Ionic and Covalent Bonding PDF

REVIEW Lesson 1Quantum Mechanical Description and the Electronic Structure of Atoms Section 1: The quantum numbers Section 2: Electronic configuration  Section 1: Ionic and Covalent Bonding Recitation Give example of ionic or covalent compound which is important in our every life ...

REVIEW Lesson 1Quantum Mechanical Description and the Electronic Structure of Atoms Section 1: The quantum numbers Section 2: Electronic configuration  Section 1: Ionic and Covalent Bonding Recitation Give example of ionic or covalent compound which is important in our every life  8 I want you to meet a friend of mine? Bonding, the way atoms are attracted to each other to form molecules, determines nearly all of the chemical properties we see. And, as we shall see, the number “8” is very important to chemical bonding.  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 5  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 6  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 7  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 8  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 9  Describing Ionic Bonds  An ionic bond is a chemical bond formed by the electrostatic attraction between positive and negative ions. – This type of bond involves the transfer of electrons from one atom (usually a metal) to another (usually a nonmetal). – GRAND SECRET OF CHEMISTRY……….??? All atoms want the same electron configuration as the noble gases! - As a result of electron transfer, the atom which gives up an electron becomes a positive ion, while the atom which accepts the electron become negative ion. - Ionic compounds conduct electricity when in solution but not in solid phase. - Ionic compounds are generally soluble in water and in polar solvents.  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 12 Describing Ionic Bonds  Such noble gas configurations and the corresponding ions are particularly stable. – The atom that loses the electron becomes a cation (positive). 1 - Na([Ne]3s ) Na ([Ne])  e  – The atom that gains the electron becomes an anion (negative). 2 5 - 2 6 Cl([Ne]3s 3p )  e Cl ([Ne]3s 3p )  Describing Ionic Bonds  Consider the transfer of valence electrons from a sodium atom to a chlorine atom. Na  Cl Na  Cl   e- – The resulting ions are electrostatically attracted to one another. – The attraction of these oppositely charged ions for one another is the ionic bond.  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 15 Electron Configurations of Ions  As metals lose electrons to form cations and establish a “noble gas” configuration, the electrons are lost from the valence shell first. – For example, magnesium generally loses two electrons from its 3s subshell to look like neon. 2 - Mg Mg ( 2 e ) [Ne]3s2 [Ne] Electron Configurations of Ions  Transition metals also lose electrons from the valence shell first, which is not the last subshell to fill according to the aufbau sequence. – For example, zinc generally loses two electrons from its 4s subshell to adopt a “pseudo”-noble gas configuration. 2 - Zn Zn ( 2 e ) [Ar]4s23d10 [Ar]3d10  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 18 Covalent Bonds  When two nonmetals bond, they often share electrons since they have similar attractions for them. This sharing of valence electrons is called the covalent bond. – These atoms will share sufficient numbers of electrons in order to achieve a noble gas electron configuration (that is, eight valence electrons).  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 20 Covalent Bonds  The tendency of atoms in a molecule to have eight electrons in their outer shell (two for hydrogen) is called the octet rule. H. +.H H H:  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 23 Lewis Structures  The shared electrons in H2 spend part of the time in the region around each atom. H H : – In this sense, each atom in H2 has a helium configuration. Lewis Structures  The formation of a bond between H and Cl to give an HCl molecule can be represented in a similar way.. +.Cl: : : : : : : H H Cl – Thus, hydrogen has two valence electrons about it (as in He) and Cl has eight valence electrons about it (as in Ar). Lewis Structures  Formulas such as these are referred to as Lewis electron-dot formulas or Lewis structures. bonding pair : : : : H Cl lone pair – An electron pair is either a bonding pair (shared between two atoms) or a lone pair (an electron pair that is not shared). Coordinate Covalent Bonds  When bonds form between atoms that both donate an electron, you have: A. +.B A B : – It is, however, possible that both electrons are donated by one of the atoms. This is called a coordinate covalent bond. A + :B A B : Multiple Bonds  In the molecules described so far, each of the bonds has been a single bond, that is, a covalent bond in which a single pair of electrons is shared. – It is possible to share more than one pair. A double bond involves the sharing of two pairs between atoms. H H H H C : :C or C C : : H H : : H H Multiple Bonds  Triple bonds are covalent bonds in which three pairs of electrons are shared between atoms. H : C C : H or H C C H ::: Covalent bonds -Covalent bond involves the sharing of electrons that results in the formation of covalent compound whose representative particle is molecule, as a whole, a