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M7 THE ATOM Foundational Research Package II A CLOSER LOOK AT THE STRUCTURE OF MATTER December 2007 - Team E Science ANSWERS TABLE OF CONTENTS Introduction, Objectives and Study Guide………..1 Research and Practice Properties of Atoms…………………………..2-6 The Bohr Model Revisited..…………………...7-8 The Periodic Table……………………………9-14 We have just concluded our intro to the heart of the matter. From this experience, we were able to discover: 1) 2) 3) 4) the the the the classes of matter. history of the atom. structure of the atom. forces of the atom. We are now going to get deeper into the heart of the matter with a look at the following questions and concepts. PROBLEM 1: How do we distinguish between the atoms of different elements? THE FIVE PROPERTIES OF ATOMS Chemical Symbol Chemical Name Atomic Mass Atomic Number Mass Number (and Isotopes) PROBLEM 2: How do we illustrate the structure of the atom? THE BOHR MODEL Determination of number of subparticles Placement of subparticles Predicting bonding PROBLEM 3: How do we organize the elements for studying purposes? THE PERIODIC TABLE Periods/Rows vs. Columns Meaning of column #’s Families: Non-metals, Metals, Metalliods, Inert/Noble Gases Now that you know what we’ve got to learn, let’s get a-learning…NOW! FYI – your quiz on these questions is planned for NEXT THURSDAY…December 20th! You will be asked to answer questions on ONE element. This packet, as well as your review packet (M-8), will be the materials you need to study for this quiz. PROBLEM #1 How do we distinguish between the atoms of different elements? A closer look at the properties (i.e. characteristics) of the atom In this section of our closer look at the atom, we will take a look at how we distinguish between the atoms of different elements. First, let’s define what a “property” is and why it is important in studying atoms. What is a “property” of an atom and why do we need to refer to these “properties” when we are talking about atoms? _______IT IS A CHARACTERISTIC OF AN ATOM THAT HELPS US TO ID WHAT ELEMENT IT IS _______________________________________________________________________________________ There are FIVE properties of atoms that you need to know about and understand. They are… Property Definition The first two properties, the chemical __NAME___ and Chemical __SYMBOL___, are the ways that we label or “call” or “name” atoms. Name and The symbol comes from the first letter or letters in the chemical’s Symbol ____ENGLISH_________ or ____LATIN__________ name. The third property, _ATOMIC_____ __NUMBER____, is equal to the number of protons OR electrons. It is the property that gives an Atomic Number atom the chemical characteristics that make it different from other atoms. Why? Because if you change the number of _p+_____ and __Ø_____ in an atom, you are changing its IDENTITY and all that makes it what it is (i.e. its ___PROPERTIES______) and what it can do with other atoms (i.e. __BOND!________). Location in an entry on Periodic Chart The fourth property, the ____ATOMIC_____ _____MASS______, tells us how much “matter” or ___MASS________ or a.m.u.’s there is/are in the _AVERAGE______atom of an element (i.e. the number of Atomic Mass _p+___ and __Ø__ ). Why is there an average mass? The mass of an element can be different from atom to atom of that element. This is because __# OF p+____can never change for a given atom, but __ Ø ______ can because they have a ___NEUTRAL____ charge and therefore will not change the atom’s identity but will change its ____MASS___. The fifth property, the _MASS_____ __NUMBER____, is the Mass Number ___ACTUAL______ mass of an __ACTUAL____ atom…not the _AVERAGE MASS___ from the periodic chart. Therefore, it is the __ACTUAL___ amount of __p+_____ and ___ Ø ____ in an _ACTUAL_ atom. This __ACTUAL__ sample of an element is called an _ISOTOPE_. AN ENTRY FROM THE PERIODIC TABLE… Identify the properties in this entry from the periodic table. __ATOMIC #____ _____CHEM SYMBOL___ 1 ____________________ H ___CHEM NAME________ ______ATOMIC MASS_______ Hydrogen 1 Now assume you are given an isotope for Hydrogen. We identify an isotope by writing its chemical name OR symbol followed by a dash and then its mass number. An example isotope of Hydrogen is