Atomic Structure & Periodic Table

Question 0

Neutral atoms have…

Answer 0

The number of electrons outside the nucleus is equal to the number of protons inside the nucleus. Electrons are held in the atom by the electrical attraction of the positively charged nucleus

Question 1

What is an Atom?

Answer 1

The smallest unit of any element. All atoms have a central nucleus which contains protons and neutrons known as nucleons. Each proton has an electric charge of +1; neutrons have no charge. Outside the nucleus are electrons each have an electric charge of -1

Question 2

What is the atomic number of an atom?

Answer 2

Symbol= Z
Number of protons
Shown in a subscript before the element

Question 3

Mass of proton and neutron

An electron?

Answer 3

Each have a mass slightly more than one atomic mass unit (1 amu =1.66x10^-27 kg)
An electron has a mass that’s only 0.05% the mass of either a proton or a neutron
All the mass of an atom is due to the nucleus

Question 4

Atomic mass equals

Answer 4

A=Z+N

Atomic mass is written as a super sub script before the elements

Question 5

Isotopes

Answer 5

If two atoms of the same element differ in their numbers of neutrons they are called isotopes.
This affects only the mass number.

Question 6

And item would seven neutrons and a mass number of 12 is an isotope of what element?
A. Boron
B. Nitrogen
C. Magnesium
D. Potassium

Answer 6

A. Boron
A equals 12
N equals 7
So Z would equal 5 which is the atomic number
Remember the atomic number is not affected in an isotope

Question 7

Are elements found in their one form in nature?

Answer 7

Elements exist naturally as a collection of the isotopes. The atomic weight of an element is a weighted average of the masses of its naturally occurring isotopes.
In order to get the weighted average the isotopes are multiplied by the percentages which they occur in the natural world and then added
Atomic weight of an element or the weighted average is found on the periodic table

Question 8

What are ions?

Answer 8

What a neutral atom gains or loses electrons, it becomes charged, and the resulting atom is called an ion.
For each electron it gains, and atom acquires a charge of -1 unit, and for each electron it loses an atom acquires a charge of a +1 unit. A negatively charged ion is called an anion, while a positively charged ion is called a cation.

Question 9

What is the strong nuclear force?

Answer 9

Protons and neutrons in the nucleus are held together by force called the strong nuclear force. It is stronger than the electrical force between charged particles, since for all atoms besides hydrogen, the strong nuclear force must overcome the electrical repulsion between the protons.
In fact, of the four fundamental forces of nature, the strong nuclear force is the most powerful even though it only works over extremely short distances.

Question 10

Unstable nuclei are?

Answer 10

Said to be radioactive, and they undergo a transformation to make them more stable altering the number and ratio of protons and neutrons or just lowering their energy.
Such a process is called radioactive decay, and there are three types alpha, beta, and gamma.
The nucleus that undergoes radioactive decay is known as the parent.
And the resulting more stable nucleus is known as the daughter.

Question 11

What are the three types of radioactive decay?

Answer 11

Alpha, beta, gamma

Question 12

What is alpha decay?

Answer 12

When a large nucleus wants to become more stable by reducing the number of protons and neutrons, it emits an alpha particle.
An alpha particle, denoted by 4/2 (alpha sign), consist of two protons and two neutrons.
Alpha decay reduces the parents atomic number by 2 and the mass number by 4

Question 13

Polonium-210 decaying to it’s more stable form as lead-206 is an example of what type of decay?

Answer 13

Alpha decay.

it is an alpha-emitter

Question 14

What magnitude of energy do alpha particles emit from the parent nucleus?

Answer 14

High energy.
This energy is quickly lost as the particle travels through matter of air. As a result the particles do not typically travel far, and can be stopped by the outer layers of human skin or a piece of paper.

Question 16

What is beta decay?

