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Arnoldi Chemistry Atomic Theory One Note Sheet Answer Key I. Atomic Theory Background Information A. What is an atom? 1. Atoms are the _________________________ of matter. 2. An atom is the _________________________ that still retains the properties of that element. B. Important Definitions 1. _______________ (Z): # of protons in the nucleus a. The atomic number is the _____ number on the periodic table. (the PT is arranged by atomic number) b. The atomic number controls the _________________. (the identity of the atom is based on the number of protons in the atom) 2. ___________: a. the sum of the protons and neutrons in the nucleus This is the mass for _________________. b. Mass Number is ______ on the Periodic Table. 3. Subatomic Particles: a. Atoms are made up of ________________________. b. Table Particle Charge Mass (Two Ways) Location in Atom Proton + 1 amu # In Nucleus Electron - Negligible *Outside of Nucleus Neutron neutral 1 amu # In Nucleus # Nucleons: (____________ and _____________) * Electrons are actually found in _______________. What is the nucleus? The nucleus is the small, dense, positively charged __________________. 4. ________ a. atoms with a charge / charged particles _____________ control the charge of the particle. When the number of protons and electrons in the atom is the same, the atom is _____________. When the number of protons and electrons in the atom is ______________, an ion exists. Since protons cannot be changed without changing the identity of the atom, it is electrons that are ________ or ____________ when forming ions. b. ___________: negatively charged particles Anions are formed when electrons are ________. c. ___________: positively charged particles Cations are formed when electrons are ________. 5. _________: atoms of the same element with different masses Remember, only protons and neutrons have significant mass. Since protons cannot be changed without changing the identity of the atom, isotopes occur when atoms of the same element have different numbers of neutrons. a. An Example: The Three Hydrogen Isotopes Hydrogen Protium Deuterium Tritium (artificial Isotopes and radioactive) Protons 1 1 1 Neutrons 0 1 2 Electrons 1 1 1 Mass 1 amu 2 amu 3 amu % Abundance 99.85% .15% 0% b. How do we write an isotope? 12 Carbon – 12 C 6 12 or C Carbon / C is the identity of the element. ___ is the mass number. ___ is the atomic number. d. How do we determine protons, electrons and neutrons? look on the _________ Protons = Atomic Number Electrons = protons if the atom is _______________. If the atom is charged… Positive ions have _____ electrons than protons. Negative ions have _____ electrons than protons. Neutrons = Isotope Protons Electrons Neutrons 40 +1 K 12 14 C S-2 12 38 36 53 9 10 10 PROMPT ONE Use this table to answer the following questions: Particle Protons X 17 Y 17 Electrons 17 17 Neutrons 18 19 (a) Explain why these two particles are the same element. (sentences, s/g) (b) Explain why these two particles are called isotopes. (sentences, s/g) (c) What is the mass number of particle X? Explain how you determined this answer. (sentences, s/g) PROMPT TWO Use this table to answer the following questions: Particle Protons X 17 Y 17 Electrons 17 18 (a) Write the isotope/ion designation for each of the particles. (b) Explain why the Y particle is called an ion. (sentences, s/g) Neutrons 18 19 6. __________: a. the average mass of the isotopes of an element aka Classroom Height Example b. Equation Average atomic mass = EXAMPLES: [(% abundance)(mass of 1st isotope)] + [(% abundance)(mass of 2nd isotope)]...... 100 What is the atomic mass for element B? 11 B = 80.20% 10 B = 19.80% PROMPT THREE Given the following information, what is the average atomic mass of neon (to five decimal places)? Isotope Exact Mass (amu) Percent Abundance Neon – 20 Neon – 21 Neon – 22 19.99244 20.99395 21.99138 90.51 .27 9.22 II. Early Atomic Theories A. Democritus: 1. 460 BC, Greek 2. First person to use the term “______”, which means ________. 3. He also thought atoms were ______ and ______________. 4. There is _______________________ to support his ideas. B. John Dalton 1. English, 1803 2. Dalton’s Main Ideas About Atomic Theory a. All matter is made up of _______ which are _________ and ___________. b. Atoms of the same element are _________________ – in particular their _________ are the same. Atoms of different elements are _____________ different, in particular their _____________ are different. c. Atoms combine in _________________________ (by mass) to form compounds. 3. Billiard Ball Model 4. What part of Dalton’s theory do we still believe? a. Matter ________ made of atoms. b. Atoms ______________ in simple whole number ratios. c. Chemical rxns _________________ of the separating / combining of atoms. 