Basic Chemistry

Chemistry Warm-Up a. Compound b. Molecule c. Proton d. Neutron e. Electron f. Ion g. Isotope h. Atom i. Element j. Nucleus 1. negatively charged sub-atomic particle 2. A charged particle 3. Positively charged sub-atomic particle 4. Contains protons and neutrons 5. 2 or more atoms bonded together 6. Atoms of different elements bonded together 7. Neutral sub-atomic particle 8. Atoms with equal # of protons, but different # of neutrons 9. The smallest particle of an element 10. Substance composed of 1 type of atom

Matching Answers a. Compound - Atoms of different elements bonded together (6) b. Molecule - 2 or more atoms bonded together (5) c. Proton - Positively charged sub-atomic particle (3) d. Neutron - Neutral sub-atomic particle (7) e. Electron - negatively charged sub-atomic particle (1) f. Ion - A charged particle (2) g. Isotope - Atoms with equal # of protons, but different # of neutrons (8) h. Atom - The smallest particle of an element (9) i. Element - Substance composed of 1 type of atom (10) j. Nucleus - Contains protons and neutrons (4)

Atom – the smallest unit of matter “indivisible” Helium atom Contains 3 sub-atomic particles Protons ( p+): Mass = 1 Neutrons (N0): Mass = 1 Electrons (e-): Mass = 0

Atom Atomic Number - # of protons in an atom Atomic Mass - # of protons and neutrons in an atom. C 6 Carbon Atomic # Atomic mass Chemical Symbol

Learning Check Look at your Periodic Table and determine the number of protons, neutrons, and electrons for the following atoms: Nitrogen Lithium Hydrogen Fluorine

What are living things made of?

Why do we need these? These atoms make up the molecules of life. Many act as vitamins and minerals, help our cells carry out important reactions.

Isotopes – Who Cares?! Same # protons (same element, same exact chemical behavior) different # neutrons Some isotopes are radioactive – Nucleus is unstable. Spontaneously gives off energy (radiation)

Isotopes Medical Uses Tracers and Labels Ex: Iodine 131 – Behaves exactly like I 127. Moves through human body and accumulates in thyroid. Half-life of 8 days. Gives off energy, so presence can be detected. Ex: PET scan

Isotopes Half-Life: Time it takes for ½ atoms in a sample to decay Can be used to determine age of rocks, fossils, etc. Carbon-14 is radioactive. ½ Life = 5,730 years.

Electron Shells a) Atomic number = number of Electrons b) Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells. c) Electron shells determine how an atom behaves when it encounters other atoms

Electrons are placed in shells according to rules: 1) The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons. 2) “The Octet Rule”: Atoms will gain or lose electrons in order to have a filled outer shell. (Most stable state)

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons Predict: How many electrons will these atoms lose/gain?

Why are electrons important? 1) Elements have different electron configurations  different electron configurations mean different levels of bonding (and different chemical properties)

Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons H  He:            Li  Be   B   C   N   O  : F  : Ne :                    Na  Mg   Al   Si   P   S  : Cl  : Ar :        

Learning Check A. X would be the electron dot formula for 1) Na2) K3) Al B. X would be the electron dot formula 1) B2) N3) P

Dmitri Mendeleev The Periodic Table of the Elements

The Periodic Table A map of the building block of matter.

Layout of the Periodic Table: Metals vs. nonmetals Metals Nonmetals

Across the Periodic Table Periods: Horizontal rows (1-7) These elements have the same number of valence shells. 2nd Period 4th Period All of these have 4 energy levels

Down the Periodic Table Family: Are arranged vertically down the periodic table (columns or group, or 1-8 A,B) These elements have the same number of valence electrons Alkali Family: 1 e- in the valence shell Alkali Family: 1 e- in the valence shell Halogen Family: 7 e- in the valence shell Halogen Family: 7 e- in the valence shell Alkali Halogen

Periodic Table: electron behavior Elements in the periodic table can be classified by the behavior of their electrons Metals MetaloidsNon-Metals

