Chemistry Exam Study Guide - Hidetoshi Azuma PDF

Chemistry Exam day: 16 December 2024 Matter and Change Chemistry is a physical science 1. What is chemistry a. Natural sciences were once divided into two major categories: biological and physical science. i. Biological sci...

Chemistry Exam day: 16 December 2024 Matter and Change Chemistry is a physical science 1. What is chemistry a. Natural sciences were once divided into two major categories: biological and physical science. i. Biological science: focuses mainly on living things ii. Physical science: focuses mainly on non-living things 1. Both Biological and Physical consists of chemical structures 2. Chemistry is central to all sciences, and there are no divisions between biological and chemical sciences b. Chemistry is the study of the composition, structure, and perspective of matter, the process that matter undergoes, and the energy changes that accompany these processes. c. Branches of chemistry include: Organic Chemistry: study of chemicals containing carbon. Inorganic chemistry: study of chemicals with no carbon. Physical Chemistry: study of properties of matter about energy. Analytical Chemistry: study that focuses on composition matters. Biochemistry: study of processes that take place in organisms. Theoretical Chemistry: study of chemical behavior using mathematics and computers. d. Teflon’s case study i. Basic research: Increases knowledge (why specific reaction occurs) ii. Applied research: Solves a problem (Development of new refrigerants) iii. Technological research: Improves quality of life (the production, use of products) Examples: A laboratory in a major university survey all the reactions involving bromine = Basic A pharmaceutical company explores disease to produce a better medicine = Applied A chemical company develops a new biodegradable plastic = Technological Matter and its properties Matter: Anything that has mass or volume Mass: A measure of the amount of matter Volume: Amount of three-dimensional space an object occupies a. Building blocks of matter Atom: Smallest unit of an element that maintains the identity of an element Pure substance: Has fixed composition (same characteristics properties, composition) Element: A pure substance that cannot be broken down into simpler substances Compound: A pure substance that can be broken down into simpler substances Molecule: Smallest unit of an element that retains all the properties of that element Mixture: A blend of two or more kinds of matter, which retain its identity/properties Homogeneous: A mixture that has a uniform composition (ex: salt water) Heterogeneous: Mixtures that are not the same throughout (ex: stew) b. Properties of Matter i. All substances have characteristics properties Extensive properties: Depends on the matter present (includes: Volume, mass, amount of energy) Intensive properties: Do not depend on the matter present (includes: melting/boiling point, density, ability to conduct electricity, and transfer energy as heat) Physical properties: characteristics that can be observed or measured without changing the identity of a substance (Melting point, boiling point, density) Physical change: change in a substance that does not involve a change in the identity (cutting) Chemical properties: Undergoes changes and transforms into different substances Chemical change: when substances are converted into different substances (burning) The substance that reacts in a chemical reaction is called reactants. The substances that are formed by the chemical change are called products.  c. States of Matter i. Solid: has definite volume and shape ii. Liquid: had definite volume but indefinite shape iii. Gas: has neither definite volume nor definite shape iv. Plasma: High-temperature physical state of matter in which atoms lose most of their electrons. Elements The periodic table Vertical columns are called groups Horizontal rows are called periods There are 18 groups and 7 periods 1. Atomic number a. Atomic number is the same number of protons in the nucleus of an atom b. Also the same as the number of electrons around the nucleus of an atom i. As you move across, the atomic number increases ii. As you move down, the atomic number increases 2. Atomic mass a. Atomic mass is the combined number of protons and neutrons in the nucleus. i. Also called atomic weight ii. Does not include the mass of electrons iii. As you move down or go across the table, the atomic weight increases 1. Except for Tellurium (Te) is heavier than iodine (I) 3. Metals, non-metals, and metalloids a. Metals: Lustrous, solid, malleable, ductile, and highly conductive in heat and electricity. b. Non-metals: More than half of no-metals are gaseous at normal temperatures i. Tends to be brittle, and poor conductor of heat and electricity c. Metalloids: Exist between metals and non-metals i. A little bit brittle and semiconductors Measurements and Calculations 1. Qualitative and quantitative observations a. Qualitative: measuring or counting something (with numbers and statistics) b. Quantitative: describing something in numerical terms (appearance, color) 2. Scientific notation a. Scientific notation is a way of writing small or large numbers b. Decimal moved to the right of the exponent will be negative i. Ex.: 0.00000000875 = 8.75 x 10^-9 c. Decimal moved to the left of the exponent will be positive i. Ex: 8751000000 = 8.75 x 10^9 3. Significant figures a. Significant figures of a number are the digits that have meaning to the value of the number i. Important for scientists to not give measurements that are more accurate than what's stated on the equipment. b. Basic rules to tell they are significant i. All non-zero digits are significant ii. Any zeros between significant digits are also significant iii. Trailing zeros to the right of a decimal point are significant iv. The only digits that aren’t significant are zeros which act as a placeholder in a number v. All non-zero numbers (1,2,3,4,5,6,7,8,9) are always significant vi. All zeroes in the beginning never count vii. All zeros in the middle of non-zero numbers are always significant viii. Zeroes at the end count only if there is a decimal point  c. Accuracy and Precision, calculate density i. Accuracy: Whether it’s hitting the target ii. Precision: How close the arrows are to each other iii. Calculating density: Density=mass divided by volume Dimensional analysis Atoms the building blocks of matter 1. 