Chemical Bonds

Chapter 52 Ions Ions have different numbers of electrons and protons Cations have lost electrons and have net positive charge Anions have gained electrons and have net negative charge

Chapter 53 Chemical Bonds Force of Attraction between any two atoms in a compound Involve VALENCE electrons Related to shape of molecule Related to chemical and physical properties of materials

Chapter 54 Types of Bonds Ionic Bond Electrostatic attraction between positive and negative ions. Involves transfer of electrons from one atom to another Covalent bond Two atoms share a pair of electrons.

Chapter 55 Definitions Valence electrons – outermost level with electrons Core electrons – all other electrons in an atom Isoelectronic – same number of electrons

Chapter 56 Octet Rule Most stable situation is full octet of electrons in outermost energy level –Exception: H and He need only 2 electrons Atoms gain, lose or share electrons to achieve this octet (noble gas arrangement) This changing of electrons involves a reaction

Chapter 57 Lewis Symbols Also called Lewis Dot or Electron Dot Way of depicting Valence Electrons around an atom (s and p electrons in highest energy level) Show valence electrons as “dots”

Chapter 58 Lewis Single Atom The number of dots is equal to the number of: –valence electrons –outermost energy level electrons –outermost shell electrons –Group number (main groups only)

Chapter 59 Lewis Symbol for single atom Show atomic symbol Show valence electrons as “dots” Li Mg

Chapter 510 Lewis Symbols

Chapter 511 Electron-Dot Structures

Chapter 512 Write the Lewis structure for: Mg C Ar I Rb P

Chapter 513.

Chapter 514 Lewis Dot Symbol for Ions Electrons are gained or lost to form full octet

Chapter 515 Cations (Positive Ions) Groups IA, IIA, IIIA form ions by removing the electrons in the outermost shell This is generally the group number of electrons Ca group IIA lose 2 e - Ca 2+ Na group IA lose 1 e - Na +

Chapter 516

Chapter 517 Anions (Negative Ions) Groups VA, VIA, VIIA form ions by adding electrons to the outermost shell to make full octet This is the number of electrons that when added to the group number give eight N group VA add 3 e - N 3- Cl group VIIA add 1 e - Cl -

Chapter 518

Chapter 519 What ion is formed from: F Mg O Cs Ba P Ar

Chapter 520.

Chapter 521 Generally, metals in groups IA, IIA and IIIA react with nonmetals in groups VA, VIA and VIIA to form ionic compounds

Chapter Form positive ion by removing electrons from a group A metal 2.Form negative ion by adding electrons to form a full octet 3.Write the formula for the ionic compound formed (smallest ratio of ions to give neutral compound)

Chapter 523 Reaction of Sodium with Chlorine Sodium—Soft grayish metal Chlorine—pale yellow-green gas (poisonous) Sodium Chloride—White crystalline solid (Table salt)

Chapter 524 Reaction of Sodium with Chlorine Chlorine gains electron from sodium

Chapter 525 Ionic Bonding in NaCl Form Na + and Cl - ions Opposite charges attract each other Organize themselves in orderly arrangement (crystal)

Chapter 526

Chapter 527 Do not have “pairs” of Na + and Cl - ions paired up with each other Each Cl - is “associated” with 6 Na + ions Each Na + is “associated with 6 Cl - ions Formula unit: lowest ratio of ions that form compound

Chapter 528 Ionic Compounds Writing Formula Naming Compound (Nomenclature)

Chapter 529 Combining Ions to Make Compounds Compound must be neutral positive charges = negative charges net charge = 0

Chapter 530 To write formula: Need correct number of each ion to give neutral compound Na + and Cl - (+1) + (-1) = 0 NaCl Na + and S 2- (+1) + (-2) = 2Na + and S 2- 2(+1) + (-2) = 0 Na 2 S(indicate 2 Na + with subscript)

Chapter 531 The formulas of ionic compounds are determined from the charges on the ions. atoms ions     – Na  +  F :  Na + : F :  NaF     sodium fluorine sodium fluoride The overall charge of NaF is zero (0). (1+ ) + (1-) = 0 Ionic Formulas: Sodium Fluoride

