Chemical Bonding

Chemical Bonding Chapter 11

11.1: Electrons and Energy Levels • Have you ever stopped to consider that by using the 26 letters of the alphabet, you make all of the words you use every day? Although the number of letters is limited, you combine them in different ways to make a huge number of words. This is the same with elements. We combine them to make different substances.

11.1: Electrons and Energy Levels Combining Atoms Through Chemical Bonding • Chemical Bond - is the joining of atoms to form ionic compounds or molecules • The properties of these new substances are different than the properties of the original substance. • When chemical bonds form, electrons are • Lost • Gained • shared

11.1: Electrons and Energy Levels Electron number and organization • To understand how atoms form chemical bonds, you need to understand how electrons are arranged in an atom. • The number of electrons in an atom = the number of protons. • The number of protons can be determined by the atomic number. • The electrons are organized in energy levels. • 1st Energy Level: 2Diagram Fluorine: • 2nd Energy Level: 8 • 3rd Energy Level: 8

11.1: Electrons and Energy Levels

11.1: Electrons and Energy Levels Outer-Level Electrons and Bonding • Not all electrons in an atom take part in a bonding. • Most bonds form using the outer most electrons called valence electrons. • Valence electron - an electron in the outermost energy level of an atom.

11.1: Electrons and Energy Levels To bond or Not to Bond • Not all atoms bond the same way. • The number of valence electrons determines if an atom will form a bond. • Atoms want to be like noble gases (have a full outer shell of electrons). • 8 valence electrons • 2 valence electrons like He • Atoms bond by gaining, losing, or sharing electrons to have a full outer most energy level like the noble gases.

11.1: Electrons and Energy Levels Showing valence electrons used in bonding • Electron Dot Diagrams • models that represent valence electrons in an atom as dots around the element’s chemical symbol • Steps • Identify the element’s group number on the periodic table • Identify the number of valence electrons • Draw the electrons as dots (NESWNESW) • Determine if stable or how many bonds can form • Stable: All electrons are paired • Bonds possible: Each unpaired set of electrons

Draw electron dot diagrams for the valence electrons! • Stable elements? • 1 bond possible? • 2 bonds possible? • 3 bonds possible? • 4 bonds possible?

Complete with your partner • 1. How many valence electrons does C have? • 2. How many valence electrons does Ca have? • 3. How many valence electrons does S have? • 4. Why do elements form bonds?

11.2: Compounds, Chemical Formulas, and Covalent Bonds • Covalent Bonds are formed when two nonmetals share electrons. • Covalent Bond – a bond that forms when atoms share one or more pairs of electrons

11.2: Compounds, Chemical Formulas, and Covalent Bonds Covalent Compounds • Examples of covalent compounds: 1. ammonia 2. water 3. carbon dioxide • Properties 1.low melting points 2. low boiling points 3. Brittle as a solid • Substances containing covalent bonds consist of individual particles called molecules. • molecule - a neutral group of atoms that are joined together by one or more covalent bonds.

11.2: Compounds, Chemical Formulas, and Covalent Bonds Simple Covalent Compounds • When found in nature as pure elements, these seven elements exist only as two atoms covalently bonded. • H2 • O2 • N2 • Cl2 • Br2 • I2 • F2

11.2: Compounds, Chemical Formulas, and Covalent Bonds 1. Draw an electron dot diagram for each element 2. Combine the elements where they can share electrons so each have a full outer shell. (The shared electrons are the covalent bond) • Examples: • Hydrogen + Chlorine • Fluorine + Fluorine • Water • Oxygen + Oxygen

11.2: Compounds, Chemical Formulas, and Covalent Bonds • Draw the Lewis Structures (electron dot diagrams) for each of the following • CH4 CO2

Naming Covalent Compounds Prefixes One = mono Two = di Three = tri Four = tetra Five = penta Six = hexa Seven = hepta Eight= octa Nine = nona Ten = deca Rules: Prefix + namePrefix + name –ide Rule: Do NOT use mono- on the first element Examples: CO CO2 C2H4 P2O5 N3P6 11.2: Compounds, Chemical Formulas, and Covalent Bonds

