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Chemistry test Review Crossword Puzzle answers – Across 3. Groups 4. Periods 9. Noble gases 12.Metalloids 13.Number 16.Valence electrons 21.Reactivity 22.Transition 24.Properties 25.Neutral 26.metals Crossword Puzzle Answers - Down 1. Ductility 2. Proton 5. Element 6. Conductivity 7. Semiconductors 8. Halogens 10.Atom 11.ion 14.Electron 15.Malleable 17.Negative 18.Alkali 19.Mass 20.Brittle 21.nucleus Study Guide Answers 1. Who were the three men we discussed who contributed to the current Atomic Theory (what we know about atoms)? What did each man contribute? • Democritus – • Thomson – • First determined there was such a thing as an atom Discovered the negatively charged particles we now call electrons Rutherford – Discovered that there is a positively charged nucleus at the center of the atom 2. Describe, in detail, the three part of the atom (size, location, charge, etc…) • Proton – Positively charged, large particles (1amu) found in the nucleus at the center of the atom • Neutron – Neutrally charged, large particles (1 amu) found in the nucleus at the center of the atom • Electron – Negatively charged, small particles (0 amu) found in electron clouds that circle the nucleus 3. What unit is used to measure the mass of an atom or its parts? Is this the same general unit we use for everything else? Why/why not? • Amu – Atomic mass unit • It is not the same as a gram – Because atoms and their particles are way too small to use the normal mass measurement system so scientists had to come up with a new way to measure their mass 4. Explain the difference between atomic number and atomic mass • Atomic number – Describes how many protons are in the nucleus of an atom – Also describes the number of electrons in a neutral atom • Atomic mass – Describes the sum of the number of protons and neutrons in the nucleus of the atom 5. Write your own definition for element and pure substance (do not use the book definition!!!!) 6. Why can’t two elements have the exact same properties? - because they would no longer be different if they had exactly the same properties - two elements can share some similar properties, but they must have at least one property different from each other in order to be different from each other 7. If you were given samples of two different elements, but they were not labeled, how could you determine what they are? • Density • Color • Melting point • Boiling point • texture 8. Describe the three types of elements • Metals – Shiny, ductile (pulled into wires), malleable (hammered into thin sheets), good conductors of heat and electricity • • Nonmetals – Dull, brittle (shatter easily), poor conductors • • To the left of the zigzag line on the periodic table To the right of the zigzag line on the periodic table Metalloids – – Also known as semi-conductors Have properties of both metals and nonmetals • On the zigzag line on the periodic table 9. What was different between the periodic tables Mendeleev and Mosely created? Whose periodic table do we still use today? • Mendeleev used increasing atomic mass to organize the table – There were gaps in some places • Mosely used increasing atomic number – This is the organizational method we still use today 10. What type of element is Rhenium (Re), atomic number 75? How do you know? • It is a metal – It is located within the transition metals – It is to the left of the zigzag line 11. What pieces of information can you obtain from each entry in the periodic table? • Atomic number – # of protons in the atom • Atomic mass – # of protons and neutrons in the atom • • Element name Element (chemical) symbol – One or two letters 12. Find Terbium (Tb) on the periodic table. How many protons are in one atom of Terbium? Electrons? Neutrons? • Atomic # is 65, atomic mass is 159 • Protons – 65 • Electrons – 65 • Neutrons - 94 13. How many valence electrons would an atom of Astatine (At) have? How do you know? • At would have 7 valence electrons – It is a member of the halogen group (group 17) 14. Is Astatine a reactive element or not? How do you know? • It is highly reactive • Because it is in group 17 and has 7 valence electrons – Group 17 elements want to quickly fill up their outermost orbital and have 8 valence electrons to be “happy” 15. What are the names of the rows and columns in the periodic table? How many of each are there? • Horizontal rows are called periods – There are 7 periods • Vertical columns are called groups or families – There are 18 groups