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On Your Best Behavior! Q1 • There are two types of atoms: Ionic Bonding – Reactive - interact with other elements. – Stable - Do not interact with other elements. Which of these atoms is reactive? Unit Essential Question: How does atomic structure determine the chemical and physical properties of matter? What information can be gathered from the periodic table? Presentation Objectives: § Define an ionic bond and ion. § Use Lewis structures to show how two elements ionically bond. It’s Bonding Time! Q2 • To become stable, form a chemical bond. – A force that holds elements together. • There are three main types of bonds that can form. – Covalent bonds • Atoms share valence electrons A “happy atom” is an atom with a completed outer shell Atoms prefer to have a completed outer shell. Can I Have That? Q3 • Atoms prefer to have a complete outer shell. – One way to accomplish this goal is to form an ionic bond. • Bond that forms when one atom gives up valence electrons and another takes them. – Ionic bonds • Atoms give up or take valence electrons – Metallic bonds • All the atoms in the metal share the valence electrons. They become ions, which are atoms with a charge! Q4 No Longer In Neutral Territory • Atoms in the periodic table are neutral. 35 Br – Number of protons equals the number of electrons. 79.904 • When an atom has only one or two valence electrons in its outer shell, it will give them away. – There are less electrons than protons • Let’s think about it mathematically… 35 – How many protons does Bromine (Br) have? • Protons are positively charged. Q5 What Happens When An Atom Loses An Electron? • Let’s say we have a sodium atom. + 35 – How many electrons does Bromine (Br) have? 35 P: 11 N: 12 Na Atom of Sodium Gives Away 1 VE Protons: + 11 Protons: + 11 Electrons: - 11 Electrons: - 10 0 • Electrons are negatively charged. - 35 +1 Because it has a positive charge, we have a positive ion, which is called a cation! Adding them together: (+ 35) + (- 35) = 0 Is Sodium Stable When It Loses An Electron? Q6 What Happens When An Atom Gains An Electron? • When an atom has six or seven valence electrons in its outer shell, it will take valence electrons. P: 11 N: 12 – There are more electrons than protons P: 11 N: 12 • Let’s say we have a chlorine atom. Atom of Chlorine Na Na +1 We leave the cation without electrons on the Lewis structure to show that it has emptied its outer ring. P: 17 N: 18 Cl Protons: + 17 Electrons: - 17 0 Takes 1 VE Protons: + 17 Electrons: - 18 -1 Because it has a negative charge, we have a negative ion, which is called an anion! Using Lewis Structures… Q7 • In ionic bonding, it is easy to represent what is happening using Lewis structures. • What ionic compound forms when Calcium (Ca) bonds with Fluorine (F)? – Use arrows to show where the electron goes! Na Cl Na+1 Cl -1 F Ca • The atoms that tend to give away their electrons are metals. – The atoms that accept the electrons are nonmetals. -1 F -1 Formula: CaF2 Now you can write the formula of NaCl the resulting compound! By convention, the cation is listed first! Q9 +2 Ca F F • Once the atoms give or take the valence electrons they become ions. Metals and Nonmetals Q8 Let’s Try Another One! Q10 Neutral in the End • When making ionic bonds, the ionic compound is neutral. – The charges of all the ions in the compound must add up to zero. +1 Na Cl -1 (+1) + (-1) = 0 +2 Ca F -1 F -1 (+2) + (-1) + (-1) = 0 This should help you check your work… Ionic bonds occur between a metal and a nonmetal. If they don’t add up to zero, there is a mistake that must be fixed!