Unit 2: Chemical bonding and reactions Module 6: Ionic compounds and metals Lesson 1: Ion formation BP:168 Focus Question Why do elements form compounds? New Vocabulary Chemical bond Cation Anion Review Vocabulary Octet rule: atoms tend to gain, lose, or share electrons in order to acquire eight valence electrons. Valence Electrons and Chemical Bonds The coral reef is formed from a compound called calcium carbonate, which is just one of the thousands of compounds found on earth. How do so many compounds form from the relatively few elements known to exist? The answer involves the electron structure of atoms and the nature of the forces between atoms Valence Electrons and Chemical Bonds You know that elements within a group on the periodic table have similar properties. Many of these properties depend on the number of valence electrons the atom has. These valence electrons are involved in the formation of chemical bonds between 2 atoms. A chemical bond is the force that holds 2 atoms together. This chapter discusses chemical bond formed by ions, atoms that have acquired a positive or negative charge https://www.youtube.com/watch?v=x1gdfkvkPTk Valence Electrons and Chemical Bonds • Lewis developed electron dot diagrams as a simple way to show and keep track of valence electrons • Electron-dot structures can be used to illustrate the formation of chemical bonds. Engage: Valence electrons and chemical bonds 1- Draw the arrangement of electrons in energy levels around nucleus. Identify the number of valence electrons and electron dot diagram of each of the following elements: Calcium, Chlorine and Argon. Element Arrangement of electrons in energy levels around nucleus Valence electrons Calcium Chlorine Argon 2- What must calcium do to acquire 8 valence electrons ? 3- What must chlorine do to acquire 8 valence electrons? Electron Dot Diagram Valence Electrons and Chemical Bonds • Elements tend to react to acquire the stable electron structure of a noble gas. • Atoms try to form an octet—a stable arrangement of eight valence electrons in the outer energy level—by gaining or losing valence electrons. Watch the following video, and describe how the bond in NaCl is formed and why ? https://www.youtube.com/watch?v=lhC42qxk5kQ&t=48s Explore and explain: Positive Ion Formation Alkali metals (Group 1) tend to lose one electron to form 1+ ions. Sodium forms many common compounds including salt and baking soda The alkaline earth metals (Group 2) tend to lose 2 electrons and form 2+ ions. Elemental beryllium is a hard brittle metal. In nature, beryllium is found combined with other elements to form a variety of minerals, such as beryl Explore and explain: Positive Ion Formation Some Transition metals form several different ions. For example copper, shown here as a native mineral, commonly 1+ and 2+ ions in compounds. Positive Ion Formation Metals, which are located on the left side of periodic table, easily lose electrons A positive ion forms when an atom loses one or more valence electrons in order to attain a noble gas configuration. A positively charged ion is called a cation. Positive Ion Formation • • This figure illustrates how sodium loses a valence electron to become a sodium cation. By losing an electron, the sodium atom acquires the stable outer electron configuration of neon. Analyze: Does the removal of an electron from a neutral atom require energy or release energy? Positive Ion Formation • Metals atoms are reactive because they lose valence electrons easily. Group 1 and 2 metals are the most reactive metals. • The ions formed by metal atoms in groups 1, 2, and 13 are summarized below. Group Charge of ion formed 1 (lose 1 electron) 1+ 2 (lose 2 electrons) 2+ 13 (lose 3 electrons) 3+ Positive Ion Formation Most transition metals ,group 14 metals and some of group 13 metals form ions with charge of +2, +3 or more The following table shows the most common one. Positive Ion Formation Use Graphic organizers In your chemistry journal, make a chart with the following column heads: Symbol of element, electron dot diagram, Ion with charge, number of electrons Lost or gained, and name of ion. Complete the table using the elements Cesium, barium, Zinc, Phosphorus, copper, Iron, Chromium Negative Ion Formation While metals tend to form positive ions, nonmetals tend to form negative ions. For nonmetals, you can usually predict the charge of the negative ion that an element will form simply by looking at the element’s group on the periodic table. Explore and explain: Negative ion formation Carbon, seen here in one of its elemental forms, is in group 14. From this, you might predict that it will form a 4- ion. While this is possible, the ion is very unstable and uncommon. Explore and explain: Negative ion formation Elemental phosphorus has 2 major forms- white and red. When phosphorus ionizes, it