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Unit 2- Early Theories Early Scientists: (450 B.C.) Earth, Water, Air, and Fire: The Four States of Matter The ancient Greek philosophers’ curiosity sparked the interest of scholarly thinking. They speculated about the nature of matter, and formulated explanations of matter based on their own life experience. Therefore they believed that there are four elements that everything is made up of: earth, water, air, and fire. This theory waslater be supported and added to by Aristotle who was more beloved and therefore able to persuade people from believing in Democritus atoms. (Aristotle also suggested that there was a fifth element, aether, because it seemed strange that the stars would be made out of earthly elements. He would be surprised to learn that they are in fact made up of many elements found on earth, and are so hot they could be said to be on fire all the time!) According to Aristotle atoms could not exist because they would have to move through empty space, and empty space could not exist. These idea that these four elements earth, water, air, and fire - made up all matter was the cornerstone of philosophy, science, and medicine for the next two thousand years. Everything visible was made up of some combination of earth, water, air, and fire Democritus: (460-370 B.C.) Democritus was an ancient Greek philosopher who is an influential pre-Socratic philosopher and pupil of Leucippus, who formulated what, is thought to be the first atomic theory. Some people consider him to be the father of modern science. Democritus claimed that everything is made up of what he called atomos, later becoming the English word atoms. His ideas were based on reasoning rather than science. He reasoned that if you cut a stone in half, each half had the same properties as the original stone. He theorized that there are an infinite number of atoms and kinds of atoms, which differ in shape, and size. Through reasoning he stated that if you continued to cut the stone into smaller and smaller pieces, at some point you would reach a piece so tiny that it could no longer be divided. Using analogies from our senses, you give us an image of an atom that distinguished them from each other by their shape, size, and the arrangement of their parts.. Your model (or The Democritean atom) is an inert solid that interacts with other atoms mechanically. Antoine-Laurent Lavoisier: He is recognized as the father of modern chemistry. He believed that matter was neither created nor destroyed in a chemical reaction, and sought to prove that hypothesis. He performed some of the first quantitative chemical experiments. He studied the thermal decomposition of mercury (II) oxide, which is a powdery red solid. When the solid is heated it reacts to form 1 silvery liquid mercury and colorless oxygen gas. He intelligently performed the reaction in a closed container so that the gas could not escape. Curious he did experiments with many other gases including hydrogen and oxygen. Upon inserting a match in the glass container containing the two, he observed the formation of water. In conducting other experiments you observed that when new substances were made the mass from the original substances were the same as the new substances. The data from his experiments led to the making of the law of conservation of mass. The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. Joseph Proust: Proust was a French chemist who lived in the 1700s and worked most of his life as a teacher. Although he had no understanding of the atom, he believed that substances always combined in definite proportions. His significance to the modern atomic model however came by analyzing different sources of compounds; he found that they always contained the same ratio by weight of their elements. Such as when reacting hydrogen with oxygen, he noticed that water is always composed of 11% hydrogen and 89% oxygen by mass. Also table salt always contained 1.5 times as much chlorine as sodium. This led to the Law of Definite Proportions. The Law of Definite Proportions states that the ratio by mass of the elements in a chemical compound is always the same regardless of the source of the compound. John Dalton: (1803) John Dalton, an observer of weather and discoverer of color blindness among other things, was the first scientist to explain the behavior of atoms in terms of the measurement and weight. By studying Democritus’s work Dalton became fascinated with atoms and sought to expand his theory. He believed that different atoms or elements could be distinguished by their weight. While working on your theory you discovered the law of multiple proportions which states that when combining two or more elements to form a chemical compound, the elements are always in the smallest whole number ratios. This ground breaking research lead to Dalton’s Atomic Theory which had 5 basic principles: 1. All matter is made up of tiny indivisible spheres (atoms). 