Hydrogen-2 or H-2. How would this isotope of Hydrogen be different from the average atom that is listed on the Periodic Table? _ATOMIC #_______ _1_ ____IT WOULD HAVE 1 MORE Ø THAN THE AVERAGE ON THE H Hydrogen _2_ __MASS #______ PERIODIC TABLE__________________________________________________ _________________________________________________________________ Copper (Cu) Helium (He) Boron (B) Magnesium (Mg) Lead (Pb) Chemical Name Cu-60 He-3 B-11 Mg-28 Pb-207 Isotope (Actual Sample) 64 4 11 24 207 Atomic Mass 29 2 5 12 82 Atomic Number 60 3 11 28 207 Mass Number 29 4 5 12 82 Electrons 29 4 5 12 82 Protons 35 2 6 12 125 Average Neutrons 31 1 6 16 125 Isotope Neutrons 4 less than average 1 less than average Same as average 4 more than average Same as average Difference? PART I. PROPERTIES OF ATOMS PRACTICE PROBLEMS Below is a list of the properties of isotopes of five different elements. Use the information given to you, your notes on properties of atoms, and the periodic chart in your green folder to fill in the missing information. PART II. USES OF ISOTOPES So…what’s the big deal about isotopes? Why is it so important that there are atoms of the same element that have different amount of neutrons? To figure this out… Pick an isotope from the attached list. Read the information about your selected isotope. Grab your periodic table. Answer the following questions. 1) Pick one of the isotopes and write its name here:_________________________________ 2) How does the isotope you selected differ from the average atom that is shown on the periodic chart? Fill in the information below and then explain the difference(s) (if there is/are one/any!) in the space provided. THE PERIODIC CHART INFO: ISOTOPE INFO: Atomic # ____ ____ Chem. Sym. ____ Atomic Mass ____ Mass Number __________________________________________________________________________________________ __________________________________________________________________________________________ 3) Why is the isotope you selected important? In other words, what special property does it have and/or what do we use it for? __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ EXAMPLES OF ISOTOPES PROBLEM #2 How do we illustrate the structure of the atom? A FINAL and CLOSER look at the Bohr Model The Bohr Model is something that should be relatively familiar to you…but NOW is the time to really get a grip on it! WARNING! This might just be a little “Bohring” since you already know a bit about it! SO, hot-shot scientists, let’s see what you know by trying to fill out the important info about the Bohr Model in the space below… THE PURPOSE OF THE BOHR MODEL The purpose of the Bohr model is to: 1) _____Predict structure of atom_____________________________________________________________ 2) _____Predict bonding – valence shell “emptiness” predicts if atom will bond and how it will bond_______ THE PROCEDURE FOR MAKING A BOHR MODEL – this works for the first _____ elements ONLY! 1) Get a __PERIODIC_____ ____TABLE___!!! (or look at the info given about an isotope of an element) 2) Find the number of __p+__ in the atom by looking at the atomic __#________ for that atom. 3) Find the number of __e-____ in the atom by looking at the atomic __#______ again. This is same number as the number of _p+__ because atoms must be __NEUTRAL (i.e. no charge)_____. 4) Find the number of __ø____ by _____SUBTRACTING ___ the atomic __#______ FROM the atomic ___MASS________ (or mass ____#______ if an isotope). 5) Draw the ___NUCLEUS ____ as a circle. Put the ___CHEM_____ ___SYMBOL__ and the number of _____p+___ and ____ ø ___ in the circle. 6) Fill the __ENERGY__ ___LEVELS___ with the right number of __e-______ according to the pattern of _2__ - __8_ - __8_ ! Do ___NOT_____ fill a new ___ENERGY___ ____LEVEL__ until the level you are in is filled to its ___MAX__________ capacity! 7) Remember, for all subatomic particles it is necessary to put the ___#_______ before the __SYMBOL___ when listing the amount of the sub particles in the atom! LET’S DO SOME “BOHRING” PRACTICE! 