11.3: Ionic and Metallic Bonds Ionic Compounds • Examples of ionic compounds: 1. table salt 2. deicer • Properties 1.high melting points 2. high boiling points Substances containing ionic bonds consist of individual particles called formula units. • Formula unit - a neutral group of atoms that are joined together by an ionic bond

11.3: Ionic and Metallic Bonds • An ionic bond is an attraction between positively and negatively charged ions in an ionic compound • Electrons are transferred • This creates ions, which are atoms that are no longer electrically neutral because they have gained or lost valence electrons • Ionic bonds form so that the outermost energy levels of the atoms in the bonds are full. • Ionic bonds form between a metal and a nonmetal Sodium Chlorine

11.3: Ionic and Metallic Bonds • Charged Particles • A transfer of electrons between atoms changes the number of electronsin each atom but the number of protonsstay the same. • The negative charges (electrons) and positive charges (protons) no longer cancel outand the atom becomes an ion. • Ion- an atom that gained or lost electrons

11.3: Ionic and Metallic Bonds • Charged Particles Continued • An atom cannot lose electrons without a nearby atom gaining electrons and visa versa. • Metals – tend to lose electrons and become a positive ion • cation

11.3: Ionic and Metallic Bonds • Charged Particles Continued • Nonmetals – tend to gain electrons and become a negativeion • anion • -ide- the ending that is given to atoms that gain electrons • Oxygen = __________ • Fluorine = __________ • Sulfur = __________

11.3: Ionic and Metallic Bonds Ionic Compounds • Metals tend to lose a certain number of electrons depending on their number of valence electrons and become positively charged • Nonmetals tend to gain a certain number of electrons depending on their number of valence electrons and become negatively charged IONIC CHARGES

11.3: Ionic and Metallic Bonds Ionic Compounds • When ionic bonds form, the number of electrons lost by the metal equals the number of electrons gain by the nonmetal atoms. • The ions that bond are charged but the compounds formed are neutral because the charges on the ions cancel out.

Complete with your partner • What types of elements form Ionic compounds? • Why?

11.3: Ionic and Metallic Bonds • Ionic Bonding Pictures • Draw the electron dot diagram for each element • Show the transfer of electrons from the metal to the nonmetal • Add more metal or nonmetal atoms until all elements have a full octet • Sodium Chlorine • Magnesium Fluorine

11.3: Ionic and Metallic Bonds Ionic Bonding Pictures • Lithium oxygen • Aluminum sulfur

11.3: Ionic and Metallic Bonds • Writing Formulas for Ionic Compounds ( metal + nonmetal) • Write the metal with its’ charge • Write the nonmetal with its’ charge • Criss- Cross the charges • Only bring down the #, NOT the charge • Examples: • Sodium and Chlorine • Barium and Chlorine • Potassium and Oxygen • Lithium and Sulfur

11.3: Ionic and Metallic Bonds • Write the formula for the ionic compound that forms: • 1. Potassium + Sulfur • 2. Magnesium + nitrogen • 3. Aluminum + phosphorous

11.3: Ionic and Metallic Bonds • Naming Ionic Compounds • Name of Metal + nonmetal w/ ending –ide • Examples: • Sodium and Chlorine • Barium and Fluorine • Potassium and Oxygen • Lithium and Sulfur

11.3: Ionic and Metallic Bonds • When ions bond, they form a repeating 3-dimensional pattern called a crystal lattice.

11.3: Ionic and Metallic Bonds • Properties of Metals 1. malleable 2. ductile 3. conduct heat/electric well • Metals are malleable and ductile because of the presence of a metallic bonds. • Metallic Bond – a bond between metals of the same atom

11.3: Ionic and Metallic Bonds Metallic Bonds • The positive ions in a metal form a lattice that is held in place by strong interactions between the positive ions and the surrounding electrons. • Sea of electrons or pool of electrons.

Complete on your own Write a paragraph about the 3 types of bonds and the types of elements that are involved in each.

Chemical Bonding