Answer 16

There are three types of beta decay: β-, β+, and electron capture. Each type of beta decay involves the conversion of a neutron into a proton, or vice versa, through the action of the week nuclear force.
Beta particles are more dangerous than alpha particles since they are significantly less massive. They therefore have more energy and a greater penetrating ability. However, they can be stopped by aluminum for foil or a centimeter of plastic or glass

Question 17

β- Decay

Answer 17

When an unstable nucleus contains too many neutrons, it may convert a neutron into a proton and an electron (which is also know as a beta- particle) which is ejected.
The atomic number of the resulting daughter nucleus is 1 greater than the radioactive parent nucleus, but the mass number remains the same.
The isotope carbon – 14, the decay of which is the basis of radiocarbon dating of archaeological artifacts, is an example of a radioactive nucleus that undergoes beta- decay
14/6C —–> 14/7C (0/-1 beta is ejected)
This is the most common beta decay so if mentioned on MCAT WITHOUT SPECIFICATION, it’s beta-

Question 17

Electron capture

Answer 17

Another way for an unstable nucleus to increase its number of neutrons is to capture an electron from the closest electron shell (the n=1 shell) and use it in the conversion of a proton into a neutron.
Just like positron emission, electron capture causes the atomic number to be reduced by 1 while the mass number remains the same.
51/24Cr + 0/-1e- —–> 51/23V
(Loses proton because it’s converted into neutron)

Question 18

β+ Decay

Answer 18

Also know as Positron Emission
When an unstable nucleus contains too few neutrons, it converts a proton into a neutron and a positron, which is ejected. This is known as Beta+ decay.
-The positron is the electron’s anti-particle; it’s identical to and electronics at its charge is positive.
–The atomic number of the resulting daughter nucleus is 1 less than the radioactive parent nucleus, but the mass number remains the same.
18/9F—-> 18/8O. (0/+1 beta ejected)

Question 19

Gamma decay

Answer 19

A nucleus in an excited state—which is usually the case after a nucleus has undergone alpha or any type of beta decay— can “relax” to its ground state by emitting energy in the form of one or more photons of electromagnetic radiation. These photons are called Gamma photons (symbolized by gamma symbol y) and have a high frequency and energy.
Gamma photons or gamma rays have neither mass nor charge, and can therefore penetrate matter most effectively. A few inches of lead or about a meter of concrete. Most Scana race there each action from a radioactive Adam changes neither the atomic number nor the mass number of the nucleus.
31/14Si–beat neg. D–> 31/15P*—gamma D–>31/15P+0/0y emitted
* means in excited stage
Alpha and beta decay changes the identity of the element, gamma doesn’t. Gamma decay is simply the expulsion of energy.

Question 20

What happens during gamma decay?

Answer 20

Brings an excited nucleus to a lower energy level, doesn’t change mass number or atomic number.

Question 21

What happens during alpha decay?

Answer 21

Decreases the number of neutrons and protons in large nucleus, subtract 4 from the mass number and subtract 2 from the atomic number.

Question 22

What happens during positron emission?

Answer 22

Increases the number of neutrons, decreases the number of protons, and subtract 1 from the atomic number.

Question 23

What happens during β- decay?

Answer 23

Decreases the number of neutrons, increases the number of protons, and adds 1 to the atomic number.

Question 24

What happens during electron capture?

Answer 24

Increases the number of neutrons, decreases the number of protons, subtract 1 from the atomic number.

Question 25

Americium-241 is used to provide intracavitary radiation for the treatment of malignancies. This radioisotope is known to undergo alpha decay. What is the daughter nucleus?

