NOTES Name: Date: Class: Lesson 12: Atoms and Subatomic Particles Element: fundamental substance that ; all matter consists of ~100 elements Atom: that can exist; smallest unit of an element that can enter into a chemical reaction Atoms are comprised of 3 SUBATOMIC PARTICLES: 1. Proton. Located in the of an atom. Defines the atom. Has a charge of and a mass of. 2. Neutron. Located in the of an atom. Stabilizes the positively-charged nucleus. Has a charge of and a mass of. 3. Electron. Located in the of an atom. Participates in. Has a charge of and a mass of. Atoms are drawn/represented in several ways, but there are usually flaws with each image. The figure on the left is a classic Bohr model representing electron shells as circles. The figure on the right is a more accurate representation of the atom. Nucleus Electrons www.chemistrywithdrjames.com 1
The nucleus contains.. It s the small center of an atom and has a. The electron cloud is and is composed of. Electrons travel around the nucleus in groups called. New unit for mass:. Because subatomic particles are SO SMALL, it doesn t really make sense to use kilograms or grams as the mass unit. Instead, we use which stands for atomic mass unit. The Dalton (Da) and unified atomic mass unit (u) are equivalent to the amu. If you re interested http://physics.bu.edu/~duffy/sc546_notes10/mass_defect.html The mass of an electron is actually 0.00055 amu. It would take about 1800 electrons to equal the mass of one proton https://cnx.org/contents/rtmuixzm@7.234:uxg0kua-@4/introduction www.chemistrywithdrjames.com 2
Counting Subatomic Particles: PROTONS The in the nucleus of an atom as a particular element. Any and all atoms of Chlorine will have protons, regardless of how many neutrons and electrons it has. The number of protons in the nucleus of each element is expressed as its (denoted as Z ). The atomic number is found on the Periodic table. Given the number of protons, identify the element: 1. 14 protons = 4. 27 protons = 2. 28 protons = 5. 79 protons = 3. 44 protons = 6. 100 protons = Given the element, write the number of protons: 1. Chlorine = 4. Te = 2. Molybdenium = 5. At = 3. Barium = 6. Pm = Draw your own diagram of a complete atom: www.chemistrywithdrjames.com 3
NEUTRONS Atoms of the same element that have different numbers of neutrons are called. Naturally occurring elements exist as a of isotopes. These are of the same element. Naturally Occurring Isotopes of Chlorine Chlorine-35 (most abundant) protons + neutrons. 24% 76% Chlorine-35 Chorine-37 Chlorine-37: protons + neutrons. We express the number of neutrons as the. The mass number is the total number of AND. It s not listed directly on the Periodic Table. Ways the mass number is written: 1. Hyphen notation: Oxygen-16 2. Nuclear notation: 16 O or 8 16 O www.chemistrywithdrjames.com 4
Complete the table: Isotope Hydrogen - 1 Hydrogen - 2 Hydrogen - 3 Helium - 3 Helium - 4 Uranium - 235 Strontium - 87 Tungsten - 184 Nuclear Symbol 1 1 H 2 1 H 3 1 H 3 2 He 4 2 He 235 92 U 87 38 Sr 184 74 W # of Protons # of neutrons 33 42 26 30 53 74 ELECTRONS: Since each proton as a charge and each electron has a charge, an atom with the same number of electrons as protons is considered neutral with an overall charge of. For example, a neutral atom of Sodium has protons and electrons. Electrons are often as atoms. During, atoms sometimes lose or gain electrons to form. Atom loses electron(s) = Atom gains electron(s) = Ions are represented in the nuclear notation. www.chemistrywithdrjames.com 5
Element Neutral element: # of protons and electrons Ion formation Ion: # of protons and electrons Symbol to represent ion Lithium Neutral Li: Lithium loses 1 electron Lithium ion: Oxygen Neutral O: Oxygen gains 2 electrons Oxygen ion: Calcium Neutral Ca: Calcium loses 2 electrons Calcium ion: Chlorine Neutral Cl: Chlorine gains 1 electron Chlorine ion: Ways to represent ions and isotopes: www.chemistrywithdrjames.com 6
REVIEW: Subatomic particle Charge Mass Mass number Location Neutron Proton Electron ELECTRON CONFIGURATION: Electrons orbit the nucleus in groups called. In the Bohr model, shells are represented as circles around the nucleus. Electrons orbit at various distances from the nucleus. are electrons that exist in the electron shell. All electrons are considered to be By looking at the figures above, how many electrons of each type does each atom have? Nitrogen has valence electrons and core electrons. Oxygen has valence electrons and core electrons. Fluorine has valence electrons and core electrons. Valence electrons are the electrons and participate in and. www.chemistrywithdrjames.com 7
The number of valence electrons that a neutral atom has can be determined by looking at the Periodic Table. Group/Column #: # of valence e s: Total # of electrons Valence electrons = # of core electrons Neutral Element Li Cl Sb Si F Mg S # of Protons (atomic number) Total electrons Valence electrons Core electrons www.chemistrywithdrjames.com 8
This is a(n) neutral atom / ion of. It has total electrons, valence electrons and core electrons. This is a(n) neutral atom / ion of. It has total electrons, valence electrons and core electrons. This is a(n) neutral atom / ion of. It has total electrons, valence electrons and core electrons. Review Questions: 1. In what way are isotopes of a given element always different? In what way(s) are they always the same? 2. Write the symbol for each of the following ions: a. the ion with a 1+ charge, atomic number 55, and mass number 133 b. the ion with 54 electrons, 53 protons, and 74 neutrons c. the ion with atomic number 15, mass number 31, and a 3 charge d. the ion with 24 electrons, 30 neutrons, and a 3+ charge www.chemistrywithdrjames.com 9
3. Open the Build an Atom simulation (http://openstaxcollege.org/l/16phetatombld) and click on the Atom icon. a. Pick any one of the first 10 elements that you would like to build and state its symbol. b. Drag protons, neutrons, and electrons onto the atom template to make an atom of your element. State the numbers of protons, neutrons, and electrons in your atom, as well as the net charge and mass number. c. Click on Net Charge and Mass Number, check your answers to (b), and correct, if needed. d. Predict whether your atom will be stable or unstable. State your reasoning. e. Check the Stable/Unstable box. Was your answer to (d) correct? If not, first predict what you can do to make a stable atom of your element, and then do it and see if it works. Explain your reasoning. 4. Give the number of protons, electrons, and neutrons in each of the following isotopes: a. 10 5 B b. 199 80 Hg c. 63 29 Cu d. 13 6 C e. 77 34 Se Vocabulary: anion: negatively charged atom or molecule (contains more electrons than protons) atomic mass: average mass of atoms of an element, expressed in amu atomic number (Z): number of protons in the nucleus of an atom cation: positively charged atom or molecule (contains fewer electrons than protons) electron: negatively charged, subatomic particle of relatively low mass located outside the nucleus ion: electrically charged atom or molecule (contains unequal numbers of protons and electrons) isotopes: atoms that contain the same number of protons but different numbers of neutrons mass number: sum of the numbers of neutrons and protons in the nucleus of an atom neutron: uncharged, subatomic particle located in the nucleus nucleus: massive, positively charged center of an atom made up of protons and neutrons proton: positively charged, subatomic particle located in the nucleus unified atomic mass unit (u): alternative unit equivalent to the atomic mass unit www.chemistrywithdrjames.com 10