Chapter 1: Atomic Structure

Question 1

What is the atomic number (Z)?

Answer 1

The atomic number Z of an element is equal to the number of protons found in an atom of that element.

Question 2

What is the mass number (A)?

Answer 2

The mass number A Is the sum of the protons and neutrons in the atoms nucleus.

Question 3

What is an isotope?

Answer 3

Isotopes of elements are atoms that share an atomic number, but have different mass numbers. Isotopes for an element have different masses due to having a different number of neutrons.

Question 4

What is the mass of an electron compared to that of a proton?

Answer 4

The mass of an electron is approximately 1/2000th that of a proton.

Question 5

What has more electrical potential energy, an electron farther away from the nucleus or electron closer to the nucleus?

Answer 5

Electrons farther away from the nucleus has higher electrical potential energy, electrons closer to the nucleus have lower electrical potential energy.

Question 6

What is a positively charged atom called?

Answer 6

A positively charged atom is called a cation.

Question 7

What is a negatively charged atom called?

Answer 7

A negatively charged atom is called an anion.

Question 8

Table showing some basic features of the three subatomic particles.

Answer 8

Question 9

Determine the number of protons, neutrons, and electrons in a nickel – 58 atom and a nickel – 60+2 cation.

The atomic number for Ni is 28 and a mass number of 58.

Answer 9

58 – Nickel has an atomic number of 28 and a mass number of 58. Therefore, 58 – nickel will have 28 protons, 28 electrons, and 30 neutrons (58 - 28).

60 – nickel 2+ has the same number of protons as the neutral 58 – nickel atom. However, 60 – nickel 2+ has a positive charge because it has lost two electrons. Nickel 2+ will have 26 electrons. Also, the mass number is two units higher than for 58 nickel atom, and the difference in mass must be due to two extra neutrons; thus, it has a total of 32 neutrons.

Question 10

What subatomic particle is the most important for determining charge?

Answer 10

The electron is a subatomic particle most important for determining charge.

Question 11

What subatomic particle is the most important for determining atomic number?

Answer 11

The proton is the subatomic particle most important for determining atomic number.

Question 12

What subatomic particle is the most important for determining isotopes?

Answer 12

Neutrons are the subatomic particle most important for determining isotopes. Protons make up part of the mass number, it is the number of neutrons that explains the variability between isotopes.

Question 13

Determine the number of protons, neutrons and electrons in 18 – oxygen and 18 – fluorine.

The atomic number for oxygen is eight, the atomic weight for oxygen is 16.

The atomic number for fluorine is nine, the atomic weight of fluorine is 19.

Answer 13

For the isotope 18 – oxygen, there will be eight protons, eight electrons, and 10 neutrons.

For the isotope 18 fluorine, there will be nine protons, nine electrons, and nine neutrons.

Question 14

What is the atomic number Z, the mass number A, how do you calculate the number of electrons in a neutral atom, and are electrons included in mass calculations, what is significant about the number of protons?

Answer 14

The atomic number Z equals the number of protons.

The mass number A equals the number of protons plus the number of neutrons.

The number of electrons in a neutral atom is equal to the number of protons.

Electrons are not included in mass calculations.

The number of protons determine the kind of atom it is. The number of neutrons determine the isotope.

Question 15

How is an atomic mass unit defined?

Answer 15

Atomic mass unit is defined as exactly 1/12 the mass of carbon – 12 atom.

Question 16

Is the mass of a proton the mass of a neutron the same?

Answer 16

No. Neutrons are slightly more massive than protons. In fact, the mass difference is approximately equal to the mass of an electron.

Question 17

What are the three isotopes that are given unique names?

Answer 17

The three isotopes of hydrogen are the only three isotopes given unique names:

Protium: has one proton and an atomic mass of one AMU.

Deuterium: has one proton and one neutron and an atomic mass of two AMU.

Tritium: has one proton and two neutrons and an atomic mass of three AMU.

Question 18

What is the atomic mass (mass number) of an atom?

Answer 18

The atomic mass of an atom is nearly equal to its mass number, the sum of protons and neutrons.

Question 19

What is atomic weight and how does it differ from atomic mass?

Answer 19

Atomic weight is the reported on the periodic table and is the weighted average of different naturally occurring isotopes. Atomic mass is the mass of a particular element.

Question 20

What is Avogadro’s number and why is it significant for chemistry?

Answer 20

Avogadro‘s number is 6.02x10-23 “things”. Avogadro’s number is significant in chemistry because the atomic weight is the mass of one mole of that element in grams. One mole is equal to Avogadro‘s number.