Answer 25

247Np Alpha decay reduces atomic mass by 4 and atomic number by 2

Question 26

``` Radioactive calcium-47, a known β- emitter, is administered in the form of 47CaCL2 by IV as a diagnostic tool to study calcium metabolism. What is the daughter nucleus of 47Ca? A. 46K B. 47K C. 47Ca+ D. 47Sc ```

Answer 26

D. 47Sc Adds 1 proton and atomic weight doesn't change.

Question 27

Vitamin B12 can be prepared with radioactive cobalt (58Co), a known bet+ emitter, and administered orally as a diagnostic tool to test for defects in intestinal vitamin B12 absorption. What is the daughter nucleus of 58Co? A. 57Fe B. 58Fe C. 59Fe D. 59Ni

Answer 27

B. 58Fe Reduces atomic mass by 1 but atomic weight stays the same

Question 28

A certain radioactive isotope is administered orally as a diagnostic tool to study pancreatic function and intestinal fat absorption. This radioisotope is known to undergo beta- decay, and the daughter nucleus is xenon – 131. What is the parent radioisotope? A. 131Cs B. 131I C. 132I D. 132Xe

Answer 28

B. 131I Since xenon-131 is the daughter we are reversing the process. Instead of adding a proton to atomic number, subtract 1 proton to get the parent.

Question 29

which mode of radioactive decay causes change in the mass number of the parent nucleus?

Answer 29

Alpha decay

Question 30

One of the naturally occurring radioactive series begins with radioactive 238U. It undergoes a series of decays, one of which is: alpha, beta, beta, alpha, alpha, alpha, alpha, alpha, beta, beta, alpha, beta, alpha, beta. What is the final resulting nuclide of the series of decays? A. 204Pb B. 204Pt C. 206Pb D. 206Pt

Answer 30

C. 206Pb Alpha: -4/-2 Beta-: 0/+1

Question 31

What is a half-life?

Answer 31

Different radioactive nuclei decay at different rates. The half-life, which is denoted by t1/2, of a radioactive substance is the time it takes for one-half of some a sample of the substance to decay. Thus, the shorter the half-life, the faster the decay. The amount of radioactive substance decreases exponentially with time.

Question 32

The shorter the half-life....

Answer 32

The greater the decay constant, and the more rapidly the sample decays

Question 33

Cesium-137 has a half-life of 30 years. How long will it take for only 0.3 g to remain from a sample that had an original mass of 2.4 g?

Answer 33

90 years 2.4--30yrs--> 1.2--30yrs--> .6--30yrs-->.3 30x3=90

Question 34

If 58Ca has a half-life of 72 days, approximately what percentage of the radioisotope will still remain in the patient after a year? A. 3% B. 5% C. 8% D. 10%

Answer 34

A. 3% 360 days/72 days=5 half-lives (1/2)^5 equals 1/32 of the original amount administered. 1/32--->3/100 about 3%

Question 35

Iodinated oleochemicals acid, containing radioactive iodine-131, is administered orally to study a patient's pancreatic function. If 131I has a half-life of 8 days, how long after the procedure will the amount of 131I remaining in the patient's body be reduced to 1/5 it's initial value? A. 19 days B. 32 days C. 40 days D. 256 days

Answer 35

A. 19 days 1/5 is between 1/4 and 1/8 1/4=25%=2t 1/8=12.5%=3t So about 2 half-lives occurred, so 8 days times 2 is 16.

Question 36

What is the usual half-life percentages of remaining substance?

Answer 36

``` Time. Amount remaining t(1/2)=1 half-life. 1/2=50% t(1/2)=2 half-life. 1/4=25% t(1/2)=3 half-life. 1/8=12.5% t(1/2)=4 half-life. 1/16=6.25% ```

Question 37

What is an Emission Spectrum?

Answer 37

A glass filled with a small sample of an element in gaseous form. When electric current passed through the glass, the gas begins to glow with a color characteristic of that particular element. If the light emitted by the gas is then passed through the prism, which will separate the light into it's compliment wavelengths Basically shows which wavelengths are emitted by the element. The emission spectrum gives an energetic fingerprint of the element because it consists of a unique sequence of bright lines that correspond with the specific wavelengths and energies.

Question 38

What are the different ways an electron that is in excited say can "relax" or jump back down to ground state (its original state)?

Answer 38

It can either 1) drop down in smaller increments, for example excitation=n=3, drops down to n=2. This will give you the exact energy difference between n=3 and n=2 2) drop down directly to ground state, for example excitation=n=3, drops down to n=1, gives energy difference between n=3 and n=1.

Question 39

What is the equation relating photons (particles of light) that are emitted to their frequencies and wavelengths? (Emission spectrum)

