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Alkali metal wikipedia , lookup
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Enduring Understandings As matter and energy cycle through systems, atoms and molecules are transformed and recombined in different ways. Technical Reading Dmitri Did It! Concepts Important to Know and Understand Energy stored and released through chemical bonds EQ: How does a system maintain balance? Broad Brush Knowledge properties of matter Targeted Skills Communication Determine purpose gather information Analyze words identify context clues Purpose Core Objectives 4 Identify the structure and properties of atoms and elements. 5 Determine properties used to position an element within the periodic table. 6. Identify the transformations of atoms, molecules, and energy that occur within cycles in the environment. Gather information and develop technical reading skills. Expert Information: Dmitri Mendeleev was a Russian scientist who lived in the 1800’s. Only 60 elements were discovered during his lifetime. In 1869, Mendeleev organized the information known about these elements and created a chart called the periodic table of the elements. Since that time, fifty-six additional elements have been discovered and added to the chart. Scientists all over the world use the same periodic table. + - electrons + + - nucleus 3 protons Li neutrons energy levels Atomic structure of lithium Lithium 6.941 Atomic number = number of protons Atomic mass = number of protons + neutrons Periodic table entry for lithium Compare the atomic structure of lithium to its position on the periodic table. Since an atom of lithium has three protons, lithium’s atomic number is 3. Three neutrons plus three protons in the nucleus results in lithium having an atomic mass of 6. Not all atoms of an element are identical. Some lithium atoms have additional neutrons, which causes these atoms, called isotopes, to have greater mass. Atomic mass is the average mass of all isotopes of an element. Elements are arranged on the periodic table by their atomic numbers. Typically, atomic numbers are in the same order as atomic masses. The periodic table is a grid of rows and columns. The seven rows are called periods. Each atom of an element in a period has the same number of energy levels. Lithium has two energy levels, so it occurs in period two. Each of the 18 columns is a group, or family, of elements. All of the elements in a group have many similar chemical properties. These similarities occur due to the elements in a group having the same number of electrons in the outer energy level. Elements are classified into two groups—metals and nonmetals. The stair-step line on the periodic table separates metals on the left from nonmetals on the right. There are more metals than nonmetals. Metals share certain physical properties such as the ability to conduct heat and electricity. Metals can be formed into shapes. Nonmetals usually do not conduct electricity and cannot be formed into shapes. © 2006 Plano ISD, Plano, TX/Klein ISD 2007© 1 Find each of these elements on the periodic table and fill in the missing information. Period Group 3 2 2 18 5 11 7 1 6 14 Element Symbol Atomic Number 1. What is the lightest element on the chart above? What is its atomic number? 2. What term refers to rows of elements? 3. What term refers to columns of elements? 4. Do groups or periods classify elements that have similar properties? 5. On the periodic table, where are metals listed? 6. On the periodic table, where are nonmetals listed? 7. Are there more metals or nonmetals? 8. How are elements listed on the periodic table? Find each of these elements on the periodic table and fill in the missing information. Period Group Element Symbol Atomic Number osmium beryllium arsenic zinc nitrogen 9. Which of these elements are metals? 10. Which of these elements are nonmetals? 11. List two elements that have many similar properties. 12. Why do these two elements have many similar properties? © 2006 Plano ISD, Plano, TX/Klein ISD 2007© 2