2. All atoms of one element are exactly alike, but they are different from atoms of other elements. 3. Atoms of different elements have different physical and chemical properties. 4. Atoms of different elements combine in simple whole number ratios to form compounds. 5. Atoms cannot created or destroyed in a chemical reaction. Your billiard ball model of the atom was the first model that was widely accepted as what we now call atoms. Even though your ideas are similar to Democritus’s people accepted your ideas. 2 Unit 2- Subatomic Particles 1. The electron a. _______________ Tube experiment in 1897 i. Completed by _______________________ ii. Atoms not neutral spheres, composed of _____________ particles iii. Electrons (_________) iv. Calculated mass to be ________________________ grams Cathode Ray Tube Thompson’s Plum Pudding Model of the atom b. __________________ oil drop experiment i. Used x-rays to place a charge on ___________droplets ii. Applied an exact voltage to_______________ charged oil droplets iii. Used this to determine the exact charge of an ______________ 1.6 x 10-19 C. 3 2. Eugen Goldstein i. Observed rays in a ______________tube traveling from the ___________to the cathode. ii. These were deflected towards the __________________plate. iii. Protons! (_______) =______________________grams iv. Elements seemed to be comprised of an even number of electrons and protons. 3. Neutrons a. Not discovered until 1932 by _______________ _________________ i. ______________charged particles ii. (n0) = ____________________ grams iii. Accounts for _________________- atoms of an element that are chemically alike but differ in _______________. b. Isotope notation: 𝑦 𝑧𝑋 i. ______ is the atomic symbol _________is the mass number, and _____is the atomic number ii. Atomic number = number of ___________________ iii. In a neutral atom the number of protons equals the number of ____________ iv. Mass number = number of ___________+_____________ v. Atomic Mass unit (_______) is equal to the mass of __________ proton or neutron 1. Example: 4 Nuclear Stability 1. How elements are created a. Elements from 1-92 were _______________ created. b. All elements from 2-26 were formed through _________________by stars c. All others are created through nuclear reactions. 2. Nuclear Reactions a. Involve a ____________ in the _________________ of an atom b. Occur because the nucleus of an atom is ____________________ i. Inside an atom 1. Two subatomic particles make up the nucleus the _______________ and the ________________ 2. As the number of protons increase, there are more _______________ within the nucleus. 3. _____________________ help by acting as buffers to decrease the repulsive _________________ between protons. 3. Stability of the nucleus a. Whether a nucleus of an atom is stable or unstable depends on the ____________ of protons to neutrons in the nucleus. b. This is called the N: Z ratio where N is the number of _____________ an isotope has and Z is the number of __________________ an isotope has. i. Isotopes of the same element have the same number of _______________ and different number of ____________________. ii. For element > # 20 the ratio of N:Z needs to be ___________ for the isotope to be stable. iii. For elements 20-83 the ratio of N:Z needs to be ______________for the isotope to be stable. 1. Example: 12 a. C and 14C b. 130 Xe and 141 Xe 5 iv. The graph shows the band of ______________, if it is not with in the band then the nucleus is unstable and will __________________ to a new element. 4. Types of nuclear decay a. Alpha emission i. Occurs when there are too many ______________ in the nucleus ii. An alpha particle is emitted 1. An _______________ particle is the nucleus of a helium atom without any electrons = ___________________ iii. Example: b. Beta emission i. Occurs when there are too many ___________________ in the nucleus ii. A neutron _______________ into a proton and a beta particle is ejected from the nucleus. 