Answer 39

``` E(photon)=hf=c/λ or E(photon)=h x c/λ f=frequencies λ=wavelength h=universal constant called Planck's constant (6.63x10^-34 J*s) C=speed of light ```

Question 40

The Bohr Model of the Atom

Answer 40

By using the emission spectrum, Niels Bohr was able to create a new model, one with energy levels. He theorized that electrons in the atom orbited the nucleus in circular paths, distance from the nucleus was related to the energy of the electrons, and the electrons with greater amounts of energy orbited the nucleus at greater distance. Electrons cannot assume an arbitrary energy but have quantized energy states. By observing the energy spectrum of particular elements, he was able to discern the energy levels of atoms. 1) When the electrons emits the wavelengths passing through, it's dropping back to normal level after excitation. The emission of energy=difference between the two energy levels. 2) The amount of energy that electron absorbs is equal to the amount of energy it takes to be in the energy levels the electron jumps up to due to excitation. (Specific energy corresponds to specific wavelength--able to see this due to color of wavelength once separated in line spectra) *remember this is modeled by Hydrogen

Question 41

Calculating energy level equation

Answer 41

E=(-2.178 x 10^-18)/n^2 Example: E(3-->1)=(-2.178 x 10^-18J)/(1^2) - (-2.178 x 10^-18 J)/(3^2) E(3-->1)= -1.936 x 10^-18 J *Note, the calculation is negative because it is energy being released from the electron. If it is positive, it means the energy is absorbed by the electron.

Question 42

What is a Bohr Atom?

Answer 42

An atom that has only one electron

Question 43

Which of these is NOT an example of a Bohr atom? A. H B. He+ C. Li2+ D. H+

Answer 43

D. H+ Bohr's atom only should have one electron

Question 44

Once you calculate the energy with Bohr's equation, how can you find the wavelength of the photon?

Answer 44

Use E=h x c/λ

Question 45

Are you able to see all electron transitions produced by photons?

Answer 45

No, some you cannot see with the naked eye, but all transitions in an atom will produce photons either in the ultraviolet, visible, or infrared region of the electromagnetic spectrum.

Question 46

What happens to the wavelength if the energy change from one level to another in the atom changes? When the energy change is smaller? When the energy changer is larger?

Answer 46

Wavelength and energy change are inversely related meaning if the energy change is smaller, the wavelength is longer, and when the energy change is bigger, the wavelength is shorter. E=h x c/λ

Question 47

The Quantum Model of the Atom

Answer 47

Is the official model we use to this day because the Bohr model, although it predicted the atomic spectra of one electron atoms accurately, didn't do a good job at predicting the atomic spectra of many-electron atoms accurately. We still believe Bohr's hypothesis that there are energy levels but this model furthers the hypothesis by developing 4 quantum numbers to establish the 'locations' and depict electron interactions more accurately. 4 quantum numbers: shell (n), subshell, orbital, and spin.

Question 48

Quantum Number: What is the Energy Shell (n) of an atom?

Answer 48

Resembles the circular orbitals in Bohr's model. | An electron in the higher shell has a greater amount of energy and a greater average distance from the nucleus.

Question 49

Quantum Number: What is the Energy Subshell of an atom?

Answer 49

This mainly deals with the probability of finding an electron in a certain area, or the shape of the orbital. An orbital describes a three-dimensional region around the nucleus in which the electron is most likely to be found. (Remember, the movement of electrons resembles the movement of waves) A subshell in an atom is comprised of one or more orbitals and is denoted by a letter (s, p, d, f) that describes the shape and energy of the orbital(s). This describes the shape of the orbital The orbitals get progressively more complicated has the energy levels increases. Each energy level contains more subshells as you go higher. For example n=1 has only s while n=2 has both s and p subshells.

Question 50

Quantum Number: What is the Orbital Orientation of an atom?

Answer 50

This mainly deals with how many orbitals (orientations) are in a subshell. The one or more orbitals of the same energy in a subshell are refered to as degenerate orbitals. The number of orbitals increases by 2 with every different orientation/subshell. For example, s subshell only contains 1 orientation while the p subshell as 3 orientations. d has 5 and f has 7

Question 51

Quantum Number: What is the Electron Spin in an atom?

Answer 51

Every electron has two possible spin state, which can be considered the electron's intrinsic magnetism. Because of this every orbital can accommodate up to 2 electrons, with one spin-up and one spin-down. If the orbital is filled, the electrons it holds are "spin-paired."

Question 52

What is Hund's Rule?

Answer 52

Electrons in the same subshell must occupy the available orbitals singly before pairing up. Spins must all be in the same direction.

Question 53

What is the Pauli Exclusion Principle?

Answer 53

No more than two electrons allowed in each orbital.

Question 54

What is Aufbau Principle?

Answer 54

