Chapter Menu Section 4.1 The Variety of Compounds Section 4.2 How Elements Form Compounds Click a hyperlink to view the corresponding slides. The Variety of Compounds • Distinguish the properties of compounds from those of the elements of which they are composed. • Compare and contrast the properties of sodium chloride, water, and carbon dioxide. • Predict whether two elements will react to form a compound. The Variety of Compounds chemical property: a property that can be observed when there is a change in the composition of a substance. The properties of compounds differ from the properties of the elements that form the compounds. MQ Monday, October 7, 2019 1. 5 facts (in full sentences) from section 4.1 MQ Tuesday, October 8, 2019 1. How does sodium chloride occur naturally? 2. Name 2 physical properties of sodium chloride. 3. Name 2 physical properties of carbon dioxide. 4. What do you call the study of carbon compounds? 5. Name 2 physical properties of hydrogen. Table Salt (NaCl) • Table salt, or sodium chloride, is so abundant on Earth, it is used to manufacture the elements sodium and chloride. Table Salt (cont.) • Properties of table salt – white, cubed crystals at room temperature – crystals are hard but brittle and do not conduct electricity – When salt is heated to a temperature of about 800°C, it melts and forms liquid salt which does conduct electricity. Table Salt (cont.) • Salt easily dissolves in water—the resulting solution is an excellent conductor of electricity. • Salt does not react readily with other substances. Table Salt (cont.) • Properties of sodium – shiny, silvery-white, soft, solid metallic element that melts when heated above 98°C – Because of its high reactivity, the free element sodium is never found in the environment but is always found combined with other elements. Table Salt (cont.) • Properties of chlorine – pale green, poisonous gas with a choking odor that kills living cells and is slightly soluble in water – it is a nonmetal that must be cooled to -34°C before it turns to a liquid – highly reactive and used for many industrial processes Carbon Dioxide • Carbon dioxide is a gas that is an important link between the plant and animal world. Carbon Dioxide (cont.) – used to put out fires since it does not support burning – it is necessary for photosynthesis Carbon Dioxide (cont.) • Properties of carbon – nonmetal that is fairly unreactive at room temperature but reacts with many other elements at higher temperatures – excellent source of heat – the majority of compounds that make up living things contain carbon Carbon Dioxide (cont.) • Properties of oxygen – a nonmetal that is a colorless, odorless, and tasteless gas – becomes a liquid at –183°C and is slightly soluble in water – is the most abundant element in the Earth’s crust, but typically combined with other elements – more reactive than carbon Carbon Dioxide (cont.) Water • Dihydrogen monoxide, better known as water, covers approximately 70 percent of Earth’s surface and also makes up about 70 percent of the mass of the average human body. Water (cont.) • Properties of water – occurs in Earth’s environment in all three common states(solid, liquid, and gas) – freezes into a solid at 0°C and becomes a gas at 100°C – does not conduct electricity in any of its states – universal solvent Water (cont.) – stable compound that does not break down under normal circumstances and does not react with many other substances – nearly all the chemical reactions in the human body and many important reactions on Earth occur in an aqueous solution Water (cont.) • Properties of hydrogen – colorless, odorless, and tasteless gas which is the lightest and most abundant element in the universe – usually classified as a nonmetal that does not conduct electricity and is only slightly soluble in water Water (cont.) – reactive element that usually occurs in a variety of compounds – turns into a liquid at –253°C Using clues to make a case • Macroscopic properties provide clues about what happens on the submicroscopic level. Section Assessment The majority of compounds that make up living things contain ___. A. oxygen B. carbon C. sulfur D. sodium Section Assessment Rusting is a prime example of which element’s reactivity? A. iron B. carbon C. oxygen D. hydrogen MQ Thursday, October 10, 2019 1. It is highly unlikely that atomic nuclei would ever collide. True or False. 2. What is the octet rule? 3. What is the noble gas configuration? 4. What do you call a compound that is composed of ions? 5. What do you call the strong attractive force between ions? MQ Friday, October 11, 2019 1. Just write your name on a paper and quickly turn it in with your homework. MQ Monday, October 14, 2019 1. What classes combine to form an ionic compound? 2. What classes normally combine to form a covalent compound? 3. What do you call an uncharged group two or atoms held together by covalent bonds? 4. When charcoal burns, carbon atoms collide with oxygen to form CO2. True or False. 5. Why are the attractive forces between covalent compounds usually weak? MQ Monday, October 14, 2019 1. What classes combine to form an ionic compound? Nonmetal with metal 2. What classes normally combine to form a covalent compound? Nonmetal with nonmetal 3. What do you call an uncharged group two or atoms held together by covalent bonds? Molecule 4. When charcoal burns, carbon atoms collide with oxygen to form CO2. True or False. 5. Why are the attractive forces between covalent compounds usually weak? IF are much weaker than the ionic charge that holds ionic compounds together. How Elements Form Compounds • Model two types of compound formation: ionic and covalent at the submicroscopic level. • Demonstrate how and why atoms achieve chemical stability by bonding. • Compare, using examples, the effect of covalent and ionic bonding on the physical properties of compounds. How Elements Form Compounds valence electron: an electron in the outermost energy level of an atom How Elements Form Compounds octet rule covalent bond noble gas configuration covalent compound ion molecule ionic compound electrolyte ionic bond interparticle force crystal Compounds form when electrons in atoms rearrange to achieve a stable configuration. Atoms Collide • When substances react, particles of the substances must collide. • Reactions between atoms involve only their electron clouds. Chemical Stability • Group 18 elements, also known as the noble gases, almost completely lack chemical reactivity. • Each noble gas has eight valence electrons, except for helium, which has two. Chemical Stability (cont.) • The octet rule is the model of chemical stability that states that atoms become stable by