tends to form 3- ions. Notice phosphorus’s position in group 15 Explore and explain: Negative ion formation Oxygen from group 16, tends to form 2- ions. Explore and explain: Negative ion formation Bromine, a brown liquid in its elemental form, is in group 17. Group 17 elements tend to be very reactive, easily forming 1ions. https://wordwall.net/resource/255 5489 https://wordwall.net/resource/332 76668 Negative Ion Formation • The figure shows chlorine gaining an electron. This process releases 449 KJ/mol • An anion is a negatively charged ion. Thus, the chlorine atom becomes a chloride anion. Compare How do the energy changes accompanying positive ion and negative ion formation compare? Negative Ion Formation • As shown in the table, nonmetal ions gain the number of electrons required to fill an octet valence shell Group Charge of ion formed 15 3- 16 2- 17 1- Naming monatomic ions (one atom ion) Cations of Group 1, and 2 metals: Name of the metal + “ion” Example: Na+ is sodium ion Transition metals cations: “ion ” Metal name + Roman numerals + Example: Fe3+ is iron (III) ion Anion names: Nonmetal root name + “-ide ” + ion Example: Cl- is chloride ion Elaborate https://quizizz.com/admin/quiz/6242f4d745 c4e8001d6d76ac?source=quiz_share Answer the focus question of this lesson: Why do elements form compounds? Evaluate 1- Determine the ions formed from strontium (Sr), aluminum (Al) and sulfur (S) 2- What ion will form when fluorine (F) reacts? What is the name of this ion? Explain Check your progress Check your progress Quiz 1. What is true of a chemical bond? A It is the force that holds two atoms together. B It is never formed by ions. C It is formed only by ions. D It forms by the attraction between the positive nucleus of one atom and the positive nucleus of another atom. CORRECT Quiz 2. Which best describes why atoms try to form an arrangement of eight valence electrons in their outer energy level? A to gain electrons B to lose electrons C to form ions D to acquire the stable electron structure of a CORRECT noble gas Quiz 3. Which of the following is true? A Anions are positively charged ions. B A chloride ion is a cation. C A sodium ion is an anion. D Cations are positively charge ions. CORRECT Quiz 4. Which metals are the most reactive? A metals in groups 1 and 3 B metals in groups 1 and 2 C metals in groups 2 and 13 D Metals are not reactive. CORRECT Quiz 5. Which letter on the graph represents the zone of physiological stress? A They are not reactive. B They all have noble gas configurations. C They are found on the left side of the periodic table. They easily gain electrons to attain a CORRECT stable outer electron configuration. D lesson 2: Ionic Bonds and Ionic Compounds BP:173 Focus Question How are the ions in ionic compounds arranged? New Vocabulary ionic bond ionic compound crystal lattice Electrolyte lattice energy Review Vocabulary compound: a chemical combination of two or more different elements Engage: Formation of an Ionic Bond Formation of an Ionic Bond - The electrostatic force that holds oppositely charged particles together in an ionic compound is referred to as an ionic bond. - Compounds that contain ionic bonds are ionic compounds Formation of an Ionic Bond - If ionic bonds occur between metals and the non metal oxygen, oxides form. - Most other ionic compounds are called salts Explore and explain: Formation of an Ionic Bond -Sodium and chlorine react vigorously, forming the common ionic compound table salt. -During this reaction, a sodium atom transfers its valence electron to a chlorine atom and becomes a positive ion. The chlorine atom accepts the electron into its outer energy level and becomes negative ion - The oppositely charged ions attract each other, forming the compound sodium chloride Explore and explain: Formation of an Ionic Bond Magnesium and oxygen react to produce the ionic compound magnesium oxide, which has uses in environmental remediation Explore and explain: Formation of an Ionic Bond Aluminum and bromine also release a good deal of energy when they react, producing the ionic compound aluminum bromide Formation of an Ionic Bond: Binary ionic compounds • Binary means that the compounds contain only two different elements. • Binary ionic compounds contain a metallic cation and a nonmetallic anion. • Sodium chloride (NaCl) is a binary compound. Formation of an Ionic Bond: Binary ionic compounds What role does ionic charge play in the formation of ionic compounds? Formation of an Ionic Bond: Binary ionic compounds - What role does ionic charge play in the formation of ionic compounds? Ionic compounds are electrically neutral and the number of electrons lost and gained must be equal consider how calcium Fluoride forms: Calcium needs to lose two electrons and Fluorine must gain 1 electron. The number of electrons lost and gained must be