1. A beta particle is an ____________ = −10𝛽 or −10𝑒 iii. Example: c. Gamma Emission i. Gamma is a high ________________ electromagnetic wave ii. Is emitted in _____________decay processes 1. Also known as gamma radiation = _______________ 6 Half Life 1. The half-life of an element is the time it takes for _____________ of the quantity of that element to _________________. a. The _________________ of the element remaining is _____________________ after each successive half-life is reached. b. Ex. The half-life of 146C is 5,730 years. If you start with 100.00 grams of 146C, after 17,190 years how much of 146C is left? Mass Left Years Passed Half lives 2. Carbon dating: a. While an organism is alive it is constantly replacing the carbon in its body with _________________ obtained from the food it ate or absorbed. b. While alive the ratio of Carbon-12 to Carbon-14 stays essentially _______________________. i. When dead the Carbon-14 in organisms begins to undergo ____________decay. ii. By measuring the amount of _________________ left, in dead organisms we can calculate how much ________________ has elapsed since the organism died. 7 Rutherford and Bohr Models 1. Ernest __________________ a. Conducted _____________ foil experiment in 1911 i. Shot __________ particles at a sheet of gold ___________ surrounded by a fluorescent screen. ii. Expected the alpha particles to go straight ___________________ the atoms based on J.J Thompsons plump pudding model of the atom. Rutherford’s Gold Foil Experiment iii. Concluded from the experiment that ____________ are mostly_________________ space and with a ____________ charged core , the _____________________. b. Nuclear Model i. Nucleus containing _______________and _______________ ii. Surrounded by mostly empty space containing _______________. iii. The atom is mostly empty space with a center ______________and ___________________that are in _______________ in the outer part of an atom. iv. When two atoms come near each other, it is the __________________ that interact. Rutherford’s Nuclear Model of the Atom 8 2. Niels________________ a. Proposed that electrons must have enough _______________ to keep them in ___________________motion around the nucleus. b. Electrons orbit the nucleus in orbitals of a _______________energy i. _____________________ can only circle the nucleus at certain _______________away from the nucleus; these are called _____________ or energy levels. Bohr’s Planetary Model of the atom 1. Each __________________has a certain amount of _____________________associated with it. a. Closer to the nucleus = a____________ orbit = ______________ energy b. Further away from the _______________= a _________orbit = ______________energy 2. ________________- the amount of energy needed to ________________to a new energy level. a. Electrons cannot be _______________ levels b. Proposed by Max ________________ How to find the number of valence electrons: The Bhor model of the atom: To draw the Bohr model of the atom: example: Ne 1. Start by placing the correct number of protons and neutrons of the element in the center a. Protons are found from the atomic number. b. Neutrons are found from subtracting the atomic number from the mass number of the most stable isotope. 2. Add enough energy levels for the element in question a. You can figure this out by counting the number of rows on the periodic table. b. Each energy level has a specific number of electrons that can go into it. i. First = 2 electrons ii. Second = 8 electrons iii. Third = 18 electrons iv. Fourth = 32 Electrons You try: O S K 9 3. _______________ _______________ Model – ____________ of ____________ based on the ______________ properties of an ___________________ a. Deals with the ___________________ of finding an _____________ orbiting an ________ b. ________________ i. _____________ region around the _______________ where an ___________can be found ii. Forms a __________around the _________________ iii. _____________and _____________ of the cloud depends on the ___________ ___________ of the ____________ iv. _______________ can exist _______________ in the ____________, but ________between orbitals. 4. Atomic Orbitals/ Quantum Numbers a. Ewin _______________ developed an _______________that describes the________________ of finding the position of an ___________________. b. Describes the _______________ of an ________________ in an _____________ i. ___________________Quantum Number (______) 1. The _________ ______________ the _____________ occupies 2. ______________ numbers ____________ 3. The ______________ the number is, the _______________ the _________ is away from the_________________ 4. ___________ is the ______________ number of_____________ in the __________ ____________ 5. Contains _____________ equal to _______ ii. ____________ Quantum Number (_______) 1. The _______________ of________ 2. Defines the ____________of the ____________ 3. _________is an _______________ from _______________ 4. Example- if n = 3 what are all possibilities for 𝓵 5. Each _____________ is expressed as a ____________ s,p,d,f 𝓵 = 0 (_______) Picture of s a. _________sublevel b. _____________ 𝓵=1 (_____) a. ______ sublevels Pictures of p b. ______________ 𝓵 =2 (_______) a. __________ sublevels 6. 