16 Elements and the Periodic Table

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16 Elements and the Periodic Table Key Vocabulary atom atomic mass chemical formula compound element family molecule

16 Elements and the Periodic Table Of the four families you investigated, which two seem the most alike? Which one seems the most different from the others? What kinds of properties can you use to distinguish groups of elements? Record your answers in your notebook.

16 Elements and the Periodic Table Read the introduction and look for key ideas Think of the world around you. Everything—from the air you breathe to the shoes you walk in—is made from elements or combinations of elements.

16 Elements and the Periodic Table What are elements, and how do they relate to compounds?

16 Elements and the Periodic Table Complete the procedure Be sure to complete the Stopping to Think questions.

16 Elements and the Periodic Table Stopping to think 1 a.In what ways were the ancient Greek philosophers right about elements? b.In what ways were the ancient Greek philosophers wrong?

16 Elements and the Periodic Table Stopping to think 2 a.How did Mendeleev build on other scientists’ work? b.How did other scientists build on Mendeleev’s work?

16 Elements and the Periodic Table Stopping to think 3 Use the Periodic Table of the Elements on the next page to decide whether each of the following is a metal or nonmetal: lithium (Li), carbon,(C), sulfur (S), calcium (Ca), titanium (Ti), and bromine (Br).

16 Elements and the Periodic Table Stopping to think 4 Find magnesium on the periodic table. What is magnesium’s chemical symbol? What family does magnesium belong to? Is magnesium a solid, a liquid, or a gas? Based on its family, would you expect magnesium to be very reactive, somewhat reactive, or not reactive at all?

16 Elements and the Periodic Table Stopping to think 5 What are two ways that compounds are different form the elements that form them?

16 Elements and the Periodic Table Stopping to think 6 The chemical formula for baking soda is NaHCO 3. What elements are in baking soda? How many of each kind of atom is represented by the formula for baking soda?

16 Elements and the Periodic Table What have you learned about the organization of the periodic table?

16 Elements and the Periodic Table Analysis question 1 Make a copy of the table below in your science notebook. Use the Periodic Table of Elements to find out which atoms make up a molecule for each of the substances listed. The first row has been completed for you.

16 Elements and the Periodic Table Analysis question 2 Sodium is a metallic solid, and chlorine is a poisonous yellow-green gas. Sodium and chlorine react to form sodium chloride, which is common table salt. a. Is table salt an element or a compound? Explain. b. Describe the physical properties of table salt. c. How do the properties of table salt compare with those of sodium and chlorine?

16 Elements and the Periodic Table Analysis question 3 Is seawater an element, compound, or mixture? Explain your answer.

16 Elements and the Periodic Table Analysis question 4 Explain the relationship between an atom and a molecule.

16 Elements and the Periodic Table What are elements, and how do they relate to compounds?

16 Elements and the Periodic Table Key vocabulary definitions Atom - The basic structural unit of an element. Atomic mass - The average mass of atoms of an element; also known as atomic weight.

16 Elements and the Periodic Table Key vocabulary definitions Chemical formula - A shorthand notation to describe elements and compounds and their reactions. Each element is identified by one or two letters. For example, H represents hydrogen, Cl represents chlorine, and O represents oxygen. A compound is identified by its combination and proportion of elements. For example, H 2 O represents water. Reactions are represented as equations with an arrow indicating direction of change instead of an equals sign. For example, the reaction between hydrochloric acid and sodium hydroxide to produce water and sodium chloride is represented by HCl + NaOH ⇛ H 2 O + NaCl.

16 Elements and the Periodic Table Key vocabulary definitions Compound - A homogeneous, pure substance composed of two or more essentially different elements that are chemically combined and that are thus present in definite proportions. For example, H 2 O contains two atoms of hydrogen and one atom of oxygen chemically combined to produce a new substance with properties quite different from either hydrogen or oxygen.

16 Elements and the Periodic Table Key vocabulary definitions Element - A substance that cannot be broken down into simpler substances by chemical or physical means. Family - Elements with similar chemical properties arranged in the same column of the periodic table.

16 Elements and the Periodic Table Key vocabulary definitions Molecule - The smallest particle of an element or compound that displays the properties of the substance in quantity.

16 Elements and the Periodic Table For links to learn more about Dmitri Mendeleev’s work and the work of other chemists, visit the SEPUP website: