1. PERIODIC TABLE

2. Chapter Fifteen: Elements and the Periodic Table  15.1 The Periodic Table of the Elements  15.2 Properties of the Elements

3. Chapter 15.1 Learning Goals  Differentiate physical and chemical properties of elements.  Explain how the periodic table is organized.  Identify metals, semimetals, and nonmetals on the periodic table.

4. Investigation 15A  Key Question: How is the periodic table organized? The Periodic Table

5. 15.1 Physical properties  Characteristics that you can see through direct observation are called physical properties.  Physical properties include color, texture, density, brittleness, and state (solid, liquid, or gas).  Melting point, boiling point, and specific heat are also physical properties.

6. 15.1 Physical properties  A physical change does not result in a new substance being formed.

7. 15.1 Chemical properties  Properties that can only be observed when one substance changes into a different substance are called chemical properties.  Any change that transforms one substance into a different substance is called a chemical change.

8. 15.1 The Periodic Table  The periodic table organizes the elements according to how they combine with other elements (chemical properties).  The periodic table is organized in order of increasing atomic number.

9. 15.1 The Periodic Table  The periodic table is further divided into periods and groups.  Each horizontal row is called a period.  Each vertical column is called a group.

10. 15.1 The Periodic Table  All the elements in Group 1 of the periodic table form similar compounds.  The metals lithium, sodium, and potassium all form compounds with a ratio of 2 atoms of the metal to 1 atom of oxygen.

13. 15.1 Atomic Mass  The mass of individual atoms is so small that the numbers are difficult to work with.  To make calculations easier, scientists use the atomic mass unit (amu).  The atomic mass of any element is the average mass (in amu) of an atom of each element.

14. 15.1 Atomic Mass  Atomic masses differ from mass numbers because most elements in nature contain more than one isotope.

15. 15.1 Atomic Number  Remember, the atomic number is the number of protons all atoms of that element have in their nuclei.  If the atom is neutral, it will have the same number of electrons as protons.

16. 15.1 Groups of the periodic table  The first group is known as the alkali metals.  The alkali metals are soft and silvery in their pure form and are highly reactive.  This group includes the elements lithium (Li), sodium (Na), and potassium (K).

17. 15.1 Groups of the periodic table  The group two metals include beryllium (Be), magnesium (Mg), and calcium (Ca).  They also bond easily with oxygen.

18. 15.1 Halogens  The halogens tend to be toxic gases or liquids in their pure form.  Fluorine (F), chlorine (Cl), and bromine (Br) form salts when the bond with alkali metals.

19. 15.1 Noble Gases  The noble gases, including the elements helium (He), neon (Ne), and argon (Ar).  These elements do not naturally form chemical bonds with other atoms and are almost always found in their pure state.

21. Chapter Fifteen: Elements and the Periodic Table  15.1 The Periodic Table of the Elements  15.2 Properties of the Elements

22. Chapter 15.2 Learning Goals  Differentiate the electrical and thermal conductivity of metals and nonmetals.  Define periodicity and discuss examples.  Predict properties of an element based on its position on the periodic table.

23. Investigation 15B  Key Question: What information can you get from the periodic table? Atomic Challenge

24. 15.2 Properties of the elements  Most of the pure elements are solid at room temperature.  Only 11 naturally occurring elements are a gas.  Only 2 elements (Br and Hg) are liquid at room temperature.

25. 15.2 Periodic properties of elements  Periodicity means properties repeat each period (row) of the periodic table.

26. This pattern is an example of periodicity.

27. 15.2 Thermal and electrical conductivity  Electricity is the movement of electric charge, usually electrons.  Some materials allow electrons to flow easily through them.  We call these materials electrical conductors.

28. 15.2 Thermal and electrical conductivity  Like copper, most metals are good thermal conductors.  That is one reason pots and pans are made of metal.

29. 15.2 Thermal and electrical conductivity  Elements on the far right of the table are called non- metals.  Nonmetals make good insulators.  An insulator is a material which slows down or stops the flow of either heat or electricity.

30. 15.2 Metals and metal alloys  An alloy is a solid mixture of one or more elements.  Most metals are used as alloys and not in their pure elemental form.  Yellow brass is an alloy of 72% copper, 24% zinc, 3% lead, and 1% tin.

31. 15.2 Metals and metal alloys  Titanium combines the strength and hardness of steel with the light weight of aluminum.  Titanium, a rare and expensive alloy, is used for military aircraft and racing bicycles.

32. 15.2 Carbon and carbon-like elements  Almost all the molecules that make up plants and animals are constructed around carbon.  The chemistry of carbon is so important it has its own name, organic chemistry.

33. 15.2 Carbon and carbon-like elements  Pure carbon is found in nature as either graphite or diamond.  Silicon is the second most abundant element in the Earth’s crust, second only to oxygen. Why are carbon and silicon important?

34. 15.2 Nitrogen, oxygen and phosphorus  Oxygen and nitrogen are crucial to living animals and plants.  For example, proteins and DNA both contain nitrogen.  Phosphorus is a key ingredient of DNA, the molecule responsible for carrying the genetic code in all living creatures.

35. 15.2 Nitrogen, oxygen and phosphorus  Proteins and DNA both contain oxygen and nitrogen, making these elements crucial to life.  46% of the mass of Earth’s crust is also oxygen bound up in rocks and minerals.

36. 15.2 Nitrogen, oxygen and phosphorus  Phosphorus is a key ingredient of DNA, the molecule responsible for carrying the genetic code in all living creatures.  When phosphorus atoms absorb light, they store energy, then release it in a greenish glow.

37. Investigation 15C  Key Question: How do electrons fill up the energy levels? Electrons and the Periodic Table

38. Silicon- The Super Element  Although silicon can form a myriad of useful compounds, it’s best known for its impact on the modern world in the form of the microchip, a miniaturized electric circuit that fits into computers, cellular telephones, microwaves, and other digital appliances.