molecule does not carry a charge. -covalent bonds may be polar or nonpolar  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 31  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 32  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 33 Polar Covalent Bonds  A polar covalent bond is one in which the bonding electrons spend more time near one of the two atoms involved. – When the atoms are alike, as in the H-H bond of H2 , the bonding electrons are shared equally (a nonpolar covalent bond). – When the two atoms are of different elements, the bonding electrons need not be shared equally, resulting in a “polar” bond. Polar Covalent Bonds  For example, the bond between carbon and oxygen in CO2 is considered polar because the shared electrons spend more time orbiting the oxygen atoms. O C O d+ : : : : d- d- – The result is a partial negative charge on the oxygens (denoted d-) and a partial positive charge on the carbon (denoted d+)  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 36  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 37  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 38 Polar Covalent Bonds  Electronegativity is a measure of the ability of an atom in a molecule to draw bonding electrons to itself. – In general, electronegativity increases from the lower-left corner to the upper-right corner of the periodic table. – The current electronegativity scale, developed by Linus Pauling, assigns a value of 4.0 to fluorine and a value of 0.7 to cesium. 9_12 Electronegativities H 2.1 IA IIA IIIA IVA VA VIA VIIA Li Be B C N O F 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Na Mg VIIIB Al Si P S Cl 0.9 1.2 IIIB IVB VB VIB VIIB IB IIB 1.5 1.8 2.1 2.5 3.0 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br 0.8 1.0 1.3 1.5 1.6 1.6 1.5 1.8 1.8 1.8 1.9 1.6 1.6 1.8 2.0 2.4 2.8 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I 0.8 1.0 1.2 1.4 1.6 1.8 1.9 2.2 2.2 2.2 1.9 1.7 1.7 1.8 1.9 2.1 2.5 Cs Ba La–Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At 0.7 0.9 1.1–1.2 1.3 1.5 1.7 1.9 2.2 2.2 2.2 2.4 1.9 1.8 1.8 1.9 2.0 2.2 Fr Ra Ac–No 0.7 0.9 1.1–1.7 Polar Covalent Bonds  The absolute value of the difference in electronegativity of two bonded atoms gives a rough measure of the polarity of the bond. – When this difference is small (less than 0.5), the bond is nonpolar. – When this difference is large (greater than 0.5), the bond is considered polar. – If the difference exceeds approximately 1.8, sharing of electrons is no longer possible and the bond becomes ionic.  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 42  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 43  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 44  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 45  Pr es en tat io n of Le ct ur e Ou tli ne s, Copyright © Houghton Mifflin 9– Company.All rights reserved. 46  Activity 1 Bonding by Transfer of Electrons 1. What kind of element forms cation after ionic bonding? 2. What kind of element forms anion after ionic bonding? 3. Why do ions forms after ionic bonding? 4. How can you tell that ionic bonding will take place between metals and nonmetals? 5. Will all combinations of metals and nonmetals form ionic bond? Why? Why not?  Activity 2: Bonding by Sharing of Electrons Complete the table: Types of Covalent Bonds Compound Chemical Lewis Structure Type of Bond Formula (polar/nonpolar) ammonia water hydrogen chloride Pr nitrogen gas es en oxygen gas tat io n methane of Le hydrogen gas ct ur sulfur dioxide Ou e tli chlorine gas ne s, phosphine Copyright © Houghton Mifflin Company.All rights reserved. 9– 48  Follow up Questions: 1. How do covalent bonds form between atom? 2. What kinds of element usually forms covalent bond? 3. It is possible for metals and non-metals to form nonpolar bond? Why? why not? 4. Why is it diatomic molecules always form nonpolar covalent bonds? 5. Differentiate polar covalent bond from nonpolar covalent bond. Activity 3: What types of bond do you from?  Directions: Imagine yourself and the people around you as atoms. Just like atoms, you need to form bonds to be more stable. Your attitude, talents and potentials, love and care, advice and compliments, and the things you treasure should serve the function of electrons. Based on your understanding on the concept of ionic and covalent bonds, what type of bond do you want to form with other people? What do you want to do with your electrons? Support your answer. Your answer should not be less than 7 sentences and not more than 10 sentences. Chapter Assessment Goggle Classroom ePortfolio Sketch it!  Direction: On a short bond paper, draw a real-life scenario or situation in which the concept of ionic or covalent bonding is demonstrated or applied. Below your illustration, write at least five sentences describing your output and explaining how the situation is related to the concept of the type of chemical bond you chose. For example, you choose the concept of covalent bonding and you will draw a scene where two puppies are sharing a piece of bone and explain why the scenario is demonstrating the concept of covalent bonding.  Follow-up Question: (Write your answer at the back of your drawing)  ‘’What is the importance of chemical bonding in chemistry and in our life?’’ Section 2: Metallic Bonding