WHY DO ATOMS BOND?

VALENCE ELECTRONS DETERMINE THE CHEMICAL PROPERTIES OF AN ELEMENT ELECTRONS IN THE OUTERMOST ORBITALS OF THE ATOM –GENERALLY THOSE ORBITALS ASSOCIATED HIGHEST ENERGY LEVEL DETERMINE THE CHEMICAL PROPERTIES OF AN ELEMENT ELECTRONS IN THE OUTERMOST ORBITALS OF THE ATOM –GENERALLY THOSE ORBITALS ASSOCIATED HIGHEST ENERGY LEVEL

VALENCE ELECTRONS THE OUTERMOST ELECTRONS ARE THE ONES MOST AFFECTED BY THE APPROACH OF ANOTHER ATOM. THE CORE ELECTRONS AND THE FILLED d SHELL ELECTRONS ARE NOT GREATLY AFFECTED BY REACTIONS WITH OTHER ATOMS,

VALENCE ELECTRONS LET’S EXAMINE SULFUR –EACH ATOM CONTAINS 16 ELECTRONS –SIX OF WHICH OCCUPY THE OUTERMOST 3-S AND 3P ORBITALS –EC: [Ne] 3s 2 3p 4 LET’S EXAMINE SULFUR –EACH ATOM CONTAINS 16 ELECTRONS –SIX OF WHICH OCCUPY THE OUTERMOST 3-S AND 3P ORBITALS –EC: [Ne] 3s 2 3p 4 SIMILARLY, ALTHOUGH CESIUM CONTAINS 55 ELECTRONS, IT ONLY HAS 1 VALENCE ELECTRON –[Xe] 6s 1 SIMILARLY, ALTHOUGH CESIUM CONTAINS 55 ELECTRONS, IT ONLY HAS 1 VALENCE ELECTRON –[Xe] 6s 1

ELECTRON-DOT STRUCTURES CHEMISTS OFTEN REPRESENT THE VALENCE ELECTRONS VISUALLY WITH A SIMPLE SHORTHAND METHOD –CONSISTS OF THE ELEMENT’S SYMBOL, REPRESENTS THE NUCLEUS AND THE CORE ELECTRONS –SURROUNDING THE SYMBOL ARE DOTS REPRESENTING THE ATOM’S VALENCE ELECTRONS CHEMISTS OFTEN REPRESENT THE VALENCE ELECTRONS VISUALLY WITH A SIMPLE SHORTHAND METHOD –CONSISTS OF THE ELEMENT’S SYMBOL, REPRESENTS THE NUCLEUS AND THE CORE ELECTRONS –SURROUNDING THE SYMBOL ARE DOTS REPRESENTING THE ATOM’S VALENCE ELECTRONS

ELECTRON-DOT STRUCTURES DOTS THAT REPRESENT VALENCE ELECTRONS, ARE PLACED ONE AT A TIME ON THE FOUR SIDES OF THE SYMBOL –THEY MAY BE PLACED IN ANY SEQUENCE –AND THEN PAIRED UP UNTIL ALL ARE USED –THE MAXIMUM NUMBER OF DOTS AROUND ANY GIVEN ELEMENT IS 8 DOTS THAT REPRESENT VALENCE ELECTRONS, ARE PLACED ONE AT A TIME ON THE FOUR SIDES OF THE SYMBOL –THEY MAY BE PLACED IN ANY SEQUENCE –AND THEN PAIRED UP UNTIL ALL ARE USED –THE MAXIMUM NUMBER OF DOTS AROUND ANY GIVEN ELEMENT IS 8

DOT STRUCT. ACROSS PERIOD 2 ElementAtomic# E- config dot struct Li 3 [He]2s 1 Li Be 4 [He]2s 2 B5 [He]2s 2 2p 1 C6 [He]2s 2 2p 2 N7 [He]2s 2 2p 3 O8 [He]2s 2 2p 4 F9 [He]2s 2 2p 5 Ne10 [He]2s 2 2p 6 B C N O F Ne Be

Lewis Dot Practice Time Complete the worksheet Read and underline the packet be prepared to discuss.

