CHEM/PHYS

Which of the following electron configurations of beryllium (Be) is incorrect? Select all that apply [Li] 2s2 [H] 1s2 2s2 [He] 2s2 1s2 2s2

1 2 We can abbreviate the electron configuration by placing the last element of the prior row in brackets to represent its electron configuration, and then add the configuration of the valence electrons from the periodic table. Hydrogen [H] is not the last element from the prior row, so it should not be in brackets.

Which of the following does an absorption spectrum depend on? Select all that apply. the specific element. the movement of electrons from lower energy levels to higher energy levels. the movement of electrons from higher energy levels to lower energy levels. none of the above

1 2 Atomic emission and absorption spectra are unique for each element.

Which of the following are NOT reactions? Select all that apply. Liquid water freezing. Liquid water boiling. Ammonia decomposing into nitrogen and hydrogen. Ethanol evaporating

1 2 4

What happens when an electron jumps from shell n = 1 to shell n = 2? Select all that apply. the electron becomes excited a photon is emmitted energy is absorbed the electron moves to a more stable state

1 3

Which of the following elements have 10 electrons in their d subshell? Select all that apply. Zinc palladium silver roentgenium (Rg)

1 3 4 zinc is [Ar] 4s23d10. silver is [Kr] 5s14d10. (Rg) is [Rn] 7s15f146d10 Half-filled and fully-filled are more stable than subshells with any other number of electrons. So, a p subshell is especially happy with 3 or 6 electrons, and a d subshell is especially happy with 5 or 10 electrons, and so forth. This means there are a few exceptions to the Aufbau principle for electron configuration, particularly in the chromium and copper columns of the periodic table. Thus, copper has an electron configuration of [Ar] 4s13d10 because the 3d subshell steals an electron from the 4s orbital. Roentgenium is in the same column as copper, so it will follow the same principle.

Which of the following are binary compounds? Select all that apply. NaCl H2 PbSO4 CaCl2

1 4

Which of the following statements are true about ammonium nitrate (NH4NO3)? Select all that apply. The ammonium ion is the cation and the nitrate ion is the anion. The ammonium ion is the anion in the nitrate ion is the cation. ammonium nitrate has covalent bonds only ammonium nitrate has both ionic and covalent bonds

1 4

How many total valence electrons does hydrogen peroxide (H2O2) have?

14 To calculate the total number of valence electrons, take the sum of the valence electrons of each atom in the molecule. Hydrogen peroxide has two hydrogens (1 valence electron each) and two oxygens (6 valence electrons each), for a total of 1 + 1 + 6 + 6 = 14.

Which of the following atomic symbols represent ferrous and ferric ions, respectively? Fe2+ and Fe3+ Fe3+ and Fe2+ Fe3+ and Fe+ Fe2+ and Fe+

1st ferric = eric = three, all have Es If a given element can be found in the form of more than one different cation, its charge will be indicated by a superscript numeral as in Fe2+ and Fe3+ or using Roman numerals as in iron(II) oxide vs. iron(III) oxide. Another option is for the ion with the lesser charge to have the suffix -ous and the ion with the greater charge with the suffix -ic as in ferrous ion and ferric ion.

Which term is correctly defined? The atomic number Z is the average number of protons and neutrons in an atom accounting for all known isotopes. The molecular weight is the total weight of two or more bonded atoms

2

How would 5 electrons be arranged in a p subshell? 3/5 electrons will share 2 orbitals w opposite spins. 2 electron pairs will occupy two orbitals, and the remaining electron will bein the third orbital

2 According to Hund's rule, one electron fills each orbital of a given subshell with parallel spin until each is half-filled, and then they begin sharing orbitals, or pairing, with another electron until the orbitals of that subshell are all filled. In this case, the first 3 electrons will each occupy their own orbital and the remaining two electrons will pair with an electron in the first two orbitals. This leaves two of the orbitals completely filled with two electrons each and the third orbital half-filled with one electron.

Single displacement reaction. Double displacement reaction. Precipitation reaction. None of the above.

2 3 Since each cation and anion switches the ion to which it is bound, this is a double displacement reaction. Precipitation reactions involve the formation of a solid (an insoluble compound) from aqueous ions. Since solid lead bromide forms during the process shown above, this is a precipitation reaction as well.

What happens when an electron jumps from shell n = 2 to shell n = 1? Select all that apply. that electron becomes excited a photon is emitted energy is absorbed by the electron the electron moves to a more stable state

2 4

Which of the following statements accurately describes Ca2+? Select all that apply. (Refer to the periodic table if necessary.) 20 protons 20 neutrons and 20 electrons. Mass number is 40 AMU. It has two fewer neutrons than CA. It has 20 protons and 18 electrons

2 4

Which statement is true regarding ionic bonds? Ionic bonds refer to bonds between atoms such as oxygen and hydrogen due to its significant electronegativity difference. Barium hydroxide or BaOH2 contains two ionic bonds

2 Barium is a metal, while oxygen and hydrogen are nonmetals. The barium is connected to two oxygen molecules through two separate ionic bonds.

How can the electron configuration of Na+ be described compared to Na? The electron configuration of NA plus will have one fewer electron in the 2p orbital. The electron configuration of NA plus will have one fewer electrons in the 3s orbital period

2 Neutral sodium has an electron configuration of [Ne] 3s1, while Na+ has an electron configuration identical to that of neon (Ne). This means that there is one fewer electron in the 3s orbital. When forming an ion, we always add or remove electrons from the subshell with the highest energy level.

The following molecule is nitrogen triiodide, a highly explosive compound. Yes there is no charge on the nitrogen. Yes there are eight electrons surrounding the nitrogen. No there is no charge on the nitrogen.

2 Nitrogen has achieved its octet and there are eight valence electrons. There is a lone pair of electrons as well as three shared pairs (two electrons with each iodine).

How many protons, neutrons, and electrons are in 39Ca2+? 19 P, 19 N, 17 E 19 P, 20 N, 18 E 20 P, 21 N, 17 E 20 P, 19 N, 18 E

20 P, 19 N, 18 E 39Ca2+ is a charged isotope of calcium. Its mass number is 39, and it contains 20 protons by definition; therefore, it has 19 neutrons. The number of electrons listed is correct. Neutral calcium has 20 electrons because there are 20 protons. Therefore, Ca2+ will have two fewer electrons than protons.

Which set of three quantum numbers is consistent with a valence electron configuration that could contain an electron described by the given set? n=2, l=1m ms=+1/5, 2s1 n=4, l=2, ms=-1/2, 4s2 3d6

2nd The first quantum number, the principal quantum number (n), describes an electron's "shell", the average relative distance from the nucleus. The second quantum number (l) describes the subshell, s (0), p (1), d (2), or f (3). The quantum number ms indicates spin, which is either spin up (+½), with the electron aligned with a magnetic field, or spin down (-½), with the electron aligned against it. Recall that electrons first fill orbitals with their spins up, and then pair with their spins down. The designation n = 4, l = 2, ms = -½ could be the sixth d electron in 4s23d6. There are five d orbitals so the sixth is spin down, as are four other d electrons that also have these same quantum numbers.

Which of the following are possible values for angular momentum quantum numbers in the n = 4 shell? +1/2, -1/2 0, 1, 2,3

2nd. The angular momentum quantum number (l), also called the azimuthal quantum number, describes the shape of the orbital. This tells us what subshell the electron is located in within a shell, where L can range from 0 to n-1 for a given principal quantum number. A shell of n = 4 will have angular momentum quantum numbers 0 to 3 which includes 0, 1, 2, and 3.

In liquid chromatography, a mobile phase contains various low molecular weight organic solutes identified as an alcohol (ROH), a secondary amine (R2NH), and an alkyl halide (RCl). The solutes are run through a stationary phase that has primary amine (RNH2) groups. Assuming no solvent interaction with the stationary phase, arrange the solutes by their order of elution from first to last ROH, R2NH, RCl R2NH, ROH, RCl RCl, R2NH, ROH RCl, ROH, R2NH

3 The solute that will elute first is the one that has the weakest interaction with the stationary phase. The alkyl halide will have no hydrogen bonds with the amine, so it will be the first to elute. The secondary amine can form a hydrogen bond to the primary amine that is a component of the stationary phase, but the alcohol will form a stronger hydrogen-bonding interaction with the stationary phase because of its greater polarity. Consequently, the secondary amine will be second to elute and the alcohol will be the last to elute from the column.

How many orbitals exist for a shell of n = 2? 4 9 3 18

4 A shell of n = 2 consists of 0 to n-1 subshells. The subshells are the l = 0 (s subshell) and l = 1 (p subshell). The s subshell contains a single orbital, 0. The p subshell contains 3 orbitals: ml = -1, 0, +1. The total number of orbitals equals 4.You can find the number of orbitals by squaring the shell number: 22 = 4.