Learning Check A. Number of valence electrons in aluminum 1) 1 e - 2) 2 e - 3) 3 e - B. Change in electrons for octet 1) lose 3e - 2) gain 3 e - 3) gain 5 e - C.Ionic charge of aluminum 1) 3- 2) 5- 3) 3 +

Atomic Bonding Atoms can form several types of bonds Covalent Ionic Hydrogen Molecules - Atoms covalently bonded together Compounds – Atoms of different elements bonded together

Ionic Bond Between metals and nonmetals Bond formed by transfer of electrons Produce charged ions Examples; NaCl, CaCl 2, K 2 O

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

Covalent Bond Between 2 nonmetals Formed by sharing electron pairs Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC I want more electrons No I want more electrons! Let’s share

2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Molecule (O 2 ) Oxygen Molecule (O 2 ) Water Molecule (H2O)

There are other ways of representing covalent bonds.

Quick Check Question For each of the following element pairs, determine whether a covalent bond or an ionic bond is likely to form. K and S Be and F Li and I O and O

Any Questions? Next we will make some paper molecules. Each group will make a different molecule or compound so that we can see a variety. CO 2, H 2 O, CH 4, O 2, N 2, NH 3, H 2, LiF, HCl Step 1: Determine the type of bond in each molecule/compound Step 2: Cut out the atoms and electrons you will need and glue them onto construction paper Color and label

when electrons are shared equally NONPOLAR COVALENT BONDS H 2 or Cl 2

2. Covalent bonds- Two atoms share one or more pairs of valence electrons. Oxygen Molecule (O 2 ) Oxygen Molecule (O 2 )

Aside from single covalent bonds, double, or triple covalent bonds can form. A double bond… how many electrons are shared? 4e- A triple bond…. How many electrons here? 6e-

when electrons are shared but shared unequally H2OH2O POLAR COVALENT BONDS

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

Hydrogen Bonds Partially charged ends of polar molecules are attracted to neighboring molecules. Gives water its special properties.

Water and Living Things Water is the most abundant molecule in living things. Water has special traits that make it important to life.

Properties of Water Hydrogen bonding between polar molecules causes water to “stick together” Adhesion Cohesion Capillary Action Surface Tension Excellent Solvent High Specific Heat Frozen water is less dense so ice floats

Properties of Water Adhesion Cohesion Surface Tension

Capillary action helps carry water to the tops of tall trees

Water expands as it freezes Why is this important for life? Ice Water Steam

Water as a Solvent

Chemical Reactions Involves making and breaking chemical bonds Necessary for cells Build molecules for growth and maintenance Store/release energy metabolism

Chemical Reactions Forming and breaking of bonds. Necessary for cells Build molecules for growth and maintenance Store/release energy Reactants Products Breakdown of H2O: 2H 2 O2H 2 + O 2 Photosynthesis: 6H 2 O + 6CO 2 C 6 H 12 O 6 + 6O 2 Electrical energy Light energy Balanced equations: represents conservation of matter!

Ions Salts dissociate in water – result is ions NaCl  Na+ and Cl- Polar H 2 O molecules attract, dissolve ions

pH Ionization: non-polar molecules are converted to ions H 2 O  H + and OH - In a sample of water, a small percent of molecules are always ionized

pH Levels of H + and OH in solution rated using pH scale. Equal H + and OH -  pH of 7 (ex: pure water) Logarithmic scale – each level has 10x more H + or OH - than previous

Acids are molecules that release hydrogen ions in solution. HCl  H + + Cl -

Bases are molecules that either take up hydrogen ions or give off hydroxide ions in solution. NaOH  Na + + OH -

Water dissociates and releases hydrogen ions (H + ) and hydroxide ions (OH - ). An equal number of H+ and OH- So that’s why water is neutral!

pH Crucial to living things. Enzyme Function Acidic stomach, Alkaline intestine Blood pH = 7.4 Buffers in living things help resist pH change

Buffers are substances that help to resist change in pH.