WRITING AND NAMING IONIC COMPOUNDS

A REMARKABLE FEATURE OF COMPOUNDS FORMED FROM ELEMENTS IS THAT THE PROPERTIES OF THE REACTANT ELEMENTS IS LOST +

WHEN AN ATOM LOSES OR GAINS ELECTRONS IN ORDER TO ACHIEVE ITS OCTET IT FORMS AN ION

THERE ARE ALSO COMBINATIONS OF ATOMS THAT HAVE AN IONIC CHARGE A.K.A. POLYATOMIC IONS POLY- MEANS MANY, BUT WE TREAT EACH OF THESE POLYATOMIC IONS AS A SINGLE UNIT WITH A SINGLE CHARGE

TODAY IS ALL ABOUT COMBINING THESE ELECTRICALLY CHARGED IONS TOGETHER TO FORM STABLE COMPOUNDS. REMINDER: WHEN TWO ATOMS COMBINE TRANSFERRING VALENCE ELECTRONS IT IS CALLED AN IONIC BOND.

AN IMPERFECT ATOM I WANT TO BE PERFECT!

IT COULD LOSE AN ELECTRON! WHAT DOES SODIUM NEED TO DO TO BECOME LIKE NEON?

IT COULD LOSE AN ELECTRON!

WHAT DOES SODIUM NEED TO DO TO BECOME LIKE NEON? NOW SODIUM IS MORE STABLE! 11 p’s -10 e’s +1 charge

I WANT TO BE PERFECT! AN IMPERFECT ATOM

IT COULD GAIN AN ELECTRON! WHAT DOES Cl NEED TO DO TO BECOME LIKE A NOBLE GAS, LIKE Ar?

- IT COULD GAIN AN ELECTRON! WHAT DOES Cl NEED TO DO TO BECOME LIKE A NOBLE GAS, LIKE Ar?

IT COULD GAIN AN ELECTRON! WHAT DOES Cl NEED TO DO TO BECOME LIKE A NOBLE GAS, LIKE Ar? 17 p’s -18 e’s -1 charge

28 Ionic Bonds Positive cations and the negative anions are attracted to one another (remember the Paula Abdul Principle of Chemistry: Opposites Attract!) Therefore, ionic compounds are usually between metals and nonmetals (opposite ends of the periodic table).

SO WHAT’S THE BOTTOM LINE? AN ATOM WILL SHARE, LOSE OR GAIN ENOUGH ELECTRONS TO BECOME MORE STABLE WITH 8 ELECTRONS IN ITS OUTERMOST ENERGY LEVEL. AND THEN IT WILL BOND WITH ANOTHER ATOM OF A DIFFERENT ELEMENT.

THINK ABOUT IT… FROM OUR PREVIOUS EXAMPLE SODIUM HAD AN EXTRA ELECTRON AND GAVE IT AWAY TO CHLORINE, WHICH WAS IN NEED OF ANOTHER ELECTRON. THIS FORMED A BRAND NEW COMPOUND, NaCl IN WHICH BOTH ELEMENTS WERE MORE STABLE

AN ELECTRON IS TRANSFERRED FROM THE Na ATOM TO THE Cl ATOM

BOTH ATOMS ARE HAPPY, THEY BOTH HAVE 8 ELECTRONS IN THEIR OUTERMOST ENERGY LEVEL. THIS IS AN IONIC COMPOUND

IONIC BOND bond formed between two ions by the transfer of electrons

Ionic Bonds: One Big Greedy Thief Dog!

OPPOSITELY CHARGED IONS ATT- RACT EACH OTHER AND FORM AN IONIC BOND THAT IS ELECTRICALLY NEUTRAL, LOOKING AT THE STRUCTURE OF SALT SHOWS THAT THE ATTRACTION BETWEEN IONS IS SO GREAT THAT MANY SODIUM AND CHLORIDE IONS BECOME INVOLVED

THE SMALLEST STACK OF THESE ANIONS AND CATIONS IS CALLED A UNIT CELL. UNIT CELLS ARE STACKED TOGE- THER TO MAKE UP A CRYSTAL LATTICE. CATIONS & ANIONS ARE PULLED TOGETHER IN A TIGHTLY PACKED STRUCTURE, WHICH GIVES IT A DISTINCTIVE STACKED SHAPE