1) Do the Bohr Model for an isotope of Aluminum 13 Al 26 Al 2 e- 8 e- 3e- 13 p+ 13 Ø Is this isotope of Aluminum different from the average isotope of Aluminum? Explain your answer. ____Yes – it has one less neutron than the average_______________________________________ 2) Do the Bohr Model for an isotope of Sulfur 16 S 32 S 16 p+ 16Ø 2 e- 8 e- 6e- Is this isotope of Sulfur different from the average isotope of Sulfur? Explain your answer. ______No, mass number =atomic mass__________________________________________________________ 3) Do the Bohr Model for an isotope of ????????????? 10 ? 20 Ne 10 p+ 10 Ø 2 e- 8e- What is the identity of the mystery isotope? Is this isotope different from an average isotope of that element? Explain your answer. ____Neon – no, has same amount of neutrons/atomic mass___________________________________ Will this atom bond with other atoms? Why or why not? ________No – has a full valence shell_____________________________________________ PROBLEM #3 How do organize the elements for studying purposes? A look at the “periodic pattern” in the Periodic Table DO NOW: An isotope of oxygen has a MASS NUMBER of 9. Find oxygen on your periodic table (oxygen is located in the 3rd to last column). Use the information in your periodic table and the MASS NUMBER of this atom of oxygen to: 1) DRAW the Bohr model for this isotope of oxygen. 2) LIST the number of subatomic particles in this isotope of oxygen. 3) LIST how many more or less neutrons this isotope of oxygen has compared with the “average” oxygen atom. Bohr Model: O 2e- 6e- e- p+ Ø Difference in neutrons 8 8 1 7 less 8 p+ 1Ø ONE MORE QUESTION: What could be the LOWEST possible MASS NUMBER for an isotope of oxygen? HIGHEST? Explain your answers! _________8 – because if you go lower than 8 you are taking away neutrons!____Highest…technically…infinity!__ __________________________________________________________________________________________ __________________________________________________________________________________________ INTRODUCTION TO THE PERIODIC TABLE… The Periodic Table A scientific problem. A periodic pattern to be discovered. Two detectives. One answer found and reformulated. Now, for the “rest” of the story… The Russian scientist Dmitri Medeleev was the first chemist responsible for “creating” the periodic chart of elements. Scientists during Dmitri’s time were trying to figure out an easy way in which they could organize the elements of matter so that it would be easy for them to communicate about their properties (i.e. scientists, even back then, were lazy and they didn’t want to have to memorize all the elements and their properties). Dmitri was, as are all scientists, a problem solver. His problem was to organize the elements into a predictable, easy to understand way…he want to predictably order or .“periodically arrange” the elements in a way that relate the elements properties to their placement in a table. To solve this problem – to organize the elements into a table that had a periodic or predictable pattern of element properties – Dmitri first made cards of all the known elements. On each card he wrote the element’s name and all of its properties (e.g. atomic mass, density, color, melting point, and ability to BOND with other elements). The ability to bond with other elements was expressed as VALENCE NUMBER. This was a number that reflected the number of electrons that the element would want to SHARE, LOSE, or GAIN when it combined with other elements. GET THAT? When atoms combine with one another, they either SHARE, LOSE, or GAIN electrons in their VALENCE SHELLS. The VALENCE NUMBER is the NUMBER of electrons that an atom will most likely LOSE, GAIN, or SHARE. This is different from the NUMBER of VALENCE ELECTRONS! The number of valence electrons is JUST how MANY electrons there are in the VALENCE SHELL…NOT how many the atom will most likely lose, gain, or share. As he was “playing cards,” Dmitri fell upon a pattern. By arranging them in order of atomic mass, he noticed that there was a pattern in the VALENCE NUMBER of the elements for EVERY SEVEN elements. The pattern was LOSE 1 e-, LOSE 2 e-, LOSE 3e-, GAIN OR LOSE 4e-, GAIN 3e-, GAIN 2e-, GAIN 1e-. Using this pattern as his guide and keeping to the order of increasing atomic mass, he then put the elements into columns instead of a long strand of elements: all the elements that would lose one electron were in column one, all the elements that would lose 2 electrons were in column two, etc. When he did this, he saw another