Physical Science II
Physical Science II SCI 3120
Popular in Course
TPSYCH 409 A
verified elite notetaker
Popular in Science
Mrs. Clemens Smitham
verified elite notetaker
This 4 page Class Notes was uploaded by Mrs. Clemens Smitham on Monday October 5, 2015. The Class Notes belongs to SCI 3120 at Clayton State University taught by Harold Banke in Fall. Since its upload, it has received 33 views. For similar materials see /class/219550/sci-3120-clayton-state-university in Science at Clayton State University.
Reviews for Physical Science II
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/05/15
Chapter 23 Chemical Bonding This chapter deals with the electrical forces holding atoms together in compounds The attraction among atoms in compounds is called a chemical m There are 3 basic types metallic ionic and covalent This chapter deals with ionic and covalent bonds but we will look brie y at metallic bonds as well Metallic bonds In metals the outer electrons are weakly held to the nuclei These electrons are easily dislodged leaving behind positively charged metal ions REVIEW ions The positive ions tend to remain in a fixed position within the metal while the outer electrons flow freely through the resulting assembly of ion The electrons act like a m that all of the positive ions are attracted to The attraction between the electron uid and the positive ions holds the metal together and constitutes the metallic bond This particular type of bond accounts for most of the properties of metals The fact that the positive ions are attracted to the electrons from any position and any angle accounts for the fact that a metal can be pounded into sheets and still stay together This is the property of malleability Similar reasoning explains ductility Metals conduct electricity and heat Why Metals are opaque and shiny When a light wave strikes a metal it causes the mobile electrons to vibrate thus emitting EMR Mixtures of metal atoms can be held together just as well as atoms of the same element A mixture of metal atoms is called an M For example if gold is melted and mixed with melted palladium the resulting mixture of atoms is held together by the metallic bond The mixture is called white gold Sterling silver is a mixture of 925 Ag and 75 Cu An alloy of mercury is called an amalgam A dental lling is an amalgam of 70 Ag 10 Cu 18 Sn and 2 Hg Steel is an alloy of 97 Fe 2 Mn and 1 C Stainless steel is an alloy containing 18 Cr Aluminum cans are actually alloys of Al Zn and Mn Chemical Bonding The ability of atoms to bond together is determined by the arrangement of valence electrons those in the outermost energy level The valence shell may be symbolized by the electrondot structure shown in an electrondot diagram This diagram shows the 2 sublevels of the valence shell The first sublevel called the s sublevel contains a maximum of 2 electrons in one pair The second sublevel called the p sublevel contains a maximum of 6 electrons in 3 possible pairs Thus the valence shell contains a maximum of 8 electrons in 4 possible pairs Disregard the diagram of Krypton page 389 See bottom of page 389 Paired electrons are relatively stable and usually do not participate in bonding Unpaired electrons strongly tend to bond Each unbonded electron represents a possible future chemical bond Thus hydrogen and uorine can form 1 bond While nitrogen can form 3 bonds and oxygen 2 bonds Bonds form through electron behavior and the key rule states Atoms tend to lose or gain electrons so that they end up with an outermost occupied shell that is lled to capacim Ionic bonds If metal atoms are in the presence of nonmetals they tend to lose their valence electrons to the nonmetals The metals become positive ions cations and the nonmetals become negative ions anions The oppositely charged ions attract each other and stick together with an ionic bond A compound held together by an ionic bond is called an ionic compound NaCl KI NaF are EXAIVIPLES Generally ionic bonds form between atoms from the left and right sides of the periodic table Members of each group tend to gain or lose the same number of electrons We represent the resulting ions with the atomic symbol and a superscript EX Ca2 or Ca 2 The number of electrons an atom gains or loses is called its valence Valence is used to determine the formulas of compounds EXAIVIPLE Ca and F Al and O In ionic compounds the formula tells us the relative numbers of atoms in a compound The atoms themselves or the ions are arranged in very specific arrays based on the size of the ions and their charges These arrays are called the cmstalline lattice and this microscopic regularity leads to a macroscopic regularity which we call cmstals Covalent bonds Imagine 2 children playing together and sharing toys A force that keeps them together is their mutual attraction for the toys they share In a similar way 2 atoms can be held together by their mutual attraction for a pair of electrons Hydrogen needs 2 electrons in its outer energy level to fill the level If 2 hydrogen atoms are near each other each hydrogen nucleus is attracted to its own electron as well as the other hydrogen s electron The 2 atoms then sh a pair of electrons and in so doing they form a covalent bond Hydrogen is a diatomic element because it is most stable when a pair of shared electrons fills its outer energy level 2 or more different elements joined by a covalent bond form a covalent compound Hydrogen and the nonmetals on the upper right of the periodic table have the strongest electron affinities and are eager to pull electrons from each other but usually are able only to share since they cannot pull the electrons away to form ionic bonds Oxygen has 6 electrons in its outer shell so it needs 2 more to complete the shell It has a strong electron affinity so it sometimes pulls 2 away from metals When it is near nonmetals it is able to share 2 pairs of electrons thus forming 2 covalent bonds Nitrogen can form 3 bonds and carbon can form 4 bonds If an oxygen atom is near other oxygen atoms the atoms share 2 pairs with each other and form 2 bonds between 2 atoms thus they form a double m Nitrogen is also diatomic but it forms triple bonds between the atoms Perhaps carbon could form a quadruple bond but there is no evidence that it does A structure formed by atoms that are bound together by covalent bonds is called a molecule Thus a molecule is the smallest unit of a covalent compound A molecule is too small to be seen but a covalent cmstal is visible to the naked eye In a covalent crystal the atoms are held in an array by covalent bonds instead of ionic bonds This makes a stronger structure and some covalent crystals such as diamond are very hard Covalent bond polarity If two atoms of the same element form a covalent bond they share the pair of electrons evenly If atoms from 2 different elements form a covalent bond they usually share unevenly and the pair of electrons are closer to one atom or spend more time around the atom This creates a partial negative charge near the atom with the greater attraction for the pair A partial positive charge is found near the other atom This molecule thus has electrical polarity and contains a dipole a separation of charges SYMBOLS p 401 8 8 A dipole is usually found along with a polar bond A molecule in which the bonding atoms share equally in the shared electron pair has a nonpolar bond We can predict whether a bond is polar or nonpolar by looking at the electronegatiVity of the atoms involved Electronegativity is related to electron affinity but it applies speci cally to the strength of an atom s pull on a bonding electrons DIAGRAM p 402 Generally the greater the difference in electronegativity between 2 atoms the greater the polarity of the bond When the difference is more than 17 the character of the bond becomes m There is no strict boundary between covalent and ionic DIAGRAM p 403 Molecular polarity If a molecule contains nonpolar bonds the entire molecule will be nonpolar But if the molecule contains polar bonds it might be polar as a whole In HCl the bond is polar and the molecule is also polar The bond between C and O is polar but in C02 the molecule is nonpolar because the bonding electrons are evenly distributed DRAW Likewise BF3 An important 1 molecule is water DRAW Polar molecules behave differently from nonpolar molecules One obvious difference is in boiling point If water were not polar there would be very little liquid water on Earth today and there would be m life as we know it
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'