General Chemistry Lecture

General Chemistry • • • • • • • Ground Rules for Lectures Arrive on time. Listen actively and attentively. Mask must be worn. Keep the distance between you and your colleague. Bring something to write with and in. Turn your cell phone off. Do not leave class early without okaying it with the instructor in advance. • Ask questions if you are confused. • Try not to distract or annoy your classmates Chemistry The study of the composition, structure and properties of substances under different conditions. Branches in Chemistry and their Importance - Organic Chemistry The study of chemicals that contain carbon. Importance of Organic Chemistry • Doctors • Surgeons • Dentists • Pharmacists • Lab technicians • Oil and gas analysis - Inorganic Chemistry The study of chemicals that do not contain carbon. - Importance of Inorganic Chemistry • Medical industry and healthcare facilities. • The usage of salt in our daily lives. • Ceramic industry. • Electric circuits. - Analytical Chemistry - Identification of composition of matter. - Identification of compounds. Importance of Analytical Chemistry • Medicine- measurement of vital nutrients such as carbohydrates, proteins, and sugars in the human body. • Determination of harmful waste levels in the body, such as uric acid, cholesterol, and salts. Mass Spectrometer Gas Chromatograph - Physical Chemistry The study of: • The mechanism. • The rate. • The energy transfer that happens when matter undergoes change. - Importance of Physical Chemistry • Discovering, testing, and analyzing them like solid, liquid, or gas. • Analyze materials with advanced instruments such as lasers and microscopes. - Biochemistry • Study of processes that take place in organisms. • Understand the structure of matter found in the human body and the chemical changes that occur in cells. - Importance of Biochemistry • Food science. • Agriculture. • Chemistry in Clinical Practice. Anything that has mass and takes up space. Substances exist in any of the following distinct states: • Solids • Liquids • Gases Atomic structure - Dalton’s Atomic Theory (1808) 1. Elements are composed of small particles called atoms. 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements. 3. Compounds are composed of atoms of more than one element. 4. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction . - An ion is an atom or group of atoms that carries an electrical charge. - An anion is a negatively charged ion. - A cation is a positively charged ion. - Electrolytes are substances that conduct electricity when dissolved in water, or when melted if they don’t dissolve. Those that don’t are nonelectrolytes. Rutherford’s Experiment (1908 Nobel Prize in Chemistry) α particle velocity ~ 1.4 x 107 m/s (~5% speed of light) Mass of proton is 1840 x mass of electron (1.67 x 10-24 g) Mass p ≈ mass n ≈ 1840 x mass eParticle Charge Location Proton Relative mass 1 + Inside the nucleus Neutron 1 Neutral (no charge) Inside the nucleus Electron 1/1800 - In space surrounding nucleus Atomic number, Mass number and Isotopes Atomic number (Z) = Number of protons in nucleus Mass number (A) = Number of protons + Number of neutrons = Atomic number (Z) + Number of neutrons Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei. Number of neutrons= Mass number- Atomic number A periodic table Metals have characteristic physical properties such as: - Efficient conduction of heat and electricity. - Malleability (they can be hammered into thin sheets). - Ductility (they can be pulled into wires). - Lustrous appearance. - Chemically, metals tend to lose electrons to form positive ions (Cations). - The nonmetals lack the physical properties that characterize the metals. Chemically, they tend to gain electrons in reactions with metals to form negative ions (Anions). Nonmetals often bond to each other by forming covalent bonds. For example, chlorine is a typical nonmetal. Under normal conditions it exists as Cl2 molecules; it reacts with metals to form salts containing Cl- ions (NaCl, for example); and it forms covalent bonds with nonmetals (for example, hydrogen chloride gas, HCl). The periodic table is arranged so that elements in the same vertical columns (called groups or families): - All of the alkali metals, members of Group 1A—lithium (Li), are very active elements that readily form ions with a 1+ charge when they react with nonmetals. - The members of Group 2A—beryllium (Be), are called the alkaline earth metals. They all form ions with a 2+ charge when they react with nonmetals. - The halogens, the members of Group 7A—fluorine (F), form diatomic molecules (F2). Fluorine, react with metals to form salts containing ions with a 1- charge (F-). - The members of Group 8A—helium (He), known as the noble gases. It exist under normal conditions as monatomic (single-atom: He) gases and have little chemical reactivity. - The symbols 1A through 8A are the traditional designations, whereas the numbers 1 to 18 have been suggested recently. The groups labeled 1A through 8A are often called the main groups. - The horizontal rows of elements in the periodic table are called periods. Horizontal row 1 is called the first period (it contains H and He); row 2 is called the second period (elements Li through Ne); and so on. Bohr’s Model of the Atom (1913) • e- can only have specific (quantized) energy values. light is emitted as e- moves from one energy level to a lower energy level. En = -RH (1/n2 ) n (principal quantum number) = 1,2,3,… RH (Rydberg constant) = 2.18 x 10-18 J Quantum numbers (n, l, ml, ms) Principal quantum number (n) )1 n = 1, 2, 3, 4, …. distance of e- from the nucleus n=1 n=2 n=3 Angular momentum quantum number (l) )2 for a given value of n, l = 0, 1, 2, 3, … n-1 n = 1, l = 0 n = 2, l = 0 or 1 n = 3, l = 0, 1, or 2 l=0 l=1 l=2 s orbital p orbital d orbital Shape of the “volume” of space that the e- occupies l = 0 (s orbitals) l = 1 (p orbitals) l = 2 (d orbitals) Magnetic quantum number (ml) )3 4) Spin quantum number (ms) ms = +½ ms = -½ Pauli exclusion principle - no two electrons in an atom can have the same four quantum numbers.