pattern! The chart or table that he created was predictable and periodic according to atomic mass, valence number AND several other physical and chemical properties! The problem of creating a chart of the elements that reflected a predictable, periodic pattern of atomic properties had been solved…ALMOST! Some elements just didn’t seem to fit in to the pattern of increasing atomic mass and valence numbers. Science never stops, and the same holds true for the “creation” of the periodic table…50 years later a NEW atomic property – ATOMIC NUMBER (the number of protons and neutrons) – was discovered by another scientist: the Brit Henry Moseley. It was then that the pattern in the periodic table was truly founded…elements, instead of being ordered as a function of their atomic mass, were ordered as a function of their atomic number. The “periodic” pattern in the table of elements was based on ATOMIC NUMBER and VALENCE instead of ATOMIC MASS and VALENCE! …And, in the words of talk radio commentator Paul Harvey… “that’s the ‘rest’ of the story.” THE PROBLEM: HOW DO WE ORGANIZE THE ATOM FOR STUDYING PURPOSES? The answer… THE PERIODIC TABLE a.k.a. THE PERIODIC CHART a.k.a. THE TABLE OF ELEMENTS! NOTE: Thanks to those Russian and British dudes (Mendeleev and Moseley), the periodic table is arranged in a predictable…periodic …USEFUL way. It has a pattern to it…the properties of the elements are predictable according to their location…they repeat themselves periodically (hence the name “periodic” table). So...USE it to your ADVANTAGE! That’s why it’s there…that’s why it is arranged in the way that it is! YOU DON’T HAVE TO MEMORIZE THE ELEMENTS AND THEIR CHARACTERISTICS! By using the chart often, you will automatically become familiar with the elements and the characteristics! Here are some important periodic patterns in our most beauteous of all chemical charts. 1. The periodic table has ____PATTERN______________________. a) All the elements in EACH ____COLUMN____ have the same # of _VALENCE_ electrons (the same # of electrons in the _LAST___ energy level). The main columns of the periodic table can be labeled so that the column # is the same # as the # of __VALENCE_ electrons in the atoms in that column…thus, _____COLUMNS______ can also be labeled with their VALENCE NUMBERS. Let’s label our periodic charts with these numbers now. b) Elements in the same ___COLUMN_______ DO share similar chemical and physical properties. c) Example: Beryllium has _4__ electrons and _4___ protons. It has __5___ neutrons. 4 The Bohr model for Beryllium is: Be 9 It is located in column __2__. It therefore has __2__ electrons in its __VALENCE__ shell. The Bohr model proves this! Its VALENCE NUMBER is _2___. This means that it wants to __LOSE___ 2 electrons when it bonds with other atoms. 2. The periodic table has ___ROWS__________ or ____PERIODS_____. a) All the elements in the each ___PERIOD____________ have the same # of __ENERGY__ levels or shells. b) All elements in the same ___PERIOD____ do __NOT___ share similar chemical and physical properties. c) Example: 4 6 Beryllium and Carbon are both in period _2___. The both have _2__ energy Be C levels, but they do __NOT_ have similar chemical or physical properties (e.g. they 9 12 are not in the same __COLUMN_________)! 3. There are 4 major ___FAMILIES_______ or categories in the periodic table. Each ___FAMILY___ has a unique set of properties and characteristics. Because the periodic pattern in the periodic table is based upon the atomic ___NUMBER_____ and ___VALENCE________ number of the elements, the families are each located in specific areas on the periodic table. The chart below outlines these families, their physical and chemical FULL VALENCE SHELL! STABLE! Column 8 Noble or Inert Gases DO NOT WANT TO BOND! A little bit of both metallic and non-metallic properties except for AL On or below staircase Metalloids Opposite of metals Right of staircase Non-Metals corrodes Left of staircase Metals Lustrious, malleable, ductile, conduct and electricity, Location on Chart Family Chemical and Physical Properties properties, the types of bonds they make, and where they are located on the chart. A “CLOSER” LOOK AT THE STRUCTURE OF MATTER How do we illustrate the structure of the atom? GRAPHIC ORGANIZER PRACTICE