Chapter 532 Sodium Chloride

Chapter 533 MgCl 2 Ions with 2+ and -1 charges

Chapter 534 More Ionic Compounds

Chapter 535 Binary Ionic Compounds Only two elements in compound

Chapter 536 Write formula for compound made from : Mg 2+ and S 2- Al 3+ and Cl - Mg 2+ and P 3-

Chapter 537 Write formula for compound made from : Mg 2+ and S 2- MgS Al 3+ and Cl - AlCl 3 Mg 2+ and P 3- Mg 3 P 2

Chapter 538 Naming Ionic Compounds Name of positive ion first Name of negative ion second Do not need to indicate how many of each ion is in compound Need to know how to name ions first

Chapter 539 Naming Ions For cations, simple positive ions –Add the word ion to element name –Examples:Na + – sodium ion Al 3+ – aluminum ion For anions, simple negative ions –Change the usual element ending to -ide –Examples:Cl – – chloride S 2– – sulfide

Chapter 540 Common Ions (from single atoms)

Chapter 541

Chapter 542 Polyatomic Ions Groups of atoms that combine and have an overall charge NH 4 + ammonium ion OH - hydroxide ion

Chapter 543 Table 4.3

Chapter 544 Naming Ionic Compounds 1.Name positive ion first 2.Name negative ion second Note: Do not need to show how many ions are in formula

Chapter 545 Naming Ionic compounds MgS AlCl 3 Mg 3 P 2

Chapter 546 Naming Ionic compounds MgSMagnesium Sulfide AlCl 3 Aluminum Chloride Mg 3 P 2 Magnesium Phosphide Note: Number of ions not in name

Chapter 547 Compounds with Polyatomic Ion Mg 2+ NO 3 - Mg(NO 3 ) 2 magnesium nitrate Use parentheses to show that there are two nitrate ions

Chapter 548 Octet Rule Atoms tend to gain or lose electrons to reach more stable octet arrangement Octet has eight valence electrons (H has only two) Full octet same as noble gas valence shell

Chapter 549 Ionic vs Covalent Compounds Ionic: –held together by charges on ions –Contain a metal and a nonmetal Covalent: –held together by shared electrons –Contain two non-metals

Chapter 550 Covalent Compounds Contain only covalent bonds (share electron pairs to complete octet) Rules for naming covalent (molecular) compounds DIFFERENT than rules for naming ionic compounds

Chapter 551 What kind of compound is it? Ionic or Covalent For compounds with only TWO elements: An ionic compound contains one metal and one non-metal A covalent compound contains two non- metals

Chapter 552 Ionic or Covalent? CaO N 2 O H 2 S H 2 O MgCl 2 IF 3 CS 2 Na 2 O

Chapter 553 Naming covalent compounds Name each element in order it appears in compound For second element, use stem + “ide” Use prefix to indicate number of atoms of each element (mono if only one atom is present) Final vowel in prefix may be dropped if element begins with a vowel

Chapter 554 Naming Covalent Compounds Use prefixes to show number of each type of atom

Chapter 555 Example NO 2 ( ) nitrogen ( ) oxide 2 O’snitrogen dioxide 1 NMononitrogen dioxide often omit “mono” Nitrogen dioxide

Chapter 556 Name the following: CCl 4 N 2 O 3 SiS 2

Chapter 557 Name the following: CCl 4 carbon tetrachloride N 2 O 3 dinitrogen trioxide SiS 2 silicon disulfide

Chapter 558 Write the formula for dihydrogen monoxide Silicon tetrafluoride dinitrogentetroxide

Chapter 559 Write the formula for dihydrogen monoxideH 2 O Silicon tetrafluorideSiF 4 dinitrogentetroxideN 2 O 4

Chapter 560 Covalent Compounds Contain only covalent bonds (share electron pairs to complete octet) Rules for naming covalent (molecular) compounds DIFFERENT than rules for naming ionic compounds

Chapter 561 Naming covalent compounds Name each element in order it appears in compound For second element, use stem + “ide” Use prefix to indicate number of atoms of each element (mono if only one atom is present) Final vowel in prefix may be dropped if element begins with a vowel

Chapter 562 Table 4.4