Chemistry - Chemical Bonding - Quick Guides

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Study GuideChemistry–Chemical Bonding1.Covalent Bonds1.1What Makes Atoms Stable?Atoms are most stable when their outermost electron shell is full.This means:•Thes-subshell is filled, and•Thep-subshell is also filled.Onlyfive elementsnaturally have completely filled valence shells. These are theinert (noble)gases, found in the far-right column of the periodic table. Because their electron shells are alreadyfull, theydo not usually reactwith other elements.All other elements arenot stable on their own. To become stable, their atoms must eithergain,lose, or share electrons.1.2How Atoms Become StableMost atoms reach stability bysharing electrons with other atoms.This type of sharing forms acovalent bond.Scientists often useLewis diagramsto show this process. In these diagrams:•Eachvalence electronis shown as adot•Only theouter-shell electronsare drawn

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Study GuideExample: Fluorine AtomsFluorine is element number 9.Its electron configuration is:1s² 2s² 2p⁵This means:•It has7 valence electrons•It needs1 more electronto become stableEach fluorine atom has one unpaired electron. Whentwo fluorine atoms come close, they canshare one electron each.Together:

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Study Guide•Each atom now has8 electrons•The shared pair forms acovalent bond•The molecule formed isF₂There are14 electrons total, with each atom contributing 7.1.3Counting Valence ElectronsYou can find the number of valence electrons bycounting columnsin the periodic table (for main-group elements).For example:•Phosphorushas5 valence electrons•Chlorinehas7 valence electronsFigure 3. Counting valence electrons.1.4Forming the PCl₃MoleculePhosphorus needs3 more electronsto complete its outer shell.Each chlorine needs1 electron.So:•One phosphorus atom bonds with three chlorine atoms•Six electrons are sharedin total

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Study GuideImportant points:•All atoms now have8 valence electrons•6 electrons are shared•20 electrons remain unshared•Phosphorus contributes3 electrons•Each chlorine contributes1 electron1.5Structural FormulasChemists often simplify Lewis diagrams by usinglines instead of dots.•One line = one shared pair of electrons•This drawing is called astructural formula•Nonbonding electrons are sometimes omitted for clarity1.6Hydrogen Chloride (HCl)Hydrogen is different from most elements:•It only needs2 electronsto fill its shellIn hydrogen chloride:•Hydrogen shares1 electron•Chlorine shares1 electron

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Study Guide•Both atoms become stableIn the molecule:•Hydrogen has2 electrons•Chlorine has8 electrons1.7Double BondsSometimes atoms sharemore than one pair of electrons.Inethylene (C₂H₄):•Two carbon atoms sharefour electrons•This formstwo shared pairsBecause:•One shared pair = one covalent bond•Two shared pairs = adouble bondThis is shown usingtwo linesbetween atoms.1.8Triple BondsSome molecules sharethree pairs of electrons.In thenitrogen molecule (N₂):

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Study Guide•Each nitrogen atom has5 valence electrons•Six electrons are shared•Four electrons are nonbondingFigure 8.A double bond between two carbon atoms.Figure 9.A triple bond between two nitrogen atoms.Thethree shared pairsform atriple bond, shown asthree lines.2. Quiz: Covalent Bonds1. QuestionThe electrons involved in bonding areAnswer Choices•found closest to the nucleus•found in the nucleus•found in the highest occupied energy level(s)Correct Answerfound in the highest occupied energy level(s)Why This is Correct

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Study GuideElectrons that participate in chemical bonding are calledvalence electrons. These electrons arelocated in theoutermost (highest occupied) energy levelof an atom, where they can interact withelectrons from other atoms to form bonds.For ExampleIn a sodium atom, the single electron in the outermost shell is involved in bonding, not the electronsclose to the nucleus.2. QuestionAtoms in a molecule are held together byAnswer Choices•the strong nuclear force•chemical bonds•gravityCorrect Answerchemical bondsWhy This is CorrectAtoms in a molecule are connected bychemical bonds, which form when atoms share or transferelectrons. These bonds hold the atoms together in a stable arrangement.For ExampleIn a water molecule (H₂O), chemical bonds hold the hydrogen and oxygen atoms together, allowingthe molecule to exist as a single substance.3. QuestionWhen atoms share valence electrons, a(n) __________ is formed.

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Study GuideAnswer Choices•covalent bond•ionic bond•metallic bondCorrect Answercovalent bondWhy This is CorrectAcovalent bondforms when atomsshare valence electronsso that each atom can achieve a morestable electron configuration. Ionic bonds involve electron transfer, and metallic bonds involve a “seaof electrons,” not sharing between specific atoms.For ExampleIn a water molecule (H₂O), hydrogen and oxygen atoms share electrons, forming covalent bonds.4.QuestionTypically, when two atoms form a chemical bond, the expected result is that the electronsAnswer Choices•will be in the excited state•will be completely removed from both atoms•will complete a noble gas configuration for both atomsCorrect Answerwill complete a noble gas configuration for both atomsWhy This is Correct

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Study GuideAtoms form chemical bonds in order to become more stable. By gaining, losing, or sharing electrons,atoms usually achieve anoble gas configuration, meaning a full outer energy level. This stablearrangement lowers the atom’s energy.For ExampleWhen sodium bonds with chlorine, sodium loses one electron and chlorine gains one, allowing bothatoms to achieve stable noble gas configurations.5. QuestionGenerally speaking, when two nonmetals form a chemical bond, the bond is a(n)Answer Choices•covalent bond•ionic bond•metallic bondCorrect Answercovalent bondWhy This is CorrectWhen two nonmetals bond, they tend toshare electronsrather than transfer them. This sharing ofelectrons forms acovalent bond. Ionic bonds usually occur between metals and nonmetals, andmetallic bonds occur between metal atoms only.For ExampleIn a water molecule (H₂O), hydrogen and oxygen are both nonmetals and share electrons, formingcovalent bonds.6.QuestionWhat type of diagram uses a single dot to represent an electron?

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Study GuideAnswer Choices•Dalton diagram•Thomson diagram•Lewis diagramCorrect AnswerLewis diagramWhy This is CorrectALewis diagramrepresentsvalence electronsasdotsaround the chemical symbol of an element.Each dot stands for one electron involved in bonding.For ExampleThe Lewis diagram of oxygen showssix dotsaround the symbolO, representing its six valenceelectrons.7.QuestionTypically, when forming a chemical bond, the goal is to achieve __________ electrons in theoutermost energy shell?Answer Choices•2•6•8Correct Answer8Why This is Correct

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