Al is a reducing agent Al is oxidized in the reaction Fe is an oxidizing agent O is reduced in the reaction

4 The oxidation state of oxygen does not change in this reaction.

Which of the following situations would NOT occur under the Pauli exclusion principle? one electron in the 4s subshell and 5 electrons in the 3d subshell four electrons in the 2p subshell an electron in the 1s subshell with positive half spin and the other w neg half spin 2 electrons in the 1s subshell w positive half spin

4 According to the Pauli exclusion principle, no two electrons in a given atom can have the exact same four quantum numbers. Two electrons in the 1s subshell with positive half spin would have the exact same four quantum numbers: 1, 0, 0, +1/2.

How many electrons does beryllium need to fill its valence shell?

4 Beryllium is an exception to the octet rule. To completely fill its valence shell, it only needs four electrons.

For oxygen, name its # valence E atomic # mass # molecular weight found in nature

6 valence atomic # 8 16 amu 32 amu

How many electrons can the n = 2 shell hold? 4 8 16 32

8. The n = 2 shell is made up of the s subshell and p subshell. The s subshell has one orbital that can hold 2 electrons. The p subshell has 3 orbitals (-1, 0, +1) that can each hold two electrons for a total of 6 electrons. This means there are a total of 8 electrons in the n = 2 shell.

Which of the following molecules would be expected to have the smallest overall dipole? CF4 CHF3 CH2F2 CH3F

Carbon tetrafluoride (CF4) has no overall dipole because the dipoles of each C-F bond are arranged symmetrically in a tetrahedron and cancel each other out.

Alkali metals, when placed in water, are highly reactive and sometimes capable of causing large explosions. Which property can explain this reactivity? Alk metals have 7 valence electrons Alk metals readily accept electron Alk metals are catalysts in combustion rxns Alk metals tend to form cations

Cations Members of the alkali metals have one valence electron. When this electron is lost, these elements become a cation with a noble gas configuration, making them very stable. For this reason, alkali metals can lose an electron extremely easily, making them highly reactive in water.

Which of these names is correctly associated with the chemical formula shown? Ferrous chloride FeCl3. Chlorite ClO2(1-) Nitrate NO3(1-) Sulfate S03(2-)

Chlorite ClO2(1-) For oxyanions, "-ite" is used as the suffix for anions with fewer oxygen atoms and "-ate" is used as a suffix for anions with more oxygen atoms. Chlorate is ClO3-, and chlorite is ClO2-. (Remember that "per" means even more oxygens, e.g. perchlorate is ClO4-; and "hypo" means even fewer, e.g. hypochlorite is ClO-.)

Arrange the following intermolecular and intramolecular forces from strongest to weakest. IONIC BONDS DIPOLE-DIPOLE HYDROGEN ION DIPOLE LONDON DISPERSION

IONIC ION-DIPOLE HYDROGEN DIPOLE-DIPOLE LONDON DISPERSION

Which of the following best describes a nitrogen atom after it has lost a proton? Nitrogen becomes an isotope with a mass number that has decreased by one AMU. The molecular weight of nitrogen decreases by one AMU. Nitrogen becomes carbon 12. Nitrogen becomes carbon 13

N13 When nitrogen loses one proton, it will become an isotope of carbon, but that carbon will still have 7 neutrons, which is the same number of neutrons in nitrogen. Seven neutrons plus six protons is equal to a mass number of 13, making this atom carbon-13.

Which of the following elements have 4 electrons in their d subshell? Select all that apply. Mn Pd Au none

None of the answer choices listed have 4 electrons in their d subshell. The electron configuration of gold is [Xe] 6s14f145d10. Half-filled and fully-filled are more stable than subshells with any other number of electrons. So, a p subshell is especially happy with 3 or 6 electrons, and a d subshell is especially happy with 5 or 10 electrons, and so forth. This means there are a few exceptions to the Aufbau principle for electron configuration, particularly in the chromium and copper columns of the periodic table. Thus, copper has an electron configuration of [Ar] 4s13d10 because the 3d subshell steals an electron from the 4s orbital. Gold is in the same column as copper, so it will follow the same principle.

why is this not a synthesis HCO3(-) + H(+) --> H2CO3

This reaction shows the protonation of bicarbonate to carbonic acid, not the synthesis of carbonic acid. Protonation as such is usually reversible, and the reactants and products exist in equilibrium - both of which are uncharacteristic of synthesis reactions.

True or false: All noble gases have eight valence electrons.

This statement is false. While all noble gases do have a completely filled valence shell, helium only has two valence electrons. Below helium, all noble gases have eight valence electrons.