You must fill the lowest energy shell first then work your way up.

Question 55

What is a complete octet?

Answer 55

The noble gases have this, where the eight valence electrons fill the last subshells, making it neutral (or very difficult to create chemical interactions since the elements are content). Accounts for chemical inactivity. Pattern: the eight valence electrons fill in the last (n)s and (n)p (usually it's the first p orbital). All other elements strive for this complete octet.

Question 56

What is a diamagnetic atom?

Answer 56

When all of its electrons are spin-paired. (so must contain an even number of electrons and have all of its subshells occupied. Since all are spin-paired, there is no net magnetic field due to the individual magnetic fields canceling out. Such an atom will be repelled by an externally produced magnetic field.

Question 57

What is a paramagnetic atom?

Answer 57

When it doesn't have all of its electrons spin-paired. They are attracted into externally produced magnetic fields.

Question 58

Periodic Table: What is a group?

Answer 58

Also known as family. It is the vertical column. | -It can tell you where the outermost valence electrons are (which orbital: s, d, p, or f)

Question 59

Periodic Table: What is a period?

Answer 59

It is the horizontal row. | -It can tell you what shell (energy level) the outermost electrons occupy.

Question 60

Periodic Table: In order to tell what shell the electrons of a d-block fill, what do you do with n?

Answer 60

n-1 for example, 4s2 3d1 also refer to the electron filling diagram

Question 61

Are there exceptions to the rules for electron configuration? If so, name examples.

Answer 61

Yes, because some elements can achieve a lower energy state (higher degree of stability) by having a half filled d-subshell. For example, Chromium (Cr, Z=24), you would think its electron configuration would only have four electrons in the d orbital but it would be more stable if it had 5, so it promoted one of its electrons from the s orbital to go up to make it 5. Configuration: Ar 4s1 3d5 Another example: Copper (Cu, Z=29) is actually 4s1 3d10 because it has more stability if d is filled. Other elements that display the same behavior are Mo (molybdenum), Ag (silver), and gold (Au).

Question 62

What is the electric charge of an ion?

Answer 62

It is a nonzero charge.

Question 63

What is an anion?

Answer 63

An atom that has more electrons than protons. | Negative

Question 64

What is a cation?

Answer 64

An atom that has less electrons than protons. | Positive

Question 65

What does isoelectronic mean?

Answer 65

It means that two elements are the same in electron configuration after one of the elements becomes an ion, which changes their electron configuration.

Question 66

How do you calculate the electron configuration of an ion?

Answer 66

Simply move to the right or left of the periodic table to see which element it is isoelectronic with. Right=anion, left=cation

Question 67

Electrons that are removed from the atom, always come from the...

Answer 67

valence shell (these electrons are the first to go)

Question 68

How can calculating the new electron configuration for a transition metal that became an ion be different?

Answer 68

Remember, there is a different order of filling for the d-block. It will lose its electrons from the s block first before it loses from the d because the d block is still higher in energy despite it being on a lower energy level than the s. Example: 4s2 3d2---> 4s1 3d2 (cation)

Question 69

Any electron configuration of an atom that is not as you would assign it, would mean what?

Answer 69

It is in it's excited state. Meaning that one electron was promoted to the next level.

Question 70

Alkali Metals

Answer 70

Group 1 | (n)s1

Question 71

Alkaline Earth Metals

Answer 71

Group 2 | (n)s2

Question 72

Halogens

Answer 72

Group 7 | (n)s2 (n)p6

Question 73

Noble Gases

Answer 73

Group 8 | (n)s2 (n)p6

Question 74

Transition Metals

Answer 74

d-block

Question 75

Representative Metals

Answer 75

s and p blocks

Question 77

Rare Earth Metals

Answer 77

f block

Question 78

The chemical reactivity is determined by the what? | Give examples of each group.

Answer 78

Determined by the electron configuration, or how many valence electrons there are. The noble gases are the most stable because they have a full octet. The Halogens are closer to stability but need one more electron to complete octet. So highly electronegative. You will see them normally in diatomic molecules (covalent bond). When in a compound with another element, they behave as powerful oxidizing agents (gaining electrons). They become stable either as X- anions or sharing electrons with other nonmetals. The alkali metals and alkaline earth metals possess one or two electrons, meaning they want to lose them, behaving as reducing agents in reactions. Generally X+ or X+2 cations.

Question 79

List the Periodic Trends

Answer 79

Shielding, atomic and ionic radius, ionization energy, electron affinity, electronegativity, acidity

Question 80

Periodic Trend: What is shielding?

Answer 80