Example. The atomic weight of carbon is 12.0 AMU, which means that the average carbon atom has a mass of 12.0 AMU. 6.02x10-23 carbon atoms weighs 12 grams,
(12 grams/mole)

Super important to recall this.

Question 21

Element Q consist of three different isotopes: A, B, and C.

A has an atomic mass of 40 AMU accounts for 60% of the naturally occurring Q.

B has an atomic mass of 44 AMU accounts for 25% of naturally occurring Q.

C has an atomic mass of 41 AMU account for 15% of naturally occur occurring Q.

What is the atomic weight of element Q?

Answer 21

You calculate the atomic weight of Q by multiplying the proportion of the naturally occurring isotopes with her AMU in finding the sum total of those numbers.

0.60(40 AMU)+0.25(44 AMU)+0.15(41 AMU)=
24 AMU+11 AMU+6.15 AMU= 41.15 AMU

Question 22

What’s the definition of atomic mass, atomic weight?

Answer 22

The definition of atomic mass is this sum total of protons and neutrons in a given atom of an element.

The definition of atomic weight is the average mass in AMU of the naturally occurring isotope of a given element.

Question 23

Molar mass is typically written in grams per mole, is the ratio moles per gram also acceptable?

Answer 23

The ratio is an equivalent concept. It is therefore acceptable as long as units can be canceled in dimensional analysis.

Question 24

What is equation of Planck’s relation (energy of a quantum)?

Answer 24

E=hf

Where E is energy.
h is Planck’s constant (6.626x10- (-34)) Jxs
f is the frequency of the radiation

Question 25

What is Planck’s constant?

Answer 25

Planck’s constant is a proportionality constant that relates energy of a quantum and frequency of the radiation.

6.626x10- (-34) J x s

Where J are joules and s is seconds.

Question 26

What is the speed of light?

Answer 26

Speed of light is 3x10-8 m/s

Question 27

What is the equation for classical kinetic energy?

Answer 27

K=1/2 mv-2

Units are joules (kg metersq/secondsq)

Question 28

What is the classical equation for angular momentum?

Answer 28

L=mvr

Where m is mass
v is velocity
r is radius

Question 29

What is Bohr’s Prediction of the possible value for the angular momentum of an electron orbiting a hydrogen nucleus?

Answer 29

L = nh/2pi

n is the principle quantum number (which can be any positive integer). Notice higher n means higher angular momentum.

h is Planck’s constant. Super interesting. Super interesting: h/2pi is known as h-bar and is specifically used in physics to calculate quantum angular momentum.

Notice that the only variable is the principal quantum number, the angular momentum of an electron changes only in discrete amounts with respect to the principal quantum number.

Question 30

What is Bohr’s Equation for the energy of an electron around an atom?

Answer 30

E = — Rh/nsquared

Rh Is the experimentally determined Rydberg unit of energy (2.18x10- —18 J/e)

n is the principle quantum number.

Again, the energy of the electron changes in discrete amounts with respect to the quantum number.

The value of zero energy was assigned to the state in which the proton and electron are separated completely, meaning that there is no attractive force between them. Electron in any of its states in the atom will have an attractive force toward the proton; this is represented by the negative sign in the equation.

The only thing the energy equation is saying is that the energy of an electron increases, becomes less negative, the farther out from the nucleus that it is located (increasing n).

While the magnitude of the fraction is getting smaller, the actual value it represents is getting larger (becoming less negative).

Question 31

Talk about how much you understand the energy of the electron equation.

Answer 31

Energy (E) is indirectly proportional to the principal quantum number n. The negative sign causes the values to approach from a more negative value as n increases, increasing the energy. This equation follows the inverse square law but in discrete positive integers of n.

The value of zero energy was assigned to the state in which the proton and electron are separated completely meaning that there is no attractive force between them.

The electron in any of its excited states in the atom will have an attractive force towards the proton represented by the negative sign.

The energy of an electron increases, becomes less negative, the farther out from the nucleus that it is located (increasing n). The magnitude of the fraction is getting smaller, the actual value represents is getting larger (becoming less negative).

Question 32

What is the defined pathway of an electron called?

Answer 32

The defined pathway of an electron is called an orbit and has a discrete energy value.

Question 33

Define the ground state of an atom.

Answer 33

The ground state of an atom is the state of lowest energy in which all electrons are in the lowest possible orbitals.

Question 34

Define excited state of an atom.