What is Zeff = effective ____ charge Which of the following would increase the Zeff of an atom? Select all that apply. More protons in the nucleus Less protons in the nucleus More non-valence electrons Fewer non-valence electrons so then...Zeff increases across which directions on the periodic table? down left down right up right up left Which of the following ions has the largest radius? Cl- K+ S2- Ca2+

Zeff = effective nuke charge = how much valence electrons feel the pull of protons in the nucleus 1st and last options right up When you move across a period, atomic number goes up, which means that the number of protons in the nucleus goes up, increasing Zeff. When you move down a period, however, the shielding effect and the distance between the nucleus and the valence electrons goes up, causing the force on the valence electrons to go down. For this reason, Zeff goes down as you move down the periodic table, despite the increasing charge of the nuclei.

what is the correct electron configuration for molybdenum

[Kr] 5s14d5. Exceptions to the classic rules of electron configuration stem from the idea that half-filled and fully-filled subshells are more stable than subshells filled with some other number of electrons. For a p subshell, it is energetically favorable to contain either three or six electrons; similarly, a d subshell will be stable if it contains either five or ten electrons. The exceptions to understand for the MCAT® are the transition metals in the same groups or columns as chromium (Cr) and copper (Cu). Specifically, these constitute exceptions to the Aufbau principle.

What is the electron configuration of Mg2+? [Ne] [Ne]3s2

[Ne] Mg2+ has two fewer electrons than neutral magnesium, giving the cation form the same electron configuration as neon (Ne). We can abbreviate the electron configuration by placing the last element of the prior row in brackets to represent its electron configuration, and then add the configuration of the valence electrons from the periodic table. Mg2+ has lost its two valence electrons, so there is nothing to follow [Ne].

Which of these elements has the greatest first ionization energy, IE1? Sodium sulfur chlorine magnesium

chlorine All of these elements are in the third row of the periodic table. More energy is required to remove an electron that is closer to the positive nucleus. Therefore, ionization energy generally increases as the atomic radius decreases from left to right across a period, and decreases as the radius increases moving down a group. Thus, chlorine should have the greatest IE1. For the elements listed the correct order for increasing ionic energy is sodium<magnesium<sulfur<chlorine. Corresponding actual values in kJ/mol are: 496, 738, 1000, 1251. (Note: The additional stability associated with filled and half-filled shells, though, affects this general trend. For example, IE1 for phosphorus, with its half-filled valence shell, is greater than that of sulfur due to the greater stability of phosphorus' half-filled p subshell.

Order the following subatomic particles from smallest to largest mass. If a tiebreaker is needed, list the subatomic particle with the largest charge first. proton neutron electron

electron proton neutron

Which of the following is true about the energy associated with an electron moving from orbital n = 5 to n = 2? (Note, R = 2.18 x 10-18J) 4.6x10^-19 is absorbed/emitted

emitted

In which of the following molecules has the central atom achieved a complete octet? Select all that apply. methane ammonium sulfur trioxide carbon dioxide water

everything except for 3

True or false: H2SO4 is a polyatomic ion.

false. A polyatomic ion is a charged species consisting of multiple atoms bonded together. H2SO4 is not charged, so it is not categorized as a polyatomic ion.

True or false: During an MCAT® exam, the fastest way to determine an atom's formal charge is by counting up the relative number of electrons and protons it contains.

false. During a timed exam, formal charge should be calculated as the number of valence electrons an atom "should" have (according to the periodic table) and the number it actually has. Thus, formal charge can be quickly determined by counting the number of valence electrons and bonds made to other atoms.

True or false: The number of electrons in an orbital can vary depending on the subshell the electron is in.

false. Each orbital can hold up to two electrons, regardless of the energy level, subshell shape, or subshell orientation.

True or false: Free radicals are highly reactive because they have more electrons than their valence shells can hold stably.

false. Free radicals are compounds that have an odd number of valence electrons and so have an unpaired electron in their structure. This unpaired electron makes these compounds highly unstable.

True or false: π bonds have a small area of directly overlapping electron density, form double bonds, and are stronger than σ bonds.

false. In sigma bonds, there is a relatively large area of directly overlapping electron density compared to pi bonds, which occur between two parallel p orbitals and are weaker than sigma bonds. Single bonds between two atoms are made of sigma bonds, while double bonds are one sigma bond and one pi bond, and triple bonds are one sigma bond and two pi bonds. Therefore, double bonds are indeed stronger than single bonds, but that is because they have both a sigma bond component and a pi bond component. In a direct comparison, sigma bonds are stronger than pi bonds.

True or false: Ion-dipole interactions require a metal and a non-metal.

false. Ion-dipole interactions can take place between any ion and a dipole, not requiring a metal to be involved. Note that ion-dipole interactions are an intermolecular force; do not confuse them with ionic bonds, an intