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Physical Science A study of chemistry and physics -Understanding and Drawing Atoms Ions and Isotopes Why is the overall charge of an atom neutral? The atom has the same number of positive charges (protons) as negative changes (electrons). # protons = # electrons # of positive charges = # of negative charges NO CHARGE ! How do we know how many protons and electrons are in each atom? Look at the periodic table! Atomic Number All atoms of the same element have the same number of protons in the nucleus 13 Al 26.981 Atomic number Element symbol AVERAGE Atomic Mass Atomic Number the number of protons in the nucleus of an atom. The number of protons in the nucleus determines what the element is. The atomic number will never change. Since the atom has no charge……we can tell how many electrons the atom has by the atomic number. It has to be the same! Atomic Number Element # of protons Atomic # Carbon 6 6 Phosphorus 15 15 Gold 79 79 Mass Number and Atomic Mass Mass Number = the sum of the protons and neutrons in an atom’s nucleus. Atomic Mass = the average mass of all isotopes of that element as they occur in nature. Drawing Atoms Determine the # of protons Determine the # of electrons Look at the Atomic Number F Will be the same as the # of protons Determine the # of neutrons 9 18.998 Mass number – atomic # = # of neutrons (Round the atomic mass number to nearest whole number , 18.998 rounds to 19) 19 – 9 = 10 neutrons Determine the placement of electrons in the energy levels Level 1- holds no more than 2 Level 2- holds no more than 8 Level 3- holds no more than 18 Mass Number Mass number is the number of protons and neutrons in the nucleus of an isotope: Mass # = p+ + n0 p+ n0 e- Mass # 8 10 8 18 Arsenic - 75 33 42 33 75 Phosphorus - 31 15 16 15 31 Oxygen - 18 Chemical Symbols First letter of element’s name S Sulfur, O Oxygen, N Nitrogen First two letters of element’s name Ca First and third of later letter of element’s name Mg Calcium, Ne Neon, He Helium Magnesium, Mn Manganese Cl Chlorine First letter or letters of name in Latin Fe Iron (ferrum), Pb Lead (plumbum) Fluorine Atom Protons = 9 Neutrons = 10 Electrons = 9 Level 1= 2 Level 2 = 7 Isotopes Atoms of the same element must have the same number of protons but can have a different number of neutrons. These atoms are known as isotopes. Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons. Isotope Protons Electrons Neutrons Hydrogen–1 (protium) 1 1 0 Hydrogen-2 (deuterium) 1 1 1 1 1 2 Hydrogen-3 (tritium) Nucleus Isotopes Elements occur in nature as mixtures of isotopes. Isotopes are atoms of the same element that differ in the number of neutrons. Atomic Mass How heavy is an atom of oxygen? It depends, because there are different kinds of oxygen atoms. We are more concerned with the average atomic mass. This is based on the abundance (percentage) of each variety of that element in nature. We don’t use grams for this mass because the numbers would be too small. To calculate the average: Multiply the atomic mass of each isotope by it’s abundance (expressed as a decimal), then add the results. If not told otherwise, the mass of the isotope is expressed in atomic mass units (amu) Atomic Masses Atomic mass is the average of all the naturally occurring isotopes of that element. Isotope Symbol Carbon-12 12C Carbon-13 13C Carbon-14 14C Composition of the nucleus 6 protons 6 neutrons 6 protons 7 neutrons 6 protons 8 neutrons Carbon = 12.011 % in nature 98.89% 1.11% <0.01% Atomic Symbols Show the name of the element, a hyphen, and the mass number in hyphen notation sodium-23 Show the mass number and atomic number in nuclear symbol form mass number 23 11 atomic number Na Complete Symbols Contain the symbol of the element, the mass number and the atomic number. Mass Superscript → number Subscript → Atomic number X Symbols Find each of these: a) number of protons b) number of neutrons c) number of electrons d) Atomic number e) Mass Number 80 35 Br Symbols If an element has an atomic number of 34 and a mass number of 78, what is the: a) number of protons b) number of neutrons c) number of electrons d) complete symbol Symbols If an element has 91 protons and 140 neutrons what is the a) Atomic number b) Mass number c) number of electrons d) complete symbol Symbols If an element has 78 electrons and 117 neutrons what is the a) Atomic number b) Mass number c) number of protons d) complete symbol Isotopes? Which of the following represent isotopes of the same element? Which element? 