Unit 2 Atoms and Elements Grade 9 Science Period Ms. Hayduk Name: 1/36
Contents Atomic Structure... 4 The Particle Theory... 4 History of Atomic Theory... 4 Theories and Laws... 4 History of Atomic Theory... 5 Atomic Structure... 5 Current Atomic Theory... 5 Subatomic Particles... 5 The Atomic Model... 5 Activity: Atomic Models... 7 Chemical and Physical Properties... 9 Classifying Matter... 9 Classifying Matter Flow Chart... 10 Activity: Classifying Matter... 11 Physical and Chemical Properties... 14 Definition of Chemical and Physical Properties... 14 Qualitative and Quantitative Properties... 14 Chemical and Physical Properties... 14 Activity: Physical Properties... 17 Lab: Chemical Properties of Gases... 19 Elements and the Periodic Table... 21 The Periodic Table... 21 Development of the Periodic Table... 21 Classes of Elements... 21 Structure of the Periodic Table... 22 Families of Elements... 22 Elements on the Periodic Table... 24 Atomic Number... 24 Atomic Mass... 24 Element Symbols... 24 Activity: Elements and the Periodic Table... 25 Activity: Element Scavenger Hunt... 27 2/36
Atoms and Ions... 28 Atomic Number... 28 Electrons... 28 Bohr-Rutherford Diagrams... 28 Bohr-Rutherford Diagrams Practice... 29 Lewis Diagrams... 30 Ions... 30 Ion Notation... 30 Ion Rules... 30 Compounds... 31 Elements and Compounds... 31 Ionic Compounds... 31 Formulas and Names... 31 Activity: Elements and Compounds... 33 Physical and Chemical Changes... 34 Physical and Chemical Changes... 34 Activity: Physical and Chemical Changes... 35 3/36
Atomic Structure The Particle Theory The particle theory is used to explain many observable characteristics and properties of different substances. Before learning the particle theory, it is important to know the definition of matter: It can be solid, liquid, gas or plasma. The particle theory has four main tenets: Note that particles is a non-specific word. It can be used to mean:, which are particles of an element; or,, which are particles of a compound; or,, which are particles that have a positive or negative charge. History of Atomic Theory Theories and Laws A theory is: When new evidence is discovered that does not fit a theory, the theory is replaced or modified to fit the new facts. A law is: Generally, a law is considered to be fact, on the basis of many supporting observations and tests. Theories are used to explain laws. They do not become laws over time. 4/36
History of Atomic Theory Atomic theory is the theory that describes the nature of matter. It states that matter is made up of small units called. The model of the atom has changed significantly over time, based on theories from many scientists and critical thinkers. Atomic Structure Current Atomic Theory The particle theory, which we looked at earlier in the unit, is actually the currently accepted atomic theory. We know that all matter is composed of atoms. Also: Atoms of a specific element (like helium) are identical in size and mass. Atoms of different elements can combine together to make new substances. Subatomic Particles Atoms are not technically the smallest piece of matter. Subatomic particles are the components that make up an atom. Each has a specific purpose in the atom and in chemistry (and other sciences). There are three main subatomic particles:. Particle Mass Charge Location Electron Proton Neutron The Atomic Model In the current model of the atom, it is known that the protons and neutrons are in a tight mass in the centre of the atom, called the. The electrons orbit in a (relatively) huge around the nucleus, in different energy levels based on the number of electrons. Figure 1: Model of the atom 5/36
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Name: Date: Period: Due Date: Activity: Atomic Models Purpose To investigate contributions to atomic theory that led to the current model of the atom. Task Use pg. 152-153 in Saskatchewan Science 9 to fill in the chart below. All writing should be in your own words! Name Picture of Atomic Model Major Contribution to Atomic Theory John Dalton J.J. Thomson Ernest Rutherford Niels Bohr 7/36
Rubric Criteria Picture of Atomic Model Excellent Level Description Image is accurate. All parts of the model are shown and labeled. Evidence of effort drawing is neat and a ruler is used when necessary. Space is used well. Excellent 5 marks Pretty Good 4 marks Acceptable 3 marks Poor 2 mark Missing 0 marks Contribution to Atomic Theory Key contribution is summarized succinctly in student s own words. Points are accurate. 8/36