5 principles of Dalton’s atomic theory a. Elements are made up of small particles called atoms b. Atoms of a given element are identical in size, mass, and other properties c. Atoms of different elements are different in size, mass, and other properties d. Atoms cannot be subdivided, destroyed, or created e. Atoms of different elements combine in a simple whole-number ratio to form chemical compounds f. In chemical reactions, atoms are combined, rearranged, or separated. i. THE 2 IN RED WERE PROVEN TO BE WRONG 2. Law of conservation of mass, definite proportions, and multiple proportions a. Law of conservation of mass: mass is neither created nor destroyed during ordinary chemical reactions and physical changes. b. Law of definite proportions: a chemical compound contains the same element in the same proportions by mass regardless of the size of the sample. c. Law of multiple proportions: if 2 or more different compounds are composed of the same 2 elements, then the ratio of the mass of the second element combined with a certain mass of the first element is always a ratio of small whole numbers. 3. Atomic number, atomic mass, mass number, and isotopes a. Atomic number: the number of protons in an atom (determines the identity of an element) b. Atomic mass: the standard used to compare units of atomic mass is the carbon-12 atom, which has a mass of exactly 12 atomic mass units. i. 1 unified atomic mass unit, or 1u, is exactly 1/12 the mass of carbon-12. c. Mass number: the number of protons and neutrons d. Isotopes: atoms with same number of protons but different number of neutrons. i. Atoms with same atomic number but different mass number.  4. Atoms, protons, electrons, and neutrons a. Atoms: the basic building blocks of matter i. Made up of: 1. Nucleus (center) 2. Protons (positive particles) 3. Electrons (negative particles) 4. Neutrons (particles with no charge) b. Protons: a subatomic particle with a positive electrical charge c. Electrons: a subatomic particle with a negative electrical charge d. Neutrons: a subatomic particle with no charge Counting atoms Mole: SI unit for the amount of substance (certain number of things; sometimes called the chemist’s dozen) A mole is 6.02 x 10^23 things !!!!! 1. Mole, and Molar mass a. Mole: amount of substance that contains as many particles as atoms in exactly 12 grams of carbon - 12. b. Molar mass: mass of 1 mol of a pure substance i. Molar mass units = g / mol ii. The molar mass of an element is numerically equal to the atomic mass of the element and unified atomic mass units. (Can be found in the periodic table) iii. The molar mass of an element contains one mole of atoms 1. Ex: 4.00 grams of helium, 6.94 grams of lithium, and 200.59 grams of mercury all contain a mole atom. 2. Count atoms a. Average atomic mass of isotopes: BE ABLE TO CALCULATE: 1. Mole to grams conversion 2. Grams to mole conversion 3. Grams to atom conversion The development of a new atomic model/Quantum model of an atom Electron Configuration: the arrangement of electrons in an atom Electrons tend to assume the arrangements that give the atom the lowest possible energy because low-energy systems are more stable than high-energy systems. 1. Electron configuration, Noble gas notation, and Orbital notation a. Electron configuration notation: 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², 4f¹⁵, 5d¹⁰, 6p⁶, 7s², 5f¹⁵, 6d¹⁰, 7p⁶ b. Noble gas notation: [Ne]3s², [Ne]3s² c. Orbital notation: ⇅⇅⇅⇅⇅⇅⇅⇅ (red is 1s, 2s, and orange is 3p which is a triple pair. Fill them up first before filling them down) 2. Hund’s rule, Aufbau principle, and Pauli’s exclusion principle a. Hund’s rule: Electrons repel each other, because they have negative charges i. The electrons must be placed into the orbitals so that no pairs are put together unless absolutely necessary. b. Aufbau principle: each electron occupies the lowest energy orbital available. i. The Aufbau diagram arranges their atomic orbitals from lowest energy to highest. c. Pauli’s exclusion principle: electrons come in 2 varies based on their spinning direction. i. There is an UP and DOWN spin ii. UP and DOWN spins are always paired together (UP-UP or DOWN-DOWN combinations are not allowed) 3. Bohr’s model of the atom How many electrons can go in each orbital? : 2 electrons Quantum numbers Who noticed that when the elements are arranged in order of increasing the atomic mass? : Mendeleev The ancient Greek natural philosopher who first proposed the notion of the atom was? : Democritus 1. Principal Quantum Number (n) n= 1,2,3 etc It is described as the average of electrons in the nucleus The larger the value, the further from the nucleus 2. Angular Momentum Quantum Number (L) Shape of the orbitals (sublevels) Depends on the orbitals 3. Magnetic Quantum Number (m¹) Orientation of the orbital in 3-D space -1…………..0…………….+1 When L=0, m¹= 0 When L=1, m¹= -1, 0, +1 When L=2, m²= -2, -1, 0, 1, 2 4. Spin Quantum Number (m²) Electrons spin in 2 directions only Always valued at +½ or -½ The +½ corresponds to the UP spin of the electron The -½ corresponds to the DOWN spin of the electron 5. Calculate n, L, m¹, m² Chemical bonding, Valency, and Charges 1. Ionic Bonding, Covalent bond, and Octet rule a. Ionic bonding: Involves a transfer of electrons. i. One element loses electrons and the other gains electrons. ii. Forms the attraction between + and - ions iii. Ionic compound is made up of crystals 1. Crystals: consists of 3D, repeating patterns of alternating + and - ions. b. Covalent bond: Involves a sharing of electrons. i. Atoms will share to reach a stable electron configuration c. Octet rule: Atoms will lose or gain electrons to become isoelectronic with a noble gas. 2. Valence electrons, and Electron dot a. Valence electrons: Electrons located in the outermost energy level i. Is responsible for bonding electrons b. Electron dot: Way to show the number of valence electrons in an atom 3. Charges a. The charges are the + or - notation of an element. i. The question for this will be similar to the quiz: ii. Example: What charge will Al have when it loses or gains electrons? : +3