Exam 2

Question 1

Ionic bonding

Answer 1

electrostatic attraction between oppositely charged particles

Question 2

Lattice energy

Answer 2

energy change required to form a mole of crystalline lattice from a mole of each gaseous ion

Question 3

What happens as distance between ions increases?

Answer 3

Lattice energy decreases

Question 4

Covalent bonding

Answer 4

involves the sharing of electrons between 2 non metallic elements

Question 5

What type of bonding requires an empirical formula?

Answer 5

Covalent bonding

Question 6

Law of multiple proportions

Answer 6

same elements, but different ratio equals a completely different ratio

refers to covalent bonds

Question 7

Are covalent compounds molecules?

Answer 7

yes

Question 8

Are ionic compounds molecules?

Answer 8

no

Question 9

Lattice

Answer 9

positive and negative ions come together to form ionic compounds in a lattice structure

this structure consists of a positive cation surrounded by negative anions

Question 10

Properties of the ionic lattice

Answer 10

since there are so many attractive forces, it takes a large amount of energy to break them apart

this gives ionic lattices a high melting point

Question 11

Properties of covalent bonds

Answer 11

the covalent bonds inside the molecules are very strong

however, the forces attracting neighboring molecules are very weak

Question 12

Which has a lower melting point molecular bonds or ionic bonds?

Answer 12

Molecular bonds

because of weak force of attraction between molecules

Question 13

Is lattice energy positive or negative?

Answer 13

It depends on how you define it

If defined as splitting up a lattice into gaseous ions, then it will always be negative since it is an exothermic reaction (energy released)

If defined as a combining of gaseous ions into a lattice, then it will be positive since it is an endothermic reaction (energy required)

Question 14

Relationship between lattice energy and ionic bond strength

Answer 14

Greater lattice energy = greater ionic bond strength

It takes more energy to break apart ions since there is less distance between them and greater force of attraction

Question 15

What is lattice energy directly proportional to?

Answer 15

Charge

Question 16

What is lattice energy indirectly proportional to?

Answer 16

Distance between ions

Question 17

What happens to potential energy as two same charges get closer together?

Answer 17

Force of attraction decreases

So potential energy increases

Question 18

What happens to potential energy as two opposite charges get closer together?

Answer 18

Force of attraction increases

So potential energy decreases

Question 19

Potential energy “calibration” for opposite charges

Answer 19

Goes from more negative to less negative as distance between the electron and nucleus increases

as distance increases (force of attraction decreases), potential energy approaches 0 (increases)

Question 20

Is force of attraction greater in He+ or H (have the same protons)?

Answer 20

Greater in He+ because helium has more protons than hydrogen pulling at the one electron

Question 21

Why would Cr have the configuration [Ar] 4s1 3d5?

Answer 21

Having a two paired electrons in the 4s orbital makes electron-electron repulsion increase and thus potential energy goes up

Therefore, want to have no paired electrons because this decreases electron-electron repulsion and thus gives the overall system less energy

Question 22

Effective nuclear charge

Answer 22

the actual magnitude of the positive charge experienced by an electron

= (# of protons) - core electron shielding

Question 23

What is the relationship between effective nuclear charge and electron shielding?

Answer 23

As electron shielding increases, effective nuclear charge decreases

Question 24

Why are orbitals with the same energy level degenerate in hydrogen but not in multi-electron atoms?

Answer 24

Since hydrogen only has 1 electron, there are not other atoms to reduce the effective nuclear charge

For example, 2p is being affected by shielding from 2s so it bumps up to a higher energy level (feels less force of attraction, so has higher energy)

Question 25

Relationship between effective nuclear charge and atomic radius

Answer 25

As effective nuclear charge increases, atomic radius decreases since there is a stronger force of attraction

Question 26

What happens to atomic radius as you go down? Explain.

Answer 26

Increases Since the effective nuclear charge increases, but the core electrons also increase, there is less force of attraction, so the radius increases Also, n is increasing which indicates bigger size because there are more shells which increases shielding and distance

Question 27

Why does atomic radius decrease as you go across?

Answer 27

Since protons increase but core electrons (in the same shell) remain the same, there is a net effective nuclear charge increase which pulls electrons closer, thus decreasing the radius

Question 28

Ionization energy

Answer 28

the amount of energy needed to remove one mole of electrons from one mole of a certain element

Question 29

Why does it take energy to remove an electron from an atom?

Answer 29

Need to overcome the force of attraction Also think, you are moving to n = ∞, so need to absorb energy to increase n-level

Question 30

What happens as to ionization energy as you go down a column? Explain.

Answer 30

Ionization energy decreases Since n-level increases, the atomic radius increases and there is less force of attraction. Therefore, it takes less energy to remove an electron

Question 31

What happens to ionization energy as you go across a column? Explain.

Answer 31

Ionization energy increases Since effective nuclear charge increases (more protons), force of attraction is stronger and it takes more energy to remove an electron

Question 32

Why is it easier to remove electrons from the p-orbital than the s-orbital? (lower ionization energy)

Answer 32

s-orbital is more likely to be closer to the nucleus which results in stronger force of attraction than p-orbital

Question 33

Why does oxygen have lower ionization energy than nitrogen?

Answer 33

Oxygen has a paired electron orbital, whereas nitrogen has all unpaired electrons Since paired electron orbitals create electron-electron repulsion and lower effective nuclear charge, it is easier to remove an electron since less force of attraction

Question 34

Electron shielding

Answer 34

describes the decrease in force of attraction between the outermost electron and the nucleus due to paired electrons (greater electron-electron repulsion)

Question 35

Describe electron shielding in terms of energy

Answer 35

Since paired electron orbitals create electron-electron repulsion, there is an increase in energy an increase in energy indicates a decrease in force of attraction therefore, there is less of a force of attraction due to electron shielding

Question 36

Atomic number (Z)

Answer 36

number of protons the total positive charge in an atom

Question 37

Why is a cation smaller than its corresponding atom?

Answer 37

Since a cation looses an electron, each remaining electron experiences a greater effective nuclear charge from the protons therefore, force of attraction increases and cations are smaller

Question 38

Why is an anion larger than its corresponding atom?

Answer 38

Since an anion gains an electron, each electron experiences a lesser effective nuclear charge from the protons therefore, force of attraction decreases and anions are larger

Question 39

Why are electrons for transition metal cations removed from the s subshell instead of the d subshell?

Answer 39

3d is more likely to be closer to the nucleus based on radial probability, thus giving it a stronger force of attraction than 4s. Therefore, electrons are removed from 4s

Question 40

f-block and shielding

Answer 40

the f-block are poor shielders this creates a big increase in protons as we move down the periodic table that is unaccompanied by electrons not shielding which equals an overall higher effective nuclear charge

Question 41

Why is columbs law (force) directly proportional to lattice energy?

Answer 41

Because to break apart a strong force of attraction it requires a greater input of energy

Question 42

Why does the atomic radius not increase as you go across the transition metals?

Answer 42

As you add electrons to the d-block, you also increase shielding and therefore there is no net change in effective nuclear charge

Question 43

Nobel peace prize winners in chem 2018

Answer 43

George Smith, Frances Arnold, Greg Winter

Question 44

What to use when comparing force of attraction using Coulomb's law?

Answer 44

Magnitude

Question 45

What to use when comparing lattice energies?

Answer 45

Magnitude

Question 46

Relationship between ionic radius and lattice energy

Answer 46

Ionic radius is inversely proportional to lattice energy

Question 47

Why do ionic compounds want to form?

Answer 47

Energetically favorable In addition, being isoelectronic with noble gas configuration provides higher Zeff and correspondingly lower potential energy

Question 48

Why is energy released when a lattice forms?

Answer 48

Phase change from gas to solid (higher energy to lower energy) Also, force of attraction increases, so potential energy decreases

Question 49

What happens as the electron moves closer to another ion in order to form a lattice?

Answer 49

Force of attraction increases Potential energy decreases