Answer 34

Excited of an atom is at least one electron has moved to a subshell of higher than normal energy, excited by light or heat or chemical energy. Excited atoms become excited in specific increments or quanta, meaning it takes a highly specific amount of energy to excite atoms of given nature. Can relate this to line spectrums and atomic emission spectrums.

Question 35

As electrons go from a lower energy to a higher energy level, they get AHED. Describe.

Answer 35

Absorb light
Higher potential
Excited
Distant from nucleus

Question 36

Briefly describe the theory of atomic emission spectra.

Answer 36

Electrons can be excited to higher energy levels by heat or other energy forms to yield excited states. Because the lifetime of an excited state is brief, the electrons will return rapidly to the ground state, resulting in the emission of discrete amounts of energy in the form of photons.

Electrons in an atom can be excited to different energy levels. When these electrons return to their ground states, each will emit a photon with a wavelength characteristic of the specific energy transition undergoes. These energy values are not a continuum, but rather quantized to certain values.

Question 37

What is the equation for the electromagnetic energy of photons? What two equations is this combined to form?

Answer 37

The equation for the electronic energy of photons is:

E=hc/lambda

h is Planck’s constant (6.626x10- —34 Js)
c is speed of light (3x10-8 m/s)
lambda is the wavelength of the radiation

Notice that there is no n quantum number because the question isn’t asking about photons related to emission or absorption.

Note that the longer the wavelength the lower the energy of the photon.

This is a combination of:

E=hf and c=f(lambda) (f=c/lambda)

Question 38

What is a line spectrum?

Answer 38

A line spectrum is composed of light at specific frequencies where each line on the emission spectrum corresponds to a specific electron transition.

Question 39

What is atomic emission spectrum?

Answer 39

Atomic emission spectrum is a unique energy signature of an element or compound.

Because each element can have its electrons excited to a different set of distinct energy levels, each possesses a unique atomic emissions spectrum, which can be used as a fingerprint for the element.

Atomic emissions spectroscopy can be used in the analysis of stars and planets. The light from a star can be resolved into its component wavelengths, which then are matched to the known line spectrum of the elements.

Question 40

The Bohr model of the hydrogen atom explain the atomic emission spectrum of hydrogen, which is the simplest emission spectrum among all the elements. There are three series associated with the hydrogen emission lines corresponding to transitions from energy levels. What are those series call and what what do they represent?

Answer 40

The three series of hydrogen emission spectrum are:

Lyman series: n=1 transitioning from n>2

Balmer series: n=2 transitioning from n>3

Paschen series: n=3 transitioning from n>4

Note: all of these series transitions are greater than or equal to.

Question 41

What is the equation to convert wavelength and frequency of light?

Answer 41

c=f(lambda)

C is speed of light (3x10-8 m/s, 3x10-17 nm/s)

f is frequency

lambda is wavelength

Question 42

How do you calculate the energy associated with the change in the principal quantum number for the higher initial value to a lower final value?

Answer 42

By combining Bohr’s and Planck’s calculations, we can derive this equation:

E=hc/lambda = Rh [1/ni-2 — 1/nf-2]

Where ni is initial quantum state and nf is final quantum state.

Rh is Rydberg unit of energy:
(2.18x10-18 J/electron)

Question 43

Talk about the following equation:

Answer 43

This equation says that the energy of the emitted photon corresponds to the difference in energy between the higher energy initial state and the lower energy final state.

Note that this is initial minus final. If an atom emits a photon, the equation gives him negative value for energy, indicating a decrease.

Question 44

What is absorption spectrum and why is it important?

Answer 44

In addition to a unique emission spectrum, every element possesses a characteristic absorption spectrum. Absorption is the basis for the color of compounds, we see the color of the light that is not absorbed by the compound.

The Takeaway regarding atomic emission and absorption spectra is that each element has a characteristic set of energy levels. For electrons to move from a lower energy level to a higher energy level, they must absorb the right amount of energy to do so.

Question 45

What is the Heisenberg uncertainty principle, and how does it differ from the Bohr model?

Answer 45

The Heisenberg uncertainty principal states it is impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron. If we want to assess the position of electron, the electron has to stop (thereby removing its momentum), if we want to assess its momentum, the electron has to be moving (thereby changing position).

The Bohr model postulated that electrons follow a clearly defined circular pathway at a fixed distance from the nucleus, whereas modern quantum mechanics has shown that this is not the case. We now understand that electrons move rapidly and are localized in regions of space around the nucleus called orbitals.