𝓵 = 3 (______________) a. ______________sublevels 10 5. Electromagnetic Spectrum a. Total ________________ of ______________________ radiation 10 24 10 22 20 10 rays -16 -14 10 10 10-12 Wavelength (m) 10 18 10 rays 10-10 16 10 14 rays 10-8 10 12 IR 10-6 400 nm 10-4 10 8 6 10 10 10 Microwaves Radio Waves 10-2 100 10-2 Frequency (Hz) 10 102 100 Long Radio Waves 104 106 108 4 700nm vi. Wavelength (______) – Distance __________ corresponding _________ on adjacent waves vii. Frequency (__________) – ___________of ________ that pass by a point in a certain _____________ of time. 6. ________________ can be described as _____________or _____________ a. ______________states – when____________ are boosted to ___________ energy levels b. _____________________state – the _____________ energy level c. When _____________ go to a ________________ energy state they __________ a _______________ of energy. viii. This _____________ is in the form of ______________, called a ____________. 7. _____________ Uncertainty Principle a. _____________Physicist b. Determined it’s ___________ possible to measure both _____________and the ___________of an ______________ at the same ___________. 8. Bright light emission spectrum. a. Certain ____________ levels emit certain___________ when an __________ falls from them. b. Each ____________ has a particular ____________ associated with it and so emit a specific _____________ of _______________. 11 1. Electron configurations a. Written notation to show how _____________ are distributed within ________________ 1s2 b. Examples: i. Nitrogen ii. Potassium c. Exceptions: i. Cr ii. Cu d. Nobel Gas configurations: i. Potassium ii. Bromine e. Rules for orbital diagrams: i. Aufbau Principle –_______________ must occupy the _____________energy level ______________. ii. Hund’s Rule - Orbital's of ____________energy will occupy an _________ ______________ before ___________________ occurs. iii. Pauli ______________Principle – no two ______________ can have all _________quantum numbers the ______________. 12 How did you organize your candy? 1. History of the periodic table a. Demitriy ________________ i. Realized that the ________________ and _________________properties of the ______________________ repeated in an __________________ way when he organized the elements according to increasing _______________ ___________. ii. Elements with ________________properties were placed in the ____________ horizontal _____________. iii. Table showed that ____________________ of elements ____________ in an __________________way from row to row. iv. Mendeleev’s table left some ________________ spaces; this suggested that there were___________________ that had not yet been _________________. v. Using the table Mendeleev could ______________ the properties of these unknown elements. Properties of Eka- Aluminum (Germanium) Property Predicted (1869) Atomic mass 72 amu Color Dark gray Density 5.5 g/ml Melting point Very high Formula of oxide EsO2 Density of oxide 4.7 g/ml Oxide solubility in HCl Slight Formula of chloride EsCl4 Actual (1886) Gray-white 5.32 g/ml 937 0C GeO2 4.70 g/ml none GeCl4 13 b. ______________________- tendency to ___________at regular ______________. i. Mendeleev was so confident in ________________ that he placed some elements in groups with others of _______________ properties even though this __________________ did not go strictly by _____________ ____________. c. Henry _________________ i. Organized his ______________table by _____________ _______________. 2. Modern Periodic Table a. __________________ Law –_______________ and _________________ properties of elements _______________ in a regular _______________ when they are arranged by _______________ atomic number. 3 Undiscovered Elements 1. 2. 3. 8. Family Characteristics a) Group 1 (Alkali metals) i) Soft and highly reactive. ii) Alkali (1) Produce alkaline (basic) solutions (2) Slippery to the touch iii) Metal (1) Malleable (3) Conducts heat and electricity (2) Ductile (4) Luster iv) Have 1 electron in highest energy level. b) Group 2 (Alkaline earth metals) i) Harder and more dense than alkali metals. 