Compounds and their Bonds Ionic Bonds & Naming Ionic Compounds

REVIEW The group your element is in, determines the number of valence electrons How do you use the Periodic Table to determine the number of valence electrons for a given element?

REVIEW: Lewis Electron Dot Structure Symbols of atoms with dots to represent the valence-shell electrons 1A 2A 3A 4A 5A 6A 7A 8A H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar

LEARNING CHECK A. X would be the electron dot formula for 1) Na 2) S 3) Al   B.  X  would be the electron dot formula for  1) B 2) N 3) Cl

CHEMICAL BONDS: Why do atoms form bonds? Atoms are stable when they have 8 valence electrons They fulfill the Octet Rule There is always an exception: Hydrogen and Helium Hydrogen only needs one more electron to fill its valence shell Helium is full with its 2 valence electrons therefore does not bond Atoms can fulfill the Octet Rule when they gain, lose or share electrons

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons of lose 4 electrons Gain 3 electrons Gain 2 electrons

CHEMICAL BONDS: What types of bonds are there? Ionic Bonds Covalent Bonds Metallic Bonds Hydrogen Bonds

What is an ion? An ion: an atom or bonded group of atoms with a positive or negative charge Cation: A positively charged ion Anion: A negatively charged ion + -

IONIC BONDS Group 1A metals  ion 1+ Group 2A metals  ion 2+ Bonds formed between 2 ions by the transfer of electrons Result when a metal reacts with a non-metal Metals lose electrons (transfer e- to the non-metal) to match the number of valence electrons of their nearest noble gas Positive ions (CATIONS) form when the number of electrons are less than the number of protons Group 1A metals  ion 1+ Group 2A metals  ion 2+ Group 3A metals  ion 3+ + means it has more protons

LEARNING CHECK 1. Number of valence electrons in aluminum A) 1 e- B) 2 e- C) 3 e- 2. Change in electrons for octet A) lose 3e- B) gain 3 e- C) gain 5 e- 3. Ionic charge of aluminum A) 3- B) 5- C) 3+

SOLUTION 1. Number of valence electrons in aluminum C) 3 e- 2. Change in electrons for octet A) lose 3e- 3. Ionic charge of aluminum C) 3+

IONIC BONDS Non-metals in groups 5A, 6A, and 7A gain electrons from the metals Non-metals: Accept electrons from the metal Gain electrons Negative ions (ANIONS) form when the number of electrons is more than the number of protons Group 5A metals  ion 3- Group 6A metals  ion 2- Group 7A metals  ion 1- - Means less protons

LEARNING CHECK Number of valence electrons in Oxygen A) 5 e- B) 6 e- C) 7 e- Change in electrons for octet A) gain 2 e- B) lose 2 e- C)gain 4 e- Ionic charge for Oxygen A) 2+ B) +4 C) 2-

SOLUTION Number of valence electrons in Oxygen B) 6 e- 2. Change in electrons for octet A) gain 2 e- Ionic charge for Oxygen C) 2-

IONIC BONDS Properties High Melting point and Boiling Point Conductors of electricity Strong bonds; stronger than covalent bonds Bond by transfer electrons

REVIEW: IONIC BOND an electron is simply transferred to another atom. By doing so, each atom is able to have a stable valence shell. It is called an ionic bond because the atoms become ions, a charged atom that has either lost an electron (positive charge) or has gained an electron (negative charge). Below is an animation of ionic bonding:

WRITING IONIC COMPOUNDS Write each ion, cation first Don’t show charges in the final formula. Overall charge must equal zero. Use parentheses to show more than one polyatomic ion. Stock System – Roman numerals indicate the ion’s charge used when the ion has more than one oxidation state (Transition elements) Copyright © 2009 by Pearson Education, Inc.

Polyatomic ion NO3 goes in parentheses Calcium Nitrate Ca+2 NO3-1 Ca1(NO3)2 Ca (NO3)2 1(+2) + 2(-1)= 0 EXAMPLE: Cross the exponents only! not the + or - Do NOT show 1 in the final formula Polyatomic ion NO3 goes in parentheses This is your final formula! Check for the overall charge to equal zero

LEARNING CHECK potassium chloride magnesium nitrate copper(II) chloride K+ Cl-  KCl Mg2+ NO3-  Mg(NO3)2 Cu2+ Cl-  CuCl2

NAMING IONIC COMPOUNDS Identify the cation and anion Name the cation first Name the anion with an –ide ending

Learning Check Complete the names of the following ions: (Is it a cation or an anion?) Ba2+ Al3+ K+ _________ __________ _________ N3 O2 F _________ __________ _________

Solution Ba2+ Al3+ K+ barium aluminum potassium N3 O2 F nitride oxide fluoride

Examples of Ionic Compounds with Two Elements Formula Ions Name cation anion NaCl Na+ Cl- sodium chloride K2S K+ S2- potassium sulfide MgO Mg2+ O2- magnesium oxide CaI2 Ca2+ I- calcium iodide Al2O3 Al3+ O2- aluminum oxide

Learning Check Write the names of the following compounds: 1) CaO ___________ 2) KBr ___________ 3) Al2O3 ___________ 4) MgCl2 ___________

Solution Write the names of the following compounds: 1) CaO calcium oxide 2) KBr potassium bromide 3) Al2O3 aluminum oxide 4) MgCl2 magnesium chloride

Metals That Form More Than One Cation The name of metals with two or more positive ions (cations) use a Roman numeral to identify ionic charge.

Naming Ionic Compounds with Variable Charge Metals

Naming Variable Charge Metals Transition metals with two different ions use a Roman numeral after the name of the metal to indicate ionic charge.

EXAMPLE: Naming FeCl2 To name FeCl2: 1. Determine the charge of the cation using the subscript of the anion (Cl-). Fe ion = 2+ 2. Name the cation by the element name and add a Roman numeral in parentheses to show its charge. Fe2+ = iron (II) 3. Write the anion with an ide ending. FeCl2 = iron(II) chloride Remember Iron is a Transition metal which is the reason for the Roman numeral

Learning Check Select the correct name for each. 1. Fe2S3 A) iron sulfide B) iron(II) sulfide C) iron(III) sulfide 2. CuO A) copper oxide B) copper(I) oxide C) copper(II) oxide

Solution Select the correct name for each. A. Fe2S3 C) iron (III) sulfide Fe3+ S2- B. CuO C) copper (II) oxide Cu2+ O2-