Chemical Bonding and Nomenclature Chemical Bonding and Nomenclature

LET’S FIRST REVIEW IONIC BONDING Atoms can form molecules bonds: –IONIC –COVALENT –METALLIC Get to know the difference between IONIC and COVALENT BONDS based on what happens with the valence electrons.h

Opposites Attract! george-zaidan-and-charles-morton

In an IONIC bond, electrons are lost or gained, resulting in the formation of IONS in ionic compounds. FK

FK

FK

FK

FK + _

FK + _ The compound potassium fluoride consists of potassium (K + ) ions and fluoride (F - ) ions

FK + _ The ionic bond is the attraction between the positive K + ion and the negative F - ion

FK + _ But….how do we know what ions are formed by different elements? Octet Rule: Atoms want full valence shells to be stable

Forming Ions ElementValence e- Lose, gain, or share e- New Total electrons Charge of ion Li O P

Forming Ions ElementValence e- Lose, gain, or share e- New Total electrons Charge of ion Ga Kr Ba

How do we know how many atoms of each in an ionic bond? You did this yesterday Ionic Compounds are stable – NEUTRAL Negative charge must equal the positive charge

IONIC BONDS Look at the charge of each ion: Ca +2 & F -1 The charges do not balance – but they need to to get -2 charge to match Ca +2 charge we will need two F atoms

IONIC FORMULAS To write a proper formula, you need to say how many atoms of each HOW DO YOU WRITE one Ca atom and two F atoms? CaF 2 Subscripts: tells us number of atoms for each In example above, only 1 atom of Ca for the compound, so no subscript needed. F needs a subscript

Putting Ions Together-Formulas Na + + Cl - = NaCl Na + + O -2 = Na 2 O Al +3 + S -2 = Al 2 S 3 Ca +2 + N -3 = Ca 3 N 2 You try these! Mg +2 + F - = NH PO 4 -3 =K + + Cl - = Li + + Br - =MgF 2 (NH 4 ) 3 PO 4 KCl LiBr

Ion Formulas Remember those polyatomic ions (poly-many atomic-atoms) They stay whole in compounds, need more than one, must do so for whole ion: Ca +2 & PO 4 -3 cc: Written like this: Ca 3 (PO 4 ) 2

Ion Formulas There is an easy short cut to figuring out the formulas….using the charges to figure out the subscripts… CRISS CROSS METHOD Ca +2 & F -1 criss-cross:

Practice Use Criss Cross Strategy Use Criss Cross Strategy You will need periodic table You will need periodic table

IONIC Bonding Ionic Formula’s are RATIOS of Cations(+) to Anions(-) IONIC Bonding Ionic Formula’s are RATIOS of Cations(+) to Anions(-) Sodium and Oxygen combine Na +1 Oxygen -2 Na 2 O (two Na atoms for every O atom every time!)

Ionic Bonding Shortcut Criss Cross: use the charge of the positive charged element to determine the subscript for the opposite one Ionic Bonding Shortcut Criss Cross: use the charge of the positive charged element to determine the subscript for the opposite one Al +3 O -2 Al 2 O 3

Metal’s name goes first (cation)– do not change it except Iron = Ferrous Metal’s name goes first (cation)– do not change it except Iron = Ferrous Non-metal (anion) name is changed Non-metal (anion) name is changed End of original name taken off and replaced with “ide” oxygen = oxide nitrogen= nitride flourine= flouride End of original name taken off and replaced with “ide” oxygen = oxide nitrogen= nitride flourine= flouride REMEMBER Polyatomics stay as is, they keep their special names REMEMBER Polyatomics stay as is, they keep their special names Nomenclature Naming of Compounds FOR IONIC COMPOUNDS

Naming Examples Al 2 S 3 Al 2 S 3 Aluminum and Sulfur Aluminum Sulfide Aluminum Sulfide Fe 2 O 3 Ferrous (Iron) and Oxygen Ferrous Oxide Ferrous Oxide

