Structure & Properties of Ionic & Covalent Compounds

Question 1

What is an ionic bond?

Answer 1

Attractive force due to transfer of 1 or more electrons from one atom to another

Question 2

What is a covalent bond?

Answer 2

Attractive force due to sharing of electrons between atoms

Question 3

Ionic Bonding

Answer 3

• Electron lost by a metal
• Electron gained by by a nonmetal
• two ions formed: cation and anion (of opposite charge =attracted)
• opposite charged ions held together by electrostatic force

Question 4

What is a crystal lattice?

Answer 4

Positive and negative ions arrange themselves in regular 3D repeating array to produce stable arrangement

Question 5

Covalent Bonding

Answer 5

• Each atom attains noble gas configuration by sharing electrons
• Tend to form between atoms with similar tendencies to gain or lose electrons
• Polar and nonpolar covalent bonding

Question 6

What are the diatomic elements?

Answer 6

Completely covalent bonds (totally equal sharing)
Example: Doctor BrINClHOF
Br2, I2, N2, Cl2, H2, O2, F2

Question 7

What is polar covalent bonding?

Answer 7

Bonds made up of unequally shared electron pairs

Reference notes for symbols

Question 8

What is electronegativity?

Answer 8

Measure of ability of atom to attract electrons in a chemical bond
- higher EN = greater ability to attract electrons than elements with low EN

Question 9

What is bond polarity?

Answer 9

Difference in electronegativity
Bond is:
-Ionic Bond: 🔺EN>1.9
- Polar Covalent Bond: .5🔺EN

Question 10

What does nomenclature mean? What are the two naming systems?

Answer 10

Assignment of correct & unambiguous name to each & every chemical compound

• ionic compound
• covalent compound

Question 11

How do you write the formula for an ionic compound?

Answer 11

1. Determine charge of each ion
   - metals: charge = group #
   - nonmetals: charge = group #-8
   - cations and anions combine to give formula with net change of 0
2. Name the cation followed by name of anion (change anion suffix to -ide)

Question 12

What is the stock system?

Answer 12

If a cation of the element has several ions of different charges (i.e. transition metals) use a Roman numeral following metal name
- Roman numerals give charge of metal

Question 13

What are common nomenclature system?

Answer 13

• use -ic to indicate higher of charges that ion might have

- use -ous to indicate lower of charges that ion might have

Question 14

What are monatomic ions?

Answer 14

Ions consisting of a single charged atom

Ex: all alkali metals, all halogen metals, be, ca, al, ag, ba, mg, o, s, n, p

Question 15

What are polyatomic ions?

Answer 15

Jons composed of 2 or more atoms bonded together with an overall positive or negative charge

Question 16

How to write formulas of an ionic compound from its name?

Answer 16

1. Determine charge of each ion

2. Write formula so resulting compound is neutral

Question 17

How do you name covalent bonds?

Answer 17

1. Write in order in which they appear in formula
2. Greek prefix indicates # of each kind of atom:
   - mono=1; di=2; tri=3; tetra=4; penta=5; hexa= 6; hepta=7; octa=8; nona=9; deca=10
3. If only one atom of a particular element is present in a molecule, prefix mono- is usually omitted in first element
4. Stem of name of last element is used with suffix -ide
5. Final vowel in prefix is often dropped before vowel in stem name

Question 18

What are the physical states of ionic and covalent compounds?

Answer 18

• ionic compound: usually solids at room temp

- covalent compound: usually solids, liquids, gases

Question 19

What is melting point?

Answer 19

Temperature at which solid is converted into a liquid

Question 20

What is boiling point?

Answer 20

Temperature at which a liquid is converted into a gas

Question 21

What are the melting points of ionic and covalent compounds?

Answer 21

• ionic compounds have higher melting points and boiling points
• covalent compounds have lower melting points and boiling points

Question 22

What are the structure of ionic and covalent compounds at solid state?

Answer 22

• ionic compounds are crystalline (organized)

- covalent compounds are crystalline (organized) or amorphous (unorganized)

Question 23

What is the difference between covalent and ionic compounds electrical conductivity?

Answer 23

Electrolytes: ions present in solution allowing solution to conduct electricity
Nonelectrolytes: covalent solids usually do not dissociate and do not conduct electricity

Question 24

How to draw a Lewis structure?