Each filled shell between the nucleus and the valence electrons shields (or protects) the valence electrons from the full effect of the positively charged protons in the nucleus. (This means it is easier for the atom to lose these electrons or for reactions to occur). This is called nuclear shielding or shielding effect. Where the positive charged pull of the protons is reduced by the negative charges of the electrons in the filled shells. Result: reduction in the positive elementary charge, from Z to Z(eff) (for effective nuclear charge)

Question 81

What are the forces that influence a solitary He atom?

Answer 81

Electrostatic attraction between the electrons and nuclear protons. Electrostatic repulsion between the electrons

Question 82

Periodic Trend: What is atomic and ionic radius and how is it a factor in periodic trend?

Answer 82

Move from left to right (period): atomic radius decreases due to the number of protons increasing across the period but the number of shells remaining the same (only changes in the beginning of each period), so the electrons are being pulled in tighter to the atom due to the greater effective nuclear charge (of the protons). Move down a group: atomic radius increases due to the number of shells increasing making the radius larger and adding more shielding effect so the valence electrons can venture a little more (feeling less effective nuclear charge). Bigger the atom, the easier it loses electrons.

Question 83

What would happen to the radius if you wanted to create an anion? A cation?

Answer 83

Anion: removes electrons, so radius gets bigger (ones that are left are drawn in more closely) Cation: adds electrons, so radius gets smaller X+

Question 84

Periodic Trend: What is Ionization Energy?

Answer 84

The energy it takes to remove an electron.

Question 85

Periodic Trend: What is an atom's First Ionization Energy?

Answer 85

The amount of energy it takes to remove the least tightly bound electron from an atom. Symbol: IE OR IE1

Question 86

Periodic Trend: What is an atom's Second Ionization Energy?

Answer 86

The amount of energy it takes to remove the least tightly bound electron from a cation, X+. IE2 will always be greater than IE1. It takes more energy to remove an electron the second time because the radius for a cation is smaller due to the increase in effective nuclear charge.

Question 87

Periodic Trend: What is the periodic trend for Ionization Energy?

Answer 87

Increases as you go across the table (since the valence electrons are more tightly bound, meaning it takes more energy to get them away) decreases as you go down. Ionization energy for noble gas will always be very large.

Question 88

Periodic Trend: What is Electron Affinity?

Answer 88

The energy associated with the addition of an electron to an isolated atom. It can either be defined as positive or negative. Positive Electron Affinity: energy is required to add an electron. Negative Electron Affinity: energy is released when the electron is added. (meaning the atom as become more stable by adding an electron) Example: Halogens have a large negative electron affinity because adding that one electron will make it an octet making it more stable (releasing energy), but adding an electron to the noble gases or alkali/alkaline earth metals would make them destabilized anions, thus positive.

Question 89

Periodic Trend: What is the periodic trend for Electron Affinity?

Answer 89

Increases in negativity as you go across the table (exception of noble gases) decreases in negativity as you go down a group (exception of noble gases)

Question 90

Periodic Trend: What is Electronegativity?

Answer 90

A measure of an atom's ability to pull electrons to itself when it forms a covalent bond. Basically, it is the greater attraction is has for electrons in a shared bond. This is why the electrons in a compound will tend to be more associated with one atom over another, thus creating the polar covalent bond, the one having the greater electronegativity being polar.

Question 91

Periodic Trend: What is the periodic trend for Electronegativity?

Answer 91

Left to right: increases | Down a group: decreases

Question 92

What is the order of electronegativity for the nine more electronegative elements?

Answer 92

F > O > N > Cl > Br > I > S > C > H

Question 93

Periodic Trend: What is the Acidity of an atom?

Answer 93

The measure of how well a compound donates protons, accepts electrons, or lowers pH in a chemical system.

Question 94

Periodic Trend: What is a binary acid? Stronger acids?

Answer 94

Binary Acid: structure=HX, can dissociate water (HX ----> H+ + X-) Stronger Acids: Result in X- anions that are likely to separate from H+ because they are stable once they do.

Question 95

Periodic Trend: What is the periodic trend for Acidity?

Answer 95

left to right: increases, due to the electronegativity increasing, the acidity increases because the electronegative the anion is, the more acidity is has because it is more stable. (vertical) down a group: increases, due to the increase in size of the atom because acidity also depends on the size of an anion, meaning the greater the size, the more negative charge can be delocalized and stabilized thus the increase in acidity.

Question 96

Of the following, which is the strongest acid? A. H2O B. H2S C. HCl D. HBr

Answer 96

Look at the anions (the second elements listed in the compound) and compare electronegativity and atomic radius. Cl is more electronegative than H2S, so B is eliminated. Br is bigger in atomic radius than both O and Cl, so the answer is D. HBr