C ReactantsProducts

Chemical Reactions 8Fe + S 8  8FeS synthesis H 2 0  H + + OH - Decomposition

Properties of Water Water is held together with special covalent bond called polar covalent bond - Means water has poles, or ends. - O is the negative end - H’s are the positive end

Oxygen doesn’t share electrons evenly with Hydrogen! (think how older siblings “share” with younger siblings!)

Properties of Water Water is POLAR! Molecules are electrically neutral. Portions of a molecule can act as though they have an electrical charge if the components have different attractions for electrons.

Properties of Water Cohesion: Water molecules stick together because of charges Polar molecules with hydrogen atoms are very strongly attracted to the negative regions of other polar molecules (like water).

Cohesion Creates Surface tension - allows stickbugs to walk on water!

Adhesion OR..water molecules can stick to other charged substances like glass Glass stirring rod

Other properties Capillarity Allows water to be drawn up into a narrow tube Due to cohesion and adhesion High heat capacity Allows water to take in a lot of energy, without a large change in temperature (beach in the summer).

Water is the Universal Solvent Anything with a charge will attract water molecules and dissolve Ionic and polar molecules have charge Water dissolves more substances than any other solvent…but CANNOT dissolve everything! Nonpolar molecules (like fat) do not have charge and will not dissolve

Other important chemical reactions Oxidation – reduction reactions Look in the handout that contained Ecosystem recycling Look for compounds adding and losing hydrogen and oxygen ions. These reactions MOVE ENERGY (by transferring electrons) Energy pyramid Biogeochemical cycles

Chemical Reactions Oxidation Reduction Reactions In these reactions one reactant loses an electron and one reactant gains an electron Na + Cl 2  2NaCl The reactant that loses an electron is oxidized. The reactant that gains an electron is reduced.

Neutralization Reactions Help living things to maintain pH (this is important to keep all chemical reactions working

Chemical Reactions Neutralization Reaction Occur between Acids and Bases and form a salt and water NaOH + HCl  NaCl + H 2 0 Base Acid

Acids Acids: a chemical that when dissolved in water releases a hydrogen ion (H + ) HX (in water)  H + + X -

Properties of Acids Taste sour – think of lemon Turn litmus paper from blue to red Corrodes Metal Examples: Sulfuric Acid, Lemon Juice, Battery Acid

Bases Base: a chemical that when dissolved in water releases a hydroxide ion (OH - ) XOH (in water)  OH - + X +

Properties of Bases Taste bitter – cough meds. Turn litmus paper back to blue after acid turns it red Can cause serious burns Examples: Bleach, KOH, NaOH

Acids and Bases - Examples NaOH + H 2 O  Na + + OH - + H 2 O HCl + H 2 O  H + + Cl - + H 2 O

Acids and Bases will “cancel” each other out When an Acid and a Base are mixed together they will “Neutralize” each other and create Water and a Salt This is a Neutralization Reaction

Neutralization Reaction HCl + NaOH  NaCl + H 2 O A Salt Water HNO 3 + KOH  KNO 3 +H 2 O A salt Water

Concept of pH pH = power of Hydrogen pH = power of Hydrogen A way of measuring how many Hydrogen ions, H+, there are in a solution A way of measuring how many Hydrogen ions, H+, there are in a solution Determines whether a solution is an acid or a base Determines whether a solution is an acid or a base

Neutral (water) AcidBase High H + Low OH - H + = OH - High OH - Low H + pH Scale – a measure of the concentration of Hydrogen Ions

Concept of pH Where is the “safe” pH? Where is the “safe” pH? pH must stay between in the human body Another factor that must maintain homeostasis

Concept of pH Are there exceptions? Are there exceptions? Stomach is acidic ( digest proteins ) Intestines are basic ( digest fats ) Buffers are necessary weak acids or bases that react with strong acids or bases to prevent sudden changes in pH

What is the pH of Rain water?? Usually between (not 7!) - Water reacts with CO 2 in air to form Carbonic Acid (H 2 CO 3 )

What is the pH of Rain water?? Acid Rain: - Rain water reacts with pollutants such as sulfur dioxide (SO 2 ) and Nitrogen oxides (NO and NO 2 ) in air - Forms Sulfuric Acid, Nitric Acid, Ammonium Sulfate - Decreases pH to below 5.5!

Cleaning and pH – depends on the job Type of cleanerpH rangeSoils Mineral-acid cleaner0-2Heavy oxide scales Mild acid2-5.5 Inorganic salts, water soluble metal complexes Neutral Light oils, small particles Mild alkaline8.5-11Oils, particulates, film Alkaline Oils, fats, proteins Highly alkaline Heavy grease/soils