Question 46

What is the Pauli exclusion principle?

Answer 46

The Pauli exclusion principal states that no two electrons in a given atom can possess the same set of four quantum numbers. For a given value of n, only particular values of l are permissible, for value of l, only particular values of ml are permissible, and electrons will always have different ms (spin quantum number) in an orbital.

Question 47

What is the principal quantum number (n)?

Answer 47

The principal quantum number (n) is the quantum number used in Bohr’s model that can theoretically take on any positive integer value. The larger the integer value of n, the higher the energy level and radius of the electron’s shell.

Question 48

What is the equation for the maximum number of electrons within a shell?

Answer 48

2n-2

(2nsquared)

Example:

First energy level (H and He) 2(1)squared=2
2nd: 2(2)squared= 8
3rd: 2(3)squared= 18 (s,d, and p orbitals)

Question 49

What is the difference in energy of an electron a function of?

Answer 49

The difference in energy of an electron is a function of:

[(1/ni-2)-1/nf-2)]

For example, the difference in energy level from n=3 and n=4 ((1/9)-(1/16)) is less than the energy difference me between n=1 and n=2 ((1/1)-(1/4)).

Question 50

What is the quantum number l?

Answer 50

l is the azimuthal (angular momentum) quantum number. The second quantum number refers to the shape and number of subshells within a given principal energy level (shell).

Specifies which orbital the electron is located:
l=0, s (one ml orbital: 0)
l=1, p (3 ml orbitals: -1,0,+1)
l=2, d (5 ml orbitals: -2,-1,0,+1,+2)
l=3, f (7ml orbitals: -3,-2,-1,0,+1,+2,+3)

Question 51

How does the principal quantum number (n) limit the azimuthal (angular momentum) quantum number (l)?

Answer 51

The principal quantum number (n) limits the azimuthal (angular momentum) quantum number in the following way:

For any given value of n, the range of possible values for l is 0 to (n-1).

Example.
For n=1, the only possible value for l is 0.
For n=2, the only possible values for l are 0 and 1.

Therefore:
there’s only one subshell (l=0) in the first principal energy level (n=1)
There are two subshells (l= 1,0) in the second principle energy level (n=2)
There are three subshells (l=0,1,2) in the third principle energy level (n=3)
And so on.

Question 52

What is spectroscopic notation?

Answer 52

Spectroscopic notation refers to the shorthand representation of the principal and azimuthal quantum numbers. The principal quantum number remains a number, but the azimuthal quantum number is designated a letter:

l=0 is s
l=1 is p
l=2 is d
l=3 is f

Example.

An electron in the shell n=4 and subshell l=2 would be in the 4d subshell.

An electron in the shell n=2 and subshell l=1 would be in the 2p subshell.

An electron in the shell n=1 and subshell l=0 would be in the 1s subshell.

Question 53

What is the equation for the capacity to hold a certain number of electrons WITHIN A SUBSHELL (s, p, d, f)?

Answer 53

With each subshell, there is a capacity to hold a certain number of electrons, given by the equation:

4l+2

Where l is the azimuthal quantum number.

s subshell (l=0) 4(0)+2= 2 electrons
p subshell (l=1) 4(1)+2= 6 electrons
d subshell (l=2) 4(2)+2= 10 electrons
f subshell (l=3) 4(3)+2= 14 electrons

The energies of the subshell increase with increasing l value; however, the energies of subshells from different principal energy levels may overlap.

For example, the four subshell will have a lower energy than the 3d subshell.

Question 54

Computer imaging for rough visual representation of the shapes of different subshells.

Answer 54

Question 55

What is the magnetic quantum number (ml)?

Answer 55

Magnetic quantum number specifies the particular orbital within a subshell or an electron is most likely to be found at a given moment in time. Each orbital can hold a maximum of two electrons.

Question 56

What are the possible values of the magnetic quantum number (ml)?

Answer 56

The possible values of the magnetic quantum number (ml) are integers between -l and +l, including 0.

2l+1

For example:

The s subshell, with l=0, limits the possible magnetic quantum number (ml) values to 0, and because there is a single value of ml, there is only one orbital in the s subshell.

The p subshell, with l=1, limits the possible ml values to ml= -1,0, and +1, and because there are three values for ml there are three orbitals in the p subshell.

The d subshell has five orbitals (-2,-1,0,+1,+2)

The f subshell has seven orbitals (-3 to +3)

Question 57

How do you find the magnetic quantum number (ml) using the azimuthal quantum number (l), how many orbitals for any n, how many electrons for any value n?

Answer 57

For any value of l, there will be 2l+1 possible values for ml.

For any n, this produces nsquared orbitals.

For any value of n, there will be a maximum of 2nsquared electrons (2 per orbital).

Question 58

What is the spin quantum number (ms)?

Answer 58

The spin quantum number a quantum feature of electrons loosely related to spin. Electrons only have two spin orientations designated as +1/2 or -1/2. Whenever two electrons are in the same orbital, they must have opposite spins.

Question 59

What is the name for two electrons in the same orbital (must be spinning opposite), and the name for electrons and different orbitals with the same ms value?

Answer 59

Two electrons in the same orbital are referred to as being paired. Electrons in different orbitals with the same ms values are said to have parallel spins.

Question 60

What are electron configurations?

Answer 60

For given atom or ion, the pattern by which subshells are filled as well as the number of electrons within each principle energy level and subshell are designated by its electron configuration.

Electron configurations use spectroscopic notation, wherein the first number denotes the principal energy level, the letter designates the subshell, and the superscript gives the number of electrons in that shell.

For example:

2p4 indicates that there are four electrons in the second (p) subshell of the second principle energy level. This implies that the energy levels below 2p (1s and 2s) have already been filled.

Question 61

What is Aufbau principal?

Answer 61

The Aufbau principle (the build up principle) states that electrons fill from lower to higher energy subshells and each subshell will fill completely before electrons begin to enter the next one.

Audbau is German for “to build”

Question 62

What is the rule for helping figure out the lower of two energy subshells?

Answer 62

The n+l rule is a helpful way to figure out the lower energy of any two subshells. The lower the sum of the values, the lower the energy of the subshell and thus will be the first to be filled with electrons. If the two subshells have the same n+l value, the subshell with the lower n value has the lower energy and will fill with electrons first.

Question 63

Use the n+l rule to figure out which subshell will fill first: 5d or 6s.

Answer 63

5d has an n value of 5 and an l value of 2, so n+l=5+2=7.

6s has an n value of 6 and an l value of 0, so n+l=6+0=6.

6<7 therefor the 6s subshell is lower energy and thus will fill with electrons first.

Question 64

Use the n+l rule to find out which is the lower energy subshell and thus will fill first with electrons:

3d or 4p

Answer 64

3d: n=3, l=2, n+l=5
4p: n=4, l=1, n+l=5

Same n+l, so lower n fills first.

3d will fill before 4p.

Question 65

You can figure out electron configurations through simply reading the periodic table. You will need to know where the lanthanide and actinide series series go (f orbitals) as well as how to read how electrons fill their orbitals. So, where and how?

Answer 65

The lanthinide and actinide series go between the s and d sections starting at row 6. Read left to right across entire rows, moving down a row when finished at the end (noble gases).

Question 66

Electron configurations can be abbreviated by placing the noble gas that proceeds the element of interest in brackets. What would be the electron configuration of osmium (Z=76)?

Answer 66

Xenon is the noble gas in the row above osmium. So:

[Xe] 6s2 4f14 5d6

Question 67

What would be the electron configuration of chromium (Z=24) and copper (Z=29)

Answer 67

This is a trick question. These two are the two example to be remembered that are unique amongst the classic way of electrons filling orbitals.

Using classic Hund’s rule, chromium would be [Ar] 4s2 3d4 and copper would be [Ar] 4s2 3d9.

However, these two are different and are actually chromium: [Ar] 4s1 3d5 and copper: [Ar] 4s1 3d10.

Question 68

Explain how to find electron configurations for cations and anions.

Answer 68

Anions (negatively charged ions) have additional electrons and are filled according to the same rules as generally filling electron orbitals. For example, if fluorine’s electron configuration is [He] 2s2 2p5, then F- will be [He] 2s2 2p6.

Cations (positively charged ions) are a bit more complicated: start with the neutral atom, and remove electrons with the highest value for n first. If multiple subshells are tied for highest n value, then electrons are removed from the subshell with the highest l value among them.

Example of cation electron configuration:

Fe 3+. Neutral state Fe is [Ar] 4s2 5d6. At first you would think that it would be [Ar] 4s2 3d3. However, it is [Ar] 5d5. We need to remove the electrons from the highest n value first, in this case 4s. Take two from 4s first, then another from 3d (for a total of three because it’s asking about Fe 3+).

Question 69

What is Hund’s rule?