having eight electrons in their outer energy level except for some of the smallest atoms, which have only two electrons (duet rule). Chemical Stability (cont.) • A noble gas configuration is the state of an atom achieved by having the same valence electron configuration as a noble gas atom, which is the most stable configuration. Chemical Stability (cont.) Ways to Achieve Stability • When elements combine, they form either ions or molecules. • Atoms try to form the octet (or duet) by gaining or losing valence electrons. Ways to Achieve Stability (cont.) • An ion is an atom or group of combined atoms that has a charge because of the loss or gain of electrons. • A compound that is composed of ions is called an ionic compound. Ways to Achieve Stability (cont.) Ways to Achieve Stability (cont.) • The strong attractive force between ions of opposite charge is called an ionic bond. • A crystal is a regular, repeating arrangement of atoms, ions, or molecules. • Solid substances are composed of crystals. Ways to Achieve Stability (cont.) • In order for a solid, such as sodium chloride, to melt, its temperature must be raised until the motion of the particles overcomes the attractive forces and the crystal organization breaks down. Ways to Achieve Stability (cont.) • Chemical formulas indicate what elements make up the compound and how many atoms of each element are present in one unit of the compound. Ways to Achieve Stability (cont.) Ways to Achieve Stability (cont.) • Atoms can also share valence electrons to achieve a stable octet. Ways to Achieve Stability (cont.) • The attraction of two atoms for a shared pair of electrons is called a covalent bond. • A compound whose atoms are held together by covalent bonds is a covalent compound. • A molecule is an uncharged group of two or more atoms held together by covalent bonds. Ways to Achieve Stability (cont.) • Two nonmetallic elements usually achieve stability by sharing electrons to form a covalent compound. • If the reacting atoms are a metal and a nonmetal, they are much more likely to transfer electrons and form an ionic bond. Ways to Achieve Stability (cont.) • In addition to double bonds, atoms can form triple bonds. How do ionic and covalent compounds compare? • The strong attractions among positive and negative ions in an ionic compound result in a strong, three-dimensional crystal structure that is hard, brittle, and must be heated to high temperatures to melt. How do ionic and covalent compounds compare? (cont.) • Ionic compounds are electrolytes, compounds that conduct electricity when melted or dissolved in water. • The attractive forces between molecules of a covalent compound are weak because the molecules themselves have no charge. How do ionic and covalent compounds compare? (cont.) • Interparticle forces, or the forces between particles that make up a substance, are the key to determining the state of matter of a substance. • The difference in strength of the interparticle forces in covalent compounds compared to ionic compounds explains differences in their properties. Section Assessment What determines the state of matter of a substance? A. interparticle forces B. ionic bonds C. covalent bonds D. the ability to conduct electricity Section Assessment All ionic compounds are ___ at room temperature. A. solids B. liquids C. gases Chemistry Online Study Guide Chapter Assessment Standardized Test Practice Image Bank Concepts in Motion Key Concepts • When compounds form, they have properties that differ greatly from the properties of the elements of which they are made. • Atoms combine in different ways to form different kinds of compounds. • The properties of compounds differ widely because of differences in what happens to their constituent atoms when they form. • Macroscopic properties provide clues about what happens on the submicroscopic level. Key Concepts • Atoms become stable by reacting to achieve the outer-level electron structure of a noble gas (Group 18). • To achieve stability, some atoms transfer electrons to another atom, thus forming charged ions of opposite charge. The ions attract each other and form an ionic compound. • Some atoms share electrons to form covalent compounds. • Two atoms can share more than one pair of electrons. • In ionic compounds, the interparticle forces are attractions between ions of opposite electric charge. They are much stronger than the interparticle forces between molecules of covalent compounds. Photosynthesis is probably the most significant chemical reaction of ___. A. oxygen B. carbon C. carbon dioxide D. sodium chloride In their elemental state, which group has a complete octet of valence electrons? A. alkali metals B. alkaline earth metals C. halogens D. noble gases What forms when a metallic element and a nonmetallic element are combined? A. ionic bond B. covalent bond C. covalent compound D. noble gas configuration What is another name for a molecular bond? A. molecule B. ionic bond C. covalent bond D. covalent compound Why are solid ionic compounds poor conductors of electricity? A. They are nonmetals. B. They have electrons that cannot flow freely. C. They are electrolytes. D. Solids do not conduct electricity. What is the electrostatic charge holding two ions together? A. ionic bond B. covalent bond C. covalent compound D. crystal lattice bond Why are the attractive forces between molecules of a covalent compound weak? A. The molecules have no charge. B. The molecules form ionic bonds. C. interparticle forces D. They lack electrolytes. A(n) ___ is a regular, repeating arrangement of atoms, ions, and molecules. A. pattern B. crystal C. lattice D. octet Which element would not be commonly used in a neon light display? A. hydrogen B. argon C. helium D. radon A(n) ___ is an uncharged group of two or more atoms held together by covalent bonds. A. ion B. crystal C. electrolyte D. molecule Click on an image to enlarge. Figure 4.17 Na/Cl ionic bond Figure 4.24 Electrolytes To use this Interactive Chalkboard product: Click the Forward button to go to the next slide. Click the Previous button to return to the previous slide. Click the Home button to return to the Chapter Menu. Click the Return button in a feature to return to the main presentation. Click the Exit button or press the Escape key [Esc] to end the slide show. Click the Help button to access this screen. Click the Chapter Resources button to view available resources for the chapter. These resources include Chemistry Online, Study Guide, Chapter Assessment, Standardized Test Practice, Image Bank, and Concepts in Motion. Concepts in Motion pieces can also be accessed on relevant lecture note slides. This slide is intentionally blank.