PROPERTIES OF IONIC COMPOUNDS CAN CONDUCT ELECTRICITY WHEN MELTED IT FREES UP THE IONS TO MOVE PAST EACH OTHER PACK IN HIGHLY ORDERED ARRANGEMENTS IONS IN A SALT FORM REPEATING PATTERNS CALLED A CRYSTAL LATTICE

PROPERTIES OF IONIC COMPOUNDS HARD PACKED INTO LAYERS, TAKES A LOT OF ENERGY TO BREAK ALL OF THE BONDS BRITTLE IF A FORCE IS STRONG ENOUGH TO REPOS- ITION A LAYER THEN THE REPULSIVE FORCES DRIVE IONS APART

PROPERTIES OF IONIC COMPOUNDS HIGH MELTING POINTS AND BOILING POINTS BECAUSE OF STRONG ATTRA- CTION BETWEEN IONS, IT TAKES A LOT OF ENERGY TO BREAK THEM APART

THERE ARE A COUPLE OF RULES TO FOLLOW TO MAKE SURE THAT THE PROPER IONIC FORMULA IS WRITTEN. WRITING IONIC FORMULAS

RULE #1 IONS WILL COMBINE IN SMALL WHOLE NUMBER RATIOS THAT ADD TO GIVE A NEUTRAL COMPOUND. (Formula unit) THE IONS’ CHARGES MUST ADD UP TO ZERO

IT’S BETTER TO BE POSITIVE THAN NEGATIVE THE POSITIVE ION IS ALWAYS WRITTEN FIRST. RULE #2

SOME IONIC COMPNDS AUTOMATICALLY HAVE CHARGES THAT ADD UP TO ZERO.

WHAT IF WE WERE FORMING IONIC COMPOUNDS WITH IONS WHOSE CHARGES DIDN’T ADD UP TO A CHARGE OF EXACTLY 0? HOW DO WE DECIDE THE RATIO OF THE IONS?

WHAT IF WE HAD THREE CHLORINE IONS?

Finish Part 2 of worksheet Right now work! This is not the end of class

IT WILL TAKE 3 Cl -1 IONS TO EQUAL ONE Al +3 ION. WE HAVE A TRICK THAT WILL HELP US KNOW THE NUMBER OF THE IONS TO MAKE A NEUTRAL COMPOUND. IT’S NOT A TRICK SO MUCH AS A SHORTCUT!

CRISS-CROSS RULE:

MOST OF THE TIME YOU CAN NAME AN IONIC COMPOUND BY 1) WRITING THE NAME OF THE FIRST ELEMENT 2) WRITING THE ROOT OF THE NAME OF THE SECOND ELEMENT 3) ADDING -IDE TO THE ROOT NAMING THEM

NAMES OF NEGATIVE IONS PARENT ELEMENT NEGATIVE ION CHLORINECHLORIDE OXYGENOXIDE NITROGENNITRIDE PHOSPHORUSPHOSPHIDE FLUORINEFLUORIDE IODINEIODIDE SULFURSULFIDE BROMINEBROMIDE

NAMING THEM CaCl 2  K 3 P  Al 2 S 3  Calcium chloride Potassium phosphide Aluminum sulfide

SOME OF OUR METALS HAVE MORE THAN ONE IONIC CHARGE (oxidation number on PT) 1) WE HAVE TO FIGURE OUT WHICH CHARGE THE METAL HAS 2) THEN WE DESIGNATE THAT PARTICULAR METAL WITH A ROMAN NUMERAL NAMING THEM

FeCl 2  FeCl 3  PbBr 2  Iron(II) chloride Iron (III) chloride Lead (II) bromide NAMING THEM

IF THE COMPOUND HAS A POLYATOMIC ION IN IT 1) NAME THE FIRST ELEMENT 2) THEN NAME THE POLYATOMIC ION NAMING THEM

Fe(OH) 2  Ca 3 (PO 4 ) 2  Na 2 SO 4  Iron(II) hydroxide Calcium phosphate Sodium sulfate NAMING THEM