Answer 69

Hund’s rule states that within a given subshell, orbitals are filled such that there are a maximum number of half filled orbitals with parallel spins. The basis for this preference is electron repulsion: electrons in the same orbital tend to be closer to each other, and thus repel each other more than electrons placed in different orbitals.

It’s like finding a seat on a crowded bus. Electrons would prefer to have their own seat (orbital) before being forced to double up with another electron.

Question 70

According to Hund’s rule, what are the orbital diagrams for nitrogen and iron?

Answer 70

Question 71

What are two notable exceptions to electron configuration, and therefor Hund’s rule?

Answer 71

The two notable exceptions to electron configuration are chromium (Z=24) and copper (Z=29) and other elements in their group.

Chromium, strictly following Hund’s rule would be [Ar] 4s2 3d4 but is actually 4s1 3d5.
Copper, strictly following Hund’s rule would be [Ar] 4s2 3d9, but is actually 4s1 3d10.

Similar shifts can happen in the same group with d and f subshells, but never happen with p subshells.

This is due to the energetic favorably of filling the d subshell outweighs the energetic favorably of filling the s subshell. This is just something that has to be recognized and memorized.

Question 72

What is paramagnetic?

Answer 72

Paramagnetic materials composed of atoms with unpaired electrons will orient their spins and alignment with a magnetic field, and the material will be weakly attracted to a magnetic field. These materials are known as paramagnetic.

Remember that paramagnetic means that magnetic field will cause parallel spins in electrons and therefore cause an attraction.

Question 73

What is diamagnetic?

Answer 73

Materials consisting of atoms that have only paired electrons will be slightly repelled by a magnetic field. These materials are said to be diamagnetic.

Question 74

What is an allotrope?

Answer 74

An allotrope is a form of a chemical element that can exist in the same physical state as other forms of the element, but with different chemical and physical properties.

For example. Carbon allotropes are diamonds, graphite, buckyballs. Same atom, different physical and chemical properties.

Question 75

What are valence electrons?

Answer 75

Valence electrons of an atom are those electrons that are in its outermost energy shell, are most easily removed, and are available for bonding. In other words, the valance electrons are “active“ electrons of an atom into a large extent, dominate the chemical behavior of an atom.

Question 76

What shell are the valence electrons for groups IA and IIA (groups 1 and 2), groups IIIA and VIIIA (groups 13-18), for transition elements, and for lanthanide and actinide series, and all elements in period 3 and below (starting with sodium)?

Answer 76

Valence for 1 and 2 are only the highest s subshell electrons.

Valence for 13-18 are the highest s and p subshell electrons.

Valence for transition elements are electrons in the highest s and d subshells.

Valence for lanthanide and actinide series are electrons in highest s and f subshells (even though they have different principle quantum numbers)

All elements in period 3 (starting with sodium) and below may accept electrons into their d subshell which allow them to hold more than 8 electrons in their valence shell, violating the octet rule. Just gotta remember this last point.

Question 77

Which electrons are the valence electrons of elemental vanadium, elemental selenium, and the sulfur atom and sulfate ion?

Answer 77

Vanadium has five valence electrons: two in its 4s subshell and three in its 3d subshell.

Selenium has six valence electrons: two in its 4s subshell and four in its 4p subshell. Selenium’s 3d electrons are not part of its valence shell.

Sulfur in a sulfate ion has 12 valence electrons: its original 6+6 more from the oxygens to which it is bonded. Sulfurs 3s and 3p subshells can only contain eight of these 12 electrons; the other four electrons have entered the sulfur atom’s 3d subshell, which is normally empty and elemental sulfur.

Question 78

What is the octet rule?

Answer 78

The octet rule refers to the tendency of atoms to prefer to have eight electrons in the valence shell. When atoms have fewer than eight electrons, they tend to react and form more stable compounds. When discussing the octet rule, we do not consider d or f electrons.

Question 79

The atomic weight of hydrogen is 1.008 AMU. What is the percent composition of hydrogen by isotope, assuming that the only hydrogen isotopes are 1H and 2D.

Answer 79

This question need a series of equations set up to solve for 2 variables (H and D).

The first equation to recognize is:

H+D=1

Then, using the information given in the question:

1H+2D=1.008 AMU

Solve for D (or H) by manipulating one equation and entering it into the other to solve for one of the variables.

Question 80

Calculation to be comfortable with:

P21 Q1

Answer 80

Question 81

Calculation to be comfortable with:

P21 Q2

Answer 81

Question 82

Calculation I should be comfortable with:

P21 Q3

Answer 82