Unit 2: Molecular and ionic compound structure and properties

Question 1

Chemical Bonds

Answer 1

Attraction between the nucleus of one atom and the electron of another

*There’s a balance between attraction (+, -) and repulsion (+, +)(-, -)

Question 2

Bond Energy

Answer 2

Energy required to break the bond

Question 3

Bond Length

Answer 3

Distance between atoms

Question 4

Aspects of a single bond

Answer 4

• Fewest shared electrons
• Weaker attraction between nucleus of one atom and the bonding elements
• Weaker + Longer bond

Question 5

Aspects of a Triple Bond

Answer 5

• Most shared electrons
• Stronger attraction between nucleus of one atom and the bonding electrons
• Stronger + shorter bond

Question 6

Ionic Bonds

Answer 6

Electrostatic attraction between a cation (positively charged) and anion (negatively charged)

Question 7

Mg(OH)2 -> Mg^+2 + 2OH-, Lattice Energy: 2900

Sr(OH)2 -> Sr^+2 + 2OH-, Lattice Energy: 2300

Explain why in terms of periodic properties and Coulomb’s law that it takes less energy for Sr(OH)2 to separate its ions in terms of periodic property and Coulomb’s law.

Answer 7

Periodic property: The Sr^2+ ion is larger than the MG^2+ because it has more occupied energy shells; the bond length is longer and weaker

Coulomb’s Law: Since the distance between Sr^2+ and OH- is longer than the distance between Mg^2+ and OH-, the attractive forces in Sr(OH)2 are weaker, and its lattice energy is smaller

Question 8

Electronegativity

Answer 8

The ability of an atom in a molecule to attract shared electrons to itself

Question 9

Ionic bonds (electron definition)

Answer 9

Transferring electrons (usually involves a metal and nonmetal)

*think of it as: if the two elements differ in electronegativity, it is more ionic, and the more electronegative atom has more ability to attract or transfer shared electrons

Question 10

Covalent bonds

Answer 10

Sharing electrons (usually two nonmetals)

*think of it as: if two elements have similar electronegativity, covalent electrons share electrons more equally

Question 11

Nonpolar (covalent bond)

Answer 11

Electrons shared equally

Question 12

Polar (covalent bond)

Answer 12

Electrons shared unequally

Question 13

Metallic bonds

Answer 13

Electrons not associated with a atom or molecule (delocalized electrons)

Positive metal ions surrounded by a sea of mobile valence electrons

Question 14

Bond Polarity

Answer 14

Difference in electronegativity values of two elements

Question 15

δ− (negative partial charge)

Answer 15

Atoms with high electronegativity

Question 16

δ+ (positive partial charge)

Answer 16

Atoms with low electronegativity

Question 17

Dipole arrow points…

Answer 17

Towards the more electronegative atom

Question 17

A student claims that F2 is more polar than H2 because fluorine has a higher electronegativity than hydrogen. Do you agree with this claim?

Answer 17

No; Polarity is the difference in electronegativity, not the absolute value of the electronegativity. Fluorine and hydrogen have the same difference in electronegativity (0), so they have the same polarity.

Question 18

In order to conduct electricity, a substance must have…

Answer 18

• Charged particles
• particles that are free to move

Question 19

Alloys

Answer 19

Combining two or more metallic elements

Question 20

Substitutional allow

Answer 20

• Atoms of similar radii
• One atom substitutes for another atom in the lattice

Question 21

Interstitial alloy

Answer 21

• Atoms of different radii
• Smaller atom fills the spaces between larger atoms
• Usually the alloy is stronger than the base metal

Question 22

Octet rule

Answer 22

All atoms end up with 8 electrons around them

Question 23

Expanded Octet

Answer 23

Atoms in periods 3-7 can bond with other atoms in such a way they end up with more than 8 electrons in their octets

They can do this because they have d-orbitals in their outer shells that can accept electrons

Question 24

Formal charge

Answer 24

The hypothetical charge the atom would have if all of the atoms had the same electronegativity Calculated to identify the most stable/likely structure

Question 25

Formal charge formula

Answer 25

(# of valence electrons assigned to the neutral atom) - (# of electrons assigned to the atom in the structure) **bonds count as one!!!

Question 26

The potential energy of valence electrons ___ as they approach the nucleus of another atom

Answer 26

Decreases

Question 27

Bond energy is ___ during the formation of a bond

Answer 27

Released

Question 28

Potential energy and bond energy has an __ relationship

Answer 28

inverse

Question 29

As the # of bonds between 2 atoms increases, the bond length ___ and the bond energy ___

Answer 29

Decreases; Increases

Question 30

Bond Order

Answer 30

The number of bonds between two atoms

Question 31

Resonance Structures

Answer 31

A set of two or more Lewis Structures; occurs when a molecule has at least one double bond

Question 32

VSEPR Theory (Valence Shell Electron Pair Repulsion)

Answer 32

Charge clouds repel each other due to Coulombic repulsion- terminal atoms move as far away from each other as much as possible

Question 33

2 Charge clouds, 2 bonds, 0 lone pairs

Answer 33

Linear, 180 angle

Question 34

3 charge clouds, 3 bonds, 0 lone pairs

Answer 34

Trigonal Planar, 120 angle

Question 35

3 charge clouds, 2 bonds, 1 lone pairs

Answer 35

Bent, 120 angle

Question 36

4 charge clouds, 4 bonds, 0 lone pairs

Answer 36

Tetrahedral, 109.5 angle

Question 37

4 charge clouds, 3 bonds, 1 lone pairs

Answer 37

Trigonal Pyramidal, 107.3 angle

Question 38

4 charge clouds, 2 bonds, 2 lone pairs

Answer 38

Bent, 104.5 angle

Question 39

5 charge clouds, 5 bonds, 0 lone pairs

Answer 39

Trigonal Bipyramidal, 90 and 120 angle

Question 40

5 charge clouds, 4 bonds, 1 lone pairs

Answer 40

Seesaw, 90 and 120 angle

Question 41

5 charge clouds, 3 bonds, 2 lone pairs

Answer 41

T-Shaped, 90 angle

Question 42

5 charge clouds, 2 bonds, 3 lone pairs

Answer 42

Linear, 180 angle

Question 43

6 charge clouds, 6 bonds, 0 lone pairs

Answer 43

Octahedral, 90 angle

Question 44

6 charge clouds, 5 bonds, 1 lone pairs

Answer 44

Square pyramidal, 90 angle

Question 45

Rules of best Lewis diagram structure:

Answer 45

* Will have the minimum number of nonzero formal charges * If nonzero formal charges must remain, the negative charge must be assigned to the most electronegative atom * The sum of all the individual formal charges must add up to the charge of the chemical species

Question 46

6 charge clouds, 4 bonds, 2 lone pairs

Answer 46

Square Planar. 90 angle

Question 47

Molecular Geometry rules:

Answer 47

* Molecules composed of only nonpolar bonds are nonpolar, regardless of shape * Molecules in which the central atom is symmetrically surrounded by identical atoms are nonpolar, even if the bonds are polar * Molecules with asymmetrical shapes that contain any polar bonds are polar overall

Question 48

Symmetrical shapes:

Answer 48

Linear (3 atoms), trigonal planar, tetrahedral, trigonal bipyramidal, square planar, octahedral