14 ii) Not as reactive as alkali metals. iii) Contain 2 electrons in their highest energy level. c) Group 3 - 12 (Transition elements) i) All are metals. ii) Not as reactive as alkali or alkaline earth metals. iii) Electron configuration can change within a group in order to better stabilize the atom. d) Lanthanide Series – 71Lu i) 58Ce ii) Rare earth elements. iii) Most are radioactive e) Actinide series i) ii) 90Th – 103Lr All are radioactive. iii) Have unstable electron configurations. f) Group 13 – 18 (Main block elements) i) Represent a wide range of chemical and physical properties. ii) Contain metals, metalloids, non-metals and noble gases. g) Group 17 (Halogens – salt formers) i) Readily combine with alkali metals or alkaline earth metals to form a “salt” ii) Most reactive non-metals. iii) Have 7 electrons in the highest energy level. h) Group 18 (Noble Gases) i) The group of Noble gases were originally proposed by Strutt and Ramsey when they discovered the element Argon. ii) Have a full s and p orbitals iii) Stable configuration, or, resists change (inert). i) Hydrogen (Own family) i) Behaves like no other element. ii) Has only one electron. iii) Rare on earth in its free state, usually found in combination with other atom(s). (1) Ex. H2O, CH3CH2OH, CH3CH2CH2CH2CH2CH2CH2CH3 15 8. Octet Rule- in order for an element to be _____________ it must possess full ____ and ______orbitals a. Have _________ electrons in its _______________energy level! b. Elements will react _________________, or nuclearly to achieve this ________. Periodic Trends 1. Atomic Radius- ____________ of an ________________ a. _________________of the distance between the ________________ of _______________elements i. Diatomic ________________- elements that e_________ in nature as a ______________ 1. _____________ diatomic elements a. b. _______________ down a group i. The more _____________ ______________ there are the _____________ the atom is. c. _______________________ from left to right across a period i. ________________ effect- ________________ of the attraction between a __________________and its ____________ electrons due to the ______________ effect of the ______________electrons. 2. Ionization Energy a. ___________- an atom that has ____________ or _____________electron(s) giving it a __________________ i. ______________- an ion that has _______________ electron(s) 1. Have a _________________charge 16 ii. _______________- an ion that has ____________ electron(s) 1. Have a _________________charge b.________________ electrons- electrons in the ___________________energy _________of an atom. i. Responsible for _______________of the chemical ______________ between atoms ii. Electrons _______________ or _________________will be ______________ electrons How to find the number of valence electrons: The Bhor model of the atom: To draw the bohr model of the atom: example: Ne 3. Start by placing the correct number of protons and neutrons of the element in the center a. Protons are found from the atomic number. b. Neutrons are found from subtracting the atomic number from the mass number of the most stable isotope. 4. Add enough energy levels for the element in question a. You can figure this out by counting the number of rows on the periodic table. 5. Figure out how many electrons can go in each energy level. a. 2n2 rule 6. Add as many electrons as are in the element filling the energy levels starting closest to the nucleus. a. The number of electrons is equal to the number of protons. 17 b. ________________ energy- energy required to __________________an ________________from an element. i. ________________ down a _________________ 1. ________________ that are held more tightly to the__________ will be _______________________ to remove a. The _________________ an atom is the __________ energy required to______________an _____________. ii. _______________ from left to right in a ________________ a. The _________________an atom is the ___________energy required to ___________an electron. 3. ______________________- the tendency of an ___________________ to attract __________________ to itself when forming a ______________________. a. The higher the__________________, the more likely an ___________ is to attract ______________. i. _________ has the highest at _________________ b. ________________ down a _________________ i. The _____________________ the ________________ are held by the ______________, the greater the ____________________ is. ii. As the_____________ gets _____________ the__________________ gets ______________________. c. _______________________ from left to right in a _______________. i. As the atomic_______________ gets________________ the ____________________gets ___________________. 18 Martian Periodic Table +1 0 1 +2 +3 +4 -3 -2 -1 2 3 4 5 Element List A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # + * $ 19