Let’s Practice! Name the following. CaF 2 K 2 PO 4 SnF 2 SnF 4 CuI 2 CuI SrS LiOH Strontium Sulfide Lithium Hydroxide Copper ( I ) Iodide or Cuprous Iodide Copper ( II ) Iodide or Cupric Iodide Tin ( IV ) Flouride or Stannic Flouride Tin ( II ) Flouride or Stannous Flouride Potassium Phosphate Calcium Flouride

The Covalent Bond The Covalent Bond Atoms can form molecules by sharing electrons. Covalent Bonding – bonding by sharing electrons This is done only among non-metal atoms.

So what are covalent bonds?

In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule).

In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair Called a Bonding Pair.

Cl 2 Chlorine forms a covalent bond with itself

Cl How will two chlorine atoms react?

Cl What’s the solution – what can they do to achieve an octet? Each chlorine atom wants to gain one electron to achieve an octet

Cl

octet

Cl circle the electrons for each atom that completes their octets octet

Cl circle the electrons for each atom that completes their octets The octet is achieved by each atom sharing the electron pair in the middle

Cl circle the electrons for each atom that completes their octets The octet is achieved by each atom sharing the electron pair in the middle

Cl circle the electrons for each atom that completes their octets This is the bonding pair It is called a SINGLE BOND

Cl circle the electrons for each atom that completes their octets Single bonds are abbreviated with a dash Write this as an example of a single covalent bond

Cl circle the electrons for each atom that completes their octets This is the chlorine molecule, Cl 2

O2O2 Oxygen is also one of the diatomic molecules

How will two oxygen atoms bond? OO

OO Each atom has two unpaired electrons

OO

OO

OO

OO

O O Both electron pairs are shared.

6 valence electrons plus 2 shared electrons = full octet O O

6 valence electrons plus 2 shared electrons = full octet O O

two bonding pairs, O O making a double bond

O O = For convenience, the double bond can be shown as two dashes. O O

Let's Try it! H O H Water H 2 O 4 NB.O..O... H. H.

Let's Try it! H O H Water H 2 O 4 NB.. H..O..H..

Let's Try it! H O H Water H 2 O 4 NB.. H..O..H..

Let's Try it! H H N H Ammonia NH 3

Let's Try it! Ammonia NH 3 N H N

Let's Try it! Carbon Dioxide CO O::C::O.. O C O

Nomenclature Naming of Compounds FOR COVALENT COMPOUNDS Non-Metals and Non-Metals Use Prefixes such as mono, di, tri, tetra, penta, hexa, hepta, etc. EXCEPTION: don’t use prefix for first part of compound if it is just one atom of that ion or just one polyatomic ion CO 2 Carbon dioxide CO Carbon monoxide PCl 3 Phosphorus trichloride CCl 4 Carbon tetrachloride N 2 O 5 Dinitrogen pentoxide CS 2 Carbon disulfide

Let’s Practice! Name the following. OF 2 SO 2 Sulfur dioxide Oxygen diflouride N2S5N2S5 Din

Polyatomic Ions (partial list from page 195 (193 2 nd edition)) Ammonium……………... Ammonium……………... Nitrate…………………… Nitrate…………………… Permanganate………….. Permanganate………….. Chlorate………………… Chlorate………………… Hydroxide………………. Hydroxide………………. Cyanide…………………. Cyanide…………………. Sulfate…………………... Sulfate…………………... Carbonate………………. Carbonate………………. Chromate……………….. Chromate……………….. Acetate………………….. Acetate………………….. Phosphate………………. Phosphate………………. NH 4 + NH 4 + NO 3 - NO 3 - MnO 4 - MnO 4 - ClO 3 - ClO 3 - OH - OH - CN - CN - SO SO CO 3 2- CO 3 2- CrO 4 2- CrO 4 2- C 2 H 3 O 2 - C 2 H 3 O 2 - PO 4 3- PO 4 3-