Chapter 07 and 08 Chemical Bonding and Molecular Structure

Compound Pure substance Made of 2 or more elements in a definite proportion by mass Physically and chemically different from the elements that make up the compound All elements (except Noble gases) react to gain a stable octet. (duet-for H through B) Compounds form to gain a stable valence shell which is LOWER IN ENERGY than the atoms before the reaction

Ionic compounds Metal gives all valence electrons to a nonmetal or semimetal. Both gain stable octets or duets. Ionic bond forms due to electrostatic attraction of cation(s) and anion(s) One unit is the lowest whole number ratio between the cation and anion. This unit is called a FORMULA UNIT

Covalent Compounds Formed when 2 or more nonmetals or a nonmetal and semimetal SHARE valence electrons in order to gain a stable octet. Tendency for atoms to obtain a stable octet is called the OCTET RULE.

Part 01 Ionic Bonding

1.Draw the electron dot (Lewis) Dot Diagram for the ionic compound formed between sodium and fluorine.

Na Atom F d Sodium must lose its one valence electron to get a stable octet. Fluorine must gain one electron to get a stable octet. The electron transfer is from sodium to fluorine and is always from metal to nonmetal.

[Na] Cation Anion This is an ionic compound because it contains a metal cation and a nonmetal anion. Both ions have a stable octet. The stable octet is NEVER shown on the cation; it is ALWAYS shown on the anion [ F ] d

This is a very stable compound. The positive and negative ions exerts a strong electrostatic attraction on each other and bond the ions together. [Na] Cation Anion 1+1- [ F ] d

The overall charge of the compound is zero because 1+ and 1- sums to zero. The overall charge must always be zero which shows that the number of electrons lost is equal to the number of electrons gained. [Na] Cation Anion 1+1- [ F ] d

Binary Ionic Salt Binary: Two Elements Ionic: Metal and Nonmetal Salt: Metal and Nonmetal Electron Dot or Lewis Dot Diagram [Na] Cation Anion 1+1- [ F ] d

Formula Shorthand method of representing a compound Electron Dot or Lewis Dot Diagram NaF 1+1- Metal on left Nonmetal on right Positive on left Negative on right ALWAYS [Na] Cation Anion 1+1- [ F ] d

Name Sodium Fluoride Electron Dot or Lewis Dot Diagram Names of all binary compounds end in –ide. [Na] Cation Anion 1+1- [ F ] d

2.Draw the electron dot (Lewis) Dot Diagram for the ionic compound formed between calcium and chlorine.

CaCl Atom Calcium must lose its TWO valence electrons to get a stable octet. Chlorine must gain one electron to get a stable octet. The electron transfer is from calcium to chlorine and is always from metal to nonmetal.

CaCl This is an ionic compound because it contains a metal cation and a nonmetal anion. Both ions have a stable octet. The stable octet is NEVER shown on the cation; it is ALWAYS shown on the anion.

This is a very stable compound. The positive and negative ions exerts a strong electrostatic attraction on each other and bond the ions together. 1- [Ca][ Cl ] CationAnion

The overall charge of the compound is zero because 2+ and 1- and 1- sums to zero. The overall charge must always be zero which shows that the number of electrons lost is equal to the number of electrons gained. 1- [Ca][ Cl ] CationAnion

Binary Ionic Salt Binary: Two Elements Ionic: Metal and Nonmetal Salt: Metal and Nonmetal Electron Dot or Lewis Dot Diagram 1- [Ca][ Cl ] CationAnion

Formula Shorthand method of representing a compound CaCl 2+1- Metal on left Nonmetal on right Positive on left Negative on right ALWAYS Electron Dot or Lewis Dot Diagram 2 1- [Ca][ Cl ] CationAnion

3.Draw the electron dot diagram for the ionic compound formed between potassium and oxygen.

K Atom O d Potassium must lose its one valence electron to get a stable octet. Oxygen must gain two electrons to get a stable octet. The electron transfer is from potassium to oxygen.

KO d This does not represent the formation of a compound. Oxygen does not have a stable octet because it has not gained two electrons.

A stable compound can form if a second potassium atom loses its one valence electron to the oxygen.

KO d K

[K] [ O ] d [K] The name of the compound is potassium oxide. Its formula is K 2 1+ O 2-. There are two electrons lost and two electrons gained.

4.Draw the electron dot diagram for the ionic compound formed between iron and bromine when iron has three valence electrons.

FeBr d Iron must lose its three valence electron to get a stable octet. Bromine can only gain one. The electron transfer is from iron to bromine.

Fe Br d d d The three electrons are transferred from the iron to the bromine when three bromine atoms are available.

[ Br ] [Fe] d [ Br ] d 1- [ Br ] d 1-

The name of the compound is iron(III) bromide. The Roman numeral is inserted after the name of the metal to indicate the number of electrons lost and the oxidation number. This is only done with elements that can change their oxidation numbers.

The formula of the compound is Fe 3+ Cl 1- 3.

Rule: Transition metals and lead and tin can have variable oxidation numbers. Therefore a Roman numeral must be inserted into the name of the compound to indicate the number of electrons lost and the oxidation number of the metal. Exceptions Ag is always 1+, Cd and Zn are 2+

What is the formula for: Calcium Fluoride Ca 2+ F 1- 2 Aluminum oxideAl 3+ O Tungsten(IV) SulfideW 4+ S 2- 2 Sodium CarbideNa 1+ C 4- 4 Go to page 73 in notes

What is the name of: Magnesium Carbide Scandium (III) Fluoride Silver Oxide NO ROMAN numeral! Tin (IV) Sulfide Francium Hydride Assignment: p (notes)