Classifying Matter A pure substance (e.g. oxygen gas, water) contains: Chemical and Physical Properties An element (e.g. iron) contains: A compound (e.g. salt sodium chloride) contains: Figure 2: Copper is an example of an element. A mixture (e.g. air, sand) contains A mechanical mixture (e.g. salad) is a mixture in which: A suspension (e.g. salad dressing, pop) is a mixture in which: Figure 3: Water is a compound, but glass is a solution since it contains three main compounds: silica, sodium oxide, and soda ash. A solution (e.g. salt water) is a mixture in which: There are two other terms that can be used to describe mixtures. Homogeneous mixtures look like one uniform substance. Heterogeneous mixtures look like multiple substances have been combined. These words have Latin origins: Homo- means same. 9/36
Hetero- means different. -geneous comes from the root genus, which means category or type. Classifying Matter Flow Chart 10/36
Name: Date: Period: Due Date: Activity: Classifying Matter Purpose To practice differentiating between elements, compounds and mixtures with reference to the terms homogeneous and heterogeneous Procedure 1. Examine each vial. There are fourteen, but you only need to observe eight. Do not open any vials! 2. For each vial, fill in the chart below. You need to have three observations for each vial. Use your classifying matter flowchart and the reference chart (page 13). 3. The vials contain the substances in the reference chart. Only these substances are included, but some vials may contain more than one of the substances. Observations Vial # Observations (3/vial) Classification (E, C, MM, Sol, Sus) Reasons for Classification Probable Identity of Substance(s) 11/36
Vial # Observations (3/vial) Classification (E, C, MM, Sol, Sus) Reasons for Classification Probable Identity of Substance(s) Evaluation (Observations) Criteria Great (5) Good (4) Average (3) Poor (2) Missing (0) Ability to make accurate scientific observations Ability to classify substances using logical thinking Discussion 1. Draw a picture that shows the difference at the particle level between a pure substance and a mixture (i.e. what would you see under a microscope?). (2 marks) Pure Substance Mixture 2. If you had no reference table of properties, what could you do to determine whether: (2 marks each) a. A clear, colourless liquid is pure water or a solution of salt in water? b. A clear, colourless liquid is alcohol or water? c. A reddish-brown metal is pure copper or a mixture of copper and tin? d. Which crystals are sugar or salt? 12/36
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Physical and Chemical Properties Definition of Chemical and Physical Properties So far, we have learned how to categorize substances based on the types of particles they contain. The next step is to determine characteristics that can help to identify what a substance is. These characteristics are called physical and chemical properties. Physical properties are characteristics of a substance that can be observed: Physical properties also include information on how a substance changes state. Chemical properties describe: Qualitative and Quantitative Properties Properties of matter can sometimes be subjective, meaning the actual observation might vary depending on the observer or the sample. Other times, properties may be exact and consistent for multiple samples and observers. Qualitative properties are: Quantitative properties are: Chemical and Physical Properties Chemical properties include: Chemistry is the study of chemical properties, and how different substances interact. Often, chemical properties are used to predict if a substance will participate in a chemical reaction. They can also be used to identify an unknown substance. 14/36
Physical properties include: Property Description Property Description Colour The first appearance, or colour, of a The ability of a substance to conduct Conductivity substance heat or electricity Lustre How shiny or dull a substance is Hardness The resistance of a substance to being scratched Melting Point The temperature at which a solid changes Freezing Point into a liquid (or a liquid turns into a solid) Texture The feel of the surface of a substance The temperature at which a liquid Boiling Point The ability of a solid to be stretched or changes into a gas (or a gas changes into a Malleability Condensation Point pounded into a sheet liquid) Density Solubility Ductility The mass of a substance in a given volume, or how tightly packed the particles are The maximum amount of a substance that can dissolve in another substance (usually water) The ability of a solid to be stretched into a wire Viscosity Odour Brittleness For examples of these properties, refer to Pearson Saskatchewan Science 9, pages 134-135. The resistance of a liquid or gas to flowing The smell of a substance The ability of a substance to be broken apart, as opposed to bent or molded Other physical properties can include crystal shape, state, size, shape, volume, temperature and mass. When describing physical properties of a substance, it is best to use as much detail as possible. 15/36
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Name: Period: Activity: Physical Properties Purpose To study elements and compounds to identify physical properties Date: Due Date: Procedure You will study five vials. Do not open any vials. Some contain very dangerous substances! For each, write: The name of the substance; Whether it is an element or a compound; and, Five physical properties you can see by observing it. Then, for each substance, use the Internet to look up: Two physical properties you could not observe. Observations Substance Physical Properties (Observed) Physical Properties (Researched) Evaluation (Observations) Criteria Great (5) Good (4) Average (3) Poor (2) Missing (0) Ability to make accurate and detailed scientific observations Ability to do accurate research 17/36
Discussion 1. Water is a substance that has many interesting properties that make it unique. Two properties that water has are called cohesion and adhesion. a. Look up these words in your textbook. Write the definition for each. (2 marks) Cohesion: Adhesion: b. The picture below show two test tubes: water (left) and mercury (right). Explain how you know which substance has better adhesion with glass. (2 marks) 2. Give two example of quantitative physical properties and two examples of qualitative physical properties. (4 marks) Quantitative: Qualitative: 18/36
Name: Date: Period: Lab: Chemical Properties of Gases Purpose To use chemical properties of various gases to identify the product gas of each chemical reaction. Materials Pipettes/dropper bottles Test tube Candle Wooden splint Scoopula Rubber stopper Tests Test 1: hydrogen peroxide (H 2O 2) + dry active yeast Test 2: acetic acid (vinegar, CH 3CO 2H) + sodium bicarbonate (baking soda, NaHCO 3) Test 3: hydrochloric acid (HCl) + magnesium (Mg) Properties of Gases Oxygen Hydrogen Carbon Dioxide Highly reactive Supports combustion (does not burn, but allows other things to burn) Oxidizes (rusts) metals Highly reactive Highly flammable Reacts with non-metals Not flammable; extinguishes fire Non-toxic Procedure 1. Use a scoopula to add a small amount of the solid reactant to a test tube. a. For yeast, add 3-4 grains. b. For baking soda, add a small scoop. c. For magnesium, add one 2-cm strip. 2. Use a pipette to add a small amount (less than 1 cm) of the liquid reactant to the same test tube. 3. Hold a stopper in the test tube and shake the reactants together. a. For test 1, shake for 10-20 seconds, then add a glowing splint. b. For test 2, shake for 5-10 seconds, then add a flaming splint. c. For test 3, shake for 5-10 seconds, then add a flaming splint. 4. Write down observations. 5. If the gas test is negative, repeat for the same substances until you have a positive test. 6. Dump out all products into the proper waste beaker and rinse the test tube with distilled water. Do not dump anything down the drain at your station! Observations Test 1 2 3 What gas? Why? 19/36
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Elements and the Periodic Table The Periodic Table Development of the Periodic Table In 1867, Dmitri Mendeleev began to collect information on all of the known elements at the time (63 of them) and started to sort the elements according to common properties: reactivity, colour, state, mass and density. As he organized, he began to identify a pattern. He hypothesized that gaps in the table represented elements that had not yet been identified yet, but whose properties could be predicted. Mendeleev s work led to the periodic law: This means that the periodic table isn t arranged randomly it is very logical! Classes of Elements Metals are located on the left side of the periodic table. General Properties of Metals: Non-metals are located on the right side of the periodic table. General Properties of Non-Metals: 21/36
Semi-metals, or metalloids, are located to the right of the middle of the periodic table, along the edge of the staircase. Semi-metals have properties of both metals and non-metals. One of the most common uses of semi-metals is in electronics, because they can conduct electricity in a controlled way. Structure of the Periodic Table A period is a: There are seven periods of elements. A group is a: It is also called a chemical family, because the elements in it have similar characteristics. Families of Elements There are four specially-named families. Alkali metals is the first group. They are: 22/36
Alkaline earth metals is the second group. They are: Halogens are the second last group. They are: Noble gases are the final group. These gases are all: Transition metals make up the centre block of the periodic table, from the 3 rd to the 12 th column. Lanthanides and actinides are in the separate two rows below the main part of the periodic table. 23/36
Elements on the Periodic Table Each block on the periodic table gives information about a specific element. On a standard table, there will be the element symbol, the element name, the atomic number and the atomic mass. Depending on the complexity of the periodic table, there may be additional information. Atomic Number The elements are arranged on the periodic table in order of increasing atomic number. The atomic number of an element is: Remember that for an atom, the number of electrons is equal to the number of protons! Atomic Mass The atomic mass is: It is equal to the number of protons and neutrons added together. On the periodic table, the atomic mass is actually: Isotopes are atoms with: Element Symbols Element symbols are vital for writing the names of compounds and in chemical reactions. It s really important to use the correct element symbol, with the right capital and lowercase letters. 24/36
Name: Date: Period: Due Date: Activity: Elements and the Periodic Table Purpose To observe samples of elements and determine some properties of these elements from the periodic table. Procedure For each station, examine the element inside the vial. Complete the table below for each element, using your periodic table and two reference sheets. DO NOT OPEN OR DROP ANY VIALS! Observations Element Name Symbol Atomic Number Atomic Mass State Origin of Name Common Use 1 2 3 4 5 6 7 8 9 10 11 12 Evaluation (Observations) Criteria Great (10) Good (8) Average (6) Poor (4) Missing (0) Chart is complete, correct and readable. 25/36
Discussion 1. Why are some of the symbols so different from the names of those elements? (1 mark) 2. There is a staircase on the right-hand side of the periodic table. a. What does this divide? (1 mark) b. What type of elements are on either side of the staircase? (1 mark) 3. How were the physical properties different for the metals and the non-metals that you observed? (1 mark) 4. Why do we not have a vial of: (1 mark each) a. Uranium? b. Bohrium? c. Fluorine? 5. If you found an unknown element, explain three ways that you could try to identify it. Assume it is not dangerous! (3 marks) 26/36
Name: Period: Activity: Element Scavenger Hunt Purpose To apply knowledge of the elements and the periodic table to objects in everyday life. Task For each clue, identify which element it is! Date: Clues Write the name and symbol for the element that is/has. 1. Atomic number 9 2. Atomic mass of 40.08 amu 3. The halogen in period 5 4. 19 protons 5. The fewest protons of the elements in group 10 6. The second lightest noble gas 7. Atomic number 30 8. The lightest element on the periodic table 9. Atomic mass of 16.00 amu 10. The alkaline earth metal in period 3 11. Element 6 as part of a compound 12. Element 6 as a pure substance 13. The heaviest semi-metal in group 14 14. Atomic mass of 196.97 amu 15. 26 electrons 16. 34 protons 17. Atomic number 16 18. The alkali metal in period 3 19. The semi-metal in group 14 with the fewest electrons 20. In period 2, group 15 21. Atomic mass 30.97 amu 22. The halogen with the second lowest mass 23. Atomic number 29 24. 47 electrons 25. On the staircase but is not a semi-metal 27/36
Atoms and Ions Atomic Number Recall that the atomic number of an element tells how many protons it has in its nucleus. For an atom (which has no charge), the number of electrons and protons are equal. Ions are: Electrons The placement and number of electrons in an atom will be very important when you start to look at chemical bonds and reactions. There are two ways to draw atoms and ions that give important details about the elements. Each is based on the placement of electrons in the atom. Bohr-Rutherford Diagrams The theory put forth by Niels Bohr and Ernest Rutherford claimed that electrons orbited in shells, or orbits, around the nucleus of the atom. Each shell could hold a specific number of electrons: Shell 1 2 3 4 Number of Electrons 2 8 8 18 To draw Bohr-Rutherford diagrams: As an example, use Mg. 1. Write the number of protons and neutrons in the centre. (Protons = atomic number, Neutrons = atomic mass atomic number, rounded to a whole number) 2. Draw a circle around the nucleus. 3. Draw the first shell, and put two electrons in it on opposite sides (10 left). 4. Add the second shell and draw 8 electrons in pairs (2 left). 5. Add the third shell and start with one electron at the top and one on the right. 28/36
Bohr-Rutherford Diagrams Practice Questions For each question, consider only the electrons in the outermost (valence) shell. How does the number of electrons change across a period (row)? What is the relationship between the group number and the number of electrons? What is the relationship between the period number and the number of shells? 29/36