equal SO two fluorine atoms are needed to accept the two electrons lost from calcium atom Formation of an Ionic Bond: Binary ionic compounds Properties of Ionic Compounds Electrical forces in ionic bonds produce unique physical structures. - Physical structures: The ions are packed into a repeating pattern that balances the forces of attraction and repulsion between the ions. Properties of Ionic Compounds • The strong attractions among the positive ions and the negative ions in an ionic compound result in the formation of a crystal lattice. • A crystal lattice is a three-dimensional geometric arrangement of particles. Properties of Ionic Compounds Physical properties • Melting point, boiling point, and hardness are physical properties. They are determined by the strength of electrical forces between particles in matter. • Ionic bonds are relatively strong, so ionic crystals require a lot of energy to be broken apart. Thus, the crystals have high melting and boiling points. Properties of Ionic Compounds Properties of Ionic Compounds • • Ionic crystals are hard, rigid, brittle solids due to the strong attraction between electric charges that hold the ions in place. This figure shows how and why crystals break when a force strong enough to overcome these attractive forces is applied. Properties of Ionic Compounds • The ability of a material to conduct electricity depends on the availability of freely moving charged particles, so whether they are free to move determines whether an ionic compound conducts electricity. • In a solid, ions are locked in position by strong attractive forces. Thus, ionic solids are poor conductors. • In ionic compounds in solution or a liquid state, ions are free to move. Thus, these compounds conduct electricity. • An ionic compound whose aqueous solution conducts an electric current is called an electrolyte. Energy and the Ionic Bond • During a chemical reaction, energy is either absorbed or released. • Reactions that absorb energy are endothermic. • Reactions that release energy are exothermic. Energy and the Ionic Bond • The formation of ionic compounds from positive ions and negative ions is always exothermic. • The attraction of the ions forms a more stable system that is lower in energy than the individual ions. Energy and the Ionic Bond • Because ions in ionic compound are arranged in crystal lattice, the energy required to separate 1 mol of ions of an ionic compound is the lattice energy. • The strength of the electrical forces holding ions in place is reflected by the lattice energy. • The greater the lattice energy, the stronger the force of attraction. Energy and the Ionic Bond • • • Lattice energy is related to ion size. The electrostatic force of attraction between opposite charges increases as the distance between the charges decreases. Smaller ions form compounds with more closely spaced ionic charges, so they have stronger attractions and greater lattice energies. Explain:Energy and the Ionic Bond Explain the relationship between lattice energy and the size of ions in an ionic compound Energy and the Ionic Bond - The value of lattice energy is also affected by the charge of the ion. - The ionic bond formed from the attraction of ions with larger positive or negative charges generally has a greater lattice energy https://quizizz.com/admin/quiz/623b54728e401b 001d74c865?source=quiz_share Energy and the Ionic Bond 1- Notice the lattice energy of SrCl2 and AgCl. How do they show the relationship between lattice energy and charge of ions involved? Elaborate Answer the focus question of this lesson: How are the ions in ionic compounds arranged? Evaluate 1- Determine the ionic compound formed from Mg and Cl. Explain the formation 2- Using aluminum and oxygen, determine the formula of ionic compound formed . Quiz 1. Which of the following is not an ionic compound? A magnesium oxide B sodium chloride C water D barium sulfate CORRECT Quiz 2. Identify the binary ionic compound. A H2O C NaCl B C6H12O6 D Be3Al2Si6O18 CORRECT Quiz 3. What term best describes the structure formed by the strong attractions among the positive ions and the negative ions in an ionic compound? A a mineral B an oxide C a salt crystal D a crystal lattice CORRECT Quiz 4. Which of the following is true of ionic crystals? C Ionic bonds are strong, so ionic crystals require a large amount of energy to be broken. CORRECT Ionic crystals have low melting points and high boiling points. Ionic crystals are malleable, not brittle. D Ionic crystals always conduct electricity. A B Quiz 5. Which of the following is correct? A B C D Lattice energy is the energy needed for 1 mol of positive ions to bond with 1 mol of negative ions. Ions in an ionic compound are arranged in a random pattern. Ionic compounds are never electrolytes. Ionic compound properties are related to ionic bonding. CORRECT