Answer 24

1. Use chemical symbols for various elements to write skeletal structure of compound
   - least electronegative atom will be placed in central position
2. Determine number of valence electrons associated with each atom in compound
   - combine valence electrons to determine total # of valence electrons in compound
3. Connect central atom to each of surrounding atoms with single bonds
4. Complete octets of all atoms bonded to central atom
   - lone pair: electrons not involved in bonding
5. If not enough valence electrons to give central atom an octet, move lone pair electrons from terminal atoms to form new bond with central atom
6. Recheck that all atoms have octet rule satisfied and total # of valence electrons used

Question 25

What are single bonds, double bonds, and triple bonds?

Answer 25

- single bond: one pair of electrons are shared between 2 atoms - double bond: 2 pairs of electrons are shared between 2 atoms - triple bond: 3 pairs of electrons are shared between z atoms

Question 26

What is bond energy?

Answer 26

Amount of energy required to break a bond holding 2 atoms together Triple bond> double bonds>single bond

Question 27

What is bond length?

Answer 27

Distance separating nucleI of 2 adjacent atoms | - single bond>double bond>triple bond

Question 28

What is resonance?

Answer 28

Two or more Lewis structures contribute to real structure

Question 29

What are the three exceptions to the octet rule?

Answer 29

1. Incomplete octet: less than 8 electrons around an atom other H 2. Odd electron: if there is an odd # of valence electrons, it is not possible to give every atom 8 electrons 3. Expanded octet: an element in 3rd period or below may have 10 and 12 electrons around it

Question 30

What is the VSEPR Theory?

Answer 30

Valence shell electron pair repulsion theory - used to predict shape of molecules - electrons arrange themselves as far away as possible to minimize electronic repulsion

Question 31

How does a linear structure look like?

Answer 31

-bonded atoms:2 -non binding lone electron pairs:0 -bond angle:180° -molecular geometry: linear Ex: CO2

Question 32

How does a trigonal planar structure look like?

Answer 32

``` Bonded Atoms: 3 Non bonding lone electron pairs: 0 Bond Angle: 120° Molecular Geometry: Trigonal planar Ex: SO3 ```

Question 33

How does a bent structure look like?

Answer 33

``` Bonded Atoms: 2 Non bonding lone electron pairs: 1 Bond Angle: < 120° Molécula Geometry: Bent Ex: SO2 ```

Question 34

How does a tetrahedral structure look like?

Answer 34

``` Bonded Atoms: 4 Non bonding lone electron pairs: 0 Bond Angle: 109.5° Molecular Geometry: tetrahedral Ex: CH4 ```

Question 35

How does a trigonal pyramidal structure look like?

Answer 35

``` Bonded Atoms: 3 Non bonding lone electron pairs: 1 Bond Angle: 107° Molecular Geometry: trigonal pyramidal Ex: NH3 ```

Question 36

How does a different bent structure look like?

Answer 36

``` Bonded Atoms: 2 Non bonding lone electron pairs: 2 Bond Angle: 104.5° Molecular Geometry: bent Ex: H2O ```

Question 37

How do you determine molecular shape?

Answer 37

1. Write Lewis structure 2. Count number of bonded atoms & lone pairs around central atom 3. If no lone pairs are present, geometry is: - 2 bonded atoms: linear - 3 bonded atoms: trigonal planar - 4 bonded atoms: tetrahedral 4. If there are lone pairs, look at the arrangement of atoms & name geometry

Question 38

How do you determine polarity?

Answer 38

1. Write Lewis structure 2. Draw geometry 3. Use following symbol to denote polarity of each bond Positive end of bond= less electronegative atom Negative end of bond= more electronegative atom attracts electrons more strongly towards it

Question 39

What are the guidelines for determining polarity?

Answer 39

- molecules that have no lone pair on central atom & all terminal atoms are same are non polar - molecules with one lone pair on central atom are polar - molecules with more than one pair on central atom usually polar

Question 40

What are intramolecular forces and intermolecular forces?

Answer 40

-Intramolecular Forces: attractive forces within molecules Ex: chemical bonds -Intermolecular Forces: attractive forces between molecules

Question 41

What is solubility?

Answer 41

Max amount of solute that dissolves in given amount of solvent at specific temperature Polar molecules: most soluble in polar solvents No polar molecules: most soluble in nonpolar solvents

Question 42

What is hydrogen bonding?

Answer 42

Attractive forces, called hydrogen bonds pull ammonia into water distributing ammonia molecules throughout water, forming homogeneous solution

Question 43

What factors influence boiling and melting points?

Answer 43

1. Strength of attractive force holding substance in its current physical state 2. Molecular mass - larger molecules have higher m.p. and b.p. than smaller molecules 3. Polarity - polar molecules have higher m.p. and b.p. than non polar molecules of similar molecular mass due to its strong attractive force