5. What part of Dalton’s theory do we not believe? a. Atoms are ___________. They can be divided into subatomic particles, (protons, electrons and neutrons). b. Atoms are ___________ in nuclear reactions (we can create atoms in nuclear reactions, also). b. Atoms of different elements ___________________, and ______________________ can have different masses. This occurs because of isotopes. 12 C vs. 13C 14 C vs. 14 N PROMPT FOUR Write three important contributions towards atomic theory for each of the following: (a) Democritus (b) John Dalton III. Developing Atomic Theories A. J J Thomson 1. 1890s, English 2. Used Crookes’ (another scientist) Tube to discover the electron. 3. Diagram: X 4. Explanation J J Thomson took a cathode ray tube and applied a magnetic field. When a negative field was introduced, the cathode ray was ___________________. When a positive field was introduced, the cathode ray was _______________. From this, Thomson concluded that the cathode ray was composed of a stream of _______________________, which he called ________________. 5. Model – Plum Pudding C. Rutherford 1. 1911, New Zealand 2. Rutherford used the ____________________ to discover evidence for a nucleus. 3. Diagram Alpha Particles a few were deflected Gold Foil most go through 5. Description Rutherford bombarded gold foil with ________________. Most of the particles __________________. A few were ___________. Since alpha particles are ____________ and they were deflected, not attracted, they must have hit something positive inside of the atom (likes repel). Rutherford concluded that there is a _______________________ center in the atom, which he called the ____________. The rest of the atom is ______________________. Analogy: if an atom is the size of the Eagle’s stadium, then the nucleus is the size of a tennis ball floating in the middle of the stadium. 6. So, where are the electrons? The electrons are somewhere ____________________ occupying most of the volume of the atom. *If electrons are negative, and the center of the atom is positive, why aren’t they attracted to the center of the atom? 7. Model PROMPT FIVE Write three important contributions towards atomic theory for each of the following: (a) Thomson (b) Rutherford D. Niels Bohr 1. Bohr began to explain the location of electrons as accepted today. This is a _____________________ of what is really happening. 2. Electrons reside in __________________, aka energy shells. 3. The energy of the electron shell and the distance of the shell from the nucleus are __________________. (The energy of the level ___________________ as the distance from the nucleus increases). 4. Electrons fill the energy levels from the ____________, which means the first energy shell is filled before electrons enter the second shell, the second energy level is filled before electrons enter the third shell, etc. This means that electrons fill shells ________________. 4. Bohr Diagrams give us a quick look at how the electrons are arranged. a. Basic Pattern # of Protons shows the _________ number of electrons allowed in the energy levels )2e- )8e- b. Examples (i). Sodium Atom (ii). Sodium Ion (+1) (iii). Chlorine Atom (iv). Chlorine Ion (-1) )8e- 5. Ground vs. Excited States a. An atom occupies the _______ state if it is in the _______ possible energy state. This occurs if the first shell is filled before electrons are placed in the second shell, the second shell is filled before electrons are placed in the third shell, etc. b. An atom is considered to be in the _________ state if it is ______ in the lowest possible energy state. This occurs if one of the inner shells is not completely filled before moving to the next shell. c. The ground state is also called the _________ state. The excited state is also called the _________ state. 6. To move from one energy level to another, you must _________ __________ amount of energy between those two levels. PROMPT SIX Explain why each of the following Bohr diagrams is correct or incorrect. Potassium Atom Oxygen Ion (-2) 19p ) 2e- )8e- )8e- )1e- 8p )2e- )4e- 11 p )8e- )2e- Sodium Ion (+1) E. Comparing Modern Atomic Theory to Dalton’s Atomic Theory 1. Similarities matter _____ composed of atoms atoms ___ combine in simple whole number ratios 2. Differences atoms are divisible (_________________) atoms are destructible (______________) atoms of the same element sometimes have different masses and atoms of different elements sometimes have the same mass (___________) Electrons are in a region of high probability called an _____. They are not in an exact shell location. IV. What experimentation led us to understand the location of electrons? A. Spectroscopy B. Some Important Definitions 1. All of the frequencies and wavelengths of electromagnetic radiation. 2. The uninterrupted broad band of all colors (one color blends into the next). 3. The spectrum where distinct lines of color appear. Each color corresponds to distinct _________________. The can be used like a _______________ for the element.