Lewis Diagrams Lewis diagrams only show the chemical symbol and the valence electrons. Valence electrons are: The electrons are shown as dots starting on the right side and moving clockwise around the atom until it is filled with eight electrons. The octet rule states that: Examples: 1. H 2. Cl 3. Ne Ions Ions are formed when an atom gains or loses electrons. Non-metals (right side of the periodic table): Metals (left side of the periodic table): Ion Notation When an atom becomes an ion, it is written with the same symbol and the charge (how many electrons it gained or lost) as a superscript. Examples: Ion Rules 30/36
Compounds Elements and Compounds When two or more elements combine together, the resulting particle is called a. Individual particles of a compound are called. There are two main types of compounds: and Ionic Compounds Ionic compounds have a: The electrons in the of the metal atoms are to the valence shell of the non-metal atoms. This produces positive metal ions and negative non-metal ions, which are then attracted to each other. Most ionic compounds have properties that include: Covalent Compounds Covalent, or, compounds are made up of only non-metals. The electrons in their valence shells are with other non-metals, so that each atom has a full valence shell. These shared electrons form what are called. Most covalent compounds have properties that include: Formulas and Names Compounds can be written using a or a, but when reading them, they would sound the same. For example, an ionic compound is, but it can also be written as. This is table salt! The formula tells you what elements are in the compound, using the chemical symbol, and the number of atoms of each element, using subscripts. Examples: CaCl 2 K 2CO 3 NH 4NO 3 Fe(NO 3) 3 31/36
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Name: Period: Activity: Elements and Compounds Purpose To study the formulas and names of elements and compounds. Date: Due Date: Procedure For each vial, examine the substance inside. Complete the table below for each vial, using your periodic table. You only need to study ten vials. DO NOT OPEN OR DROP ANY VIALS! Observations Number and Types of Atoms in the Physical Properties (3) Substance Name Substance Example NH 4Cl 1 nitrogen, 4 hydrogen, 1 chlorine white, solid, granular 1 2 3 4 5 6 7 8 9 10 Evaluation (Observations) Criteria Great (5) Good (4) Average (3) Poor (2) Missing (0) Number of atoms column is complete and correct Three accurate and creative physical properties listed for each substance 33/36
Physical and Chemical Changes A physical change has occurred when: Physical and Chemical Changes A chemical change is characterized by: There are five ways to identify a chemical change has occurred. In general, more than one of these signs will be present. Sometimes odour is used as a sign of a chemical change, but this is only valid if it is a significant change in odour from the original reactants. For example, when fruit rots, it produces a bad odour much different from that of the original fruit. This is a sign of a chemical change. Figure 4: Rotten fruit If a new product is formed in a chemical change, a reaction has occurred. It can be written using the names or formulas of the elements and compounds that are used (reactants) and produced (products). The general form of a reaction can be written as: 34/36
Name: Period: Activity: Physical and Chemical Changes Purpose To identify physical and chemical changes Date: Due Date: Procedure At each station, follow the directions exactly as they are written. Record your observations in the chart below. Safety 1. Handle all materials with extreme caution! Do not mix anything unless you are specifically asked to do it! 2. Wear safety glasses at all times. 3. Do not leave lit Bunsen burner unattended. If you are uncomfortable with the Bunsen burner, please ask Ms. Hayduk to help! Observations Physical or Station Chemical Change? Evidence and Observations 1 2 3 4 5 6 7 8 9 10 Evaluation (Observations) Criteria Great (10) Good (8) Average (6) Poor (4) Missing (0) Observations are complete, accurate, thorough and readable. 35/36
Discussion 1. What are the five signs of a chemical change? (5 marks) 2. The main sign of a chemical change is that a new substance is produced. This is important because sometimes one of the signs of a chemical change can be present when a physical change is actually what is happening. Fill in the chart below. (6 marks) Observation Example of Chemical Change Example of Physical Change Heat is produced or absorbed Ammonium nitrate is dissolved in water Ice melts into water Bubbles are produced There is a colour change A solid forms 3. State two physical properties and two chemical properties of magnesium. (4 marks) Physical Properties Chemical Properties 36/36