chemical bonding: ch. 8 or, what atoms will do to achieve a noble gas configuration (stable octet)

Chemical Bonding: Ch. 8

Or, what atoms will do to achieve a noble gas configuration (stable

octet).

Two ways atoms can achieve Two ways atoms can achieve stabilitystability

Lose or Gain electrons:Lose or Gain electrons:Na Na +1+1 (loses 1 electron) Cation (loses 1 electron) CationCl Cl -1-1 (gains 1 electron) Anion (gains 1 electron) Anion

Then the oppositely charged ions attract and Then the oppositely charged ions attract and you get what’s called an you get what’s called an IONIC BONDIONIC BOND..

Other examples: KCl MgO MgClOther examples: KCl MgO MgCl22

Composed of a Composed of a MetalMetal & & Non-metalNon-metal !! !!

Another way is to “share” electrons

Bonds created by sharing are called:Covalent Bonds

The electronegativity of the atoms is not strong enough to take an electron (can’t pay the ionization energy).

Examples: HCl H2O CO2

Composed of two or more Non-metals !!

Properties of Ionic BondsProperties of Ionic Bonds The stronger of the two. How do we The stronger of the two. How do we

know? Melting Pt. of NaCl = 801 know? Melting Pt. of NaCl = 801 ooCC Boiling Pt. of HBoiling Pt. of H220 = 100 0 = 100 ooCC

Responsible for all the crystals in the Responsible for all the crystals in the world, p. 218.world, p. 218.

They form very organized shapes called They form very organized shapes called LatticesLattices. The energy to break up the . The energy to break up the Lattice is the Lattice is the Lattice EnergyLattice Energy..

Here’s a good Deductive Question. Page 220 Why is the Lattice Energy for

NaCl (769) less than MgO (3795)?

Na+Cl- vs. Mg 2+O2-

MgO has the greater +/- attraction! Oh, I get it !!

Ionically bonded compounds dissolve in water nicely. Solutions: homogenous mixtures Ionic compounds like NaCl dissolve in

water and create solutions called: ELECTROLYTES Electrolytes are solutions that conduct electricity !!

Let’s see.

Let’s see if you can answer this!!Let’s see if you can answer this!!

Why is the Melting Point for the Why is the Melting Point for the compound compound KFKF (858 (858 ooC) greater than C) greater than that of that of KIKI (681 (681ooC).C).

Answer:Answer:What is common between them?What is common between them?The valence electron for The valence electron for FF is in is in

level level 22; for ; for II, it’s level , it’s level 55 (farther (farther away and easier to break the away and easier to break the bond!).bond!).

Now, how do you Now, how do you writewrite and and namename formulas for formulas for IonicIonic

compounds?compounds?1.1. NaClNaCl sodium chloridesodium chloride2.2. MgOMgO magnesium oxidemagnesium oxide3.3. CaCa33(PO(PO44))22 calcium phosphatecalcium phosphate

Here’s the system. We want to be able Here’s the system. We want to be able to to writewrite a formula for a compound, a formula for a compound, and then and then namename it. And, we want to it. And, we want to be able to write a formula be able to write a formula fromfrom the the name of a compound.name of a compound.

Two kinds of Ionic Two kinds of Ionic compoundscompounds

BiBinary ionic: made of 2 elements!nary ionic: made of 2 elements! Ternary ionic: made of 3 or more!Ternary ionic: made of 3 or more!

Examples:Examples:NaClNaCl MgOMgO

CaCa33(PO(PO44))22

binarybinary binarybinary ternaryternary

BinaryBinary First write the correct formula by First write the correct formula by

balancing the ionic charges!balancing the ionic charges!

NaNa+1+1 + Cl + Cl-1-1 NaClNaClCaCa+2+2 + S + S-2-2 CaS CaSAlAl+3+3 + O + O-2-2 Al Al22OO33

Write the NameWrite the Name TwoTwo Words Words Write the name of the Write the name of the CationCation first first

(always!)(always!) Write the “root” of the Write the “root” of the AnionAnion

oxygen is oxygen is oxox; chlorine is ; chlorine is chlorchlor . . . . . . End the anion name with the suffix – End the anion name with the suffix –

ideide ExEx: NaCl is sodium chloride !: NaCl is sodium chloride !

Try these !Try these !Write the correct formula and Write the correct formula and

namename Li + O Li + O Ca + F Ca + F K + Cl K + Cl

LiLi22O = lithium oxideO = lithium oxideCaFCaF22 = calcium fluoride = calcium fluorideKCl = potassium chlorideKCl = potassium chloride

Let’s go from the name to the formula! Barium sulfide Copper(II)chloride Iron(III)oxide

What’s with the Roman Numeral stuff??BaS CuCl2 Fe2O3

Can you figure it out based on the formula??

The “transition elements” have more than one possible charge. So, how do we know if Fe (iron) is +2 or +3 Answer: the Roman Numeral Old system for these multivalence elements

was Fe+2 = ferrous & Fe+3 = ferric Sn +2 = stannous & Sn+4 = stannic Don’t panic! The Roman Numeral makes

it much easier. Iron(II) means Fe+2

Let’s try that again!

Copper(II)chloride Zinc fluoride Tin(IV)oxide

CuCl2 ZnF2

SnO2

Do the following on a sheet of paper: Write the Name1. Li + Br2. Ag + Cl3. Mg + S4. Ca + Se5. K + Ar6. Fe(III) + S

Write the Formula1. Cesium bromide2. Chromium(III) sulfide3. Lithium iodide4. Barium phosphide5. Aluminum nitride6. Boron oxide