234 92 X 234 93 X 235 92 238 X 92 X Learning Check – Counting Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #p+ _______ _______ _______ #no _______ _______ _______ #e- _______ _______ _______ Learning Check An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 3) 34 C. The element is 1) Si 2) Ca 3) Se D. Another isotope of this element is 1) 34X 16 2) 34X 14 3) 36X 14 Isotope lab Beans = proton Corn = neutron Atoms vs Ions Since the number of electrons = the number of protons the overall charge of an atom is neutral. If an atom should lose or gain an electron it is not longer an atom but a charged particle called an ion. if atom loses an electron, a POSITIVE ion is created If atom gains an electron, a NEGATIVE ion is created IONS IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge. To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2 Na Ca I O Forming Cations & Anions A CATION forms when an atom loses one or more electrons. Mg --> Mg2+ + 2 e- An ANION forms when an atom gains one or more electrons F + e- --> F- PREDICTING ION CHARGES In general metals (Mg) nonmetals lose electrons ---> (F) cations gain electrons ---> anions Learning Check – Counting State the number of protons, neutrons, and electrons in each of these ions. 39 K+ 16O -2 41Ca +2 19 8 20 #p+ ______ ______ _______ #no ______ ______ _______ #e- ______ ______ _______ One Last Learning Check Write the nuclear symbol form for the following atoms or ions: A. 8 p+, 8 n, 10 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 46 e- ___________ The Atoms Family Album In the center of Matterville there is a place called the Nucleus Arcade where two member of the Atoms Family like to hang out. Perky Patty Proton, like her sisters, is quite large with a huge smile and eyes that sparkle (+). Patty always has a positive personality. The Atoms Family Album Nerdy Nelda Neutron is large like Patty, but she has a boring, flat personality and her eyes have zero expression (0). Her family is very apathetic and neutral about every thing. Patty, Nelda, and their sisters spend all of their time at the arcade. The Atoms Family Album Around the Nucleus Arcade you will find a series of roadways that are used by another member of the Atoms family, Enraged Elliot Electron. Elliot races madly around the Arcade on his bright red chrome-plated Harley-Davidson. He rides so fast that no one can be sure where he is at any time. Elliott is much smaller than Patty and Nelda and he is always angry because these bigger relatives will not let him in the Arcade. He has a frown on his face, eyes that are squinted with anger, and has a negative (-) attitude. The Atoms Family Album The first energy street can only hold _____ electron brothers. The second energy street, called the Energy Freeway, can only hold___ brothers. The third energy street, called the Energy Superhighway, can hold ____of the brothers. The Atoms Family Album The morale of Matterville is stable as long as each negative Electron brother is balanced out by one _______ proton sister. The number of residents in Matterville depends on the Proton and Neutron families. Challenge: What would happen to the morale of Matterville if one Elliott Electron was kidnapped? The Atoms Family Song They’re tiny and they’re teeny, Much smaller than a beany, They never can be seeny, The Atoms Family Chorus: They are so small (snap, snap) They’re round like a ball (snap, snap) They make up the air, They’re everywhere, Can’t see them at all. (snap, snap). The Atoms Family Song Protons with a positive charge, Neutral neutrons rather large, Negative electrons really are The Atoms Family. Chorus: They are so small (snap, snap) They’re round like a ball (snap, snap) They make up the air, They’re everywhere, Can’t see them at all. (snap, snap). The Atoms Family Song Protons, neutrons are inside, In the nucleus they abide, While electrons race outside. The Atoms Family. Chorus: They are so small (snap, snap) They’re round like a ball (snap, snap) They make up the air, They’re everywhere, Can’t see them at all. (snap, snap). The Atoms Family Song Together they make gases, And liquids like molasses, And all the solid masses, The Atoms Family! Chorus: They are so small (snap, snap) They’re round like a ball (snap, snap) They make up the air, They’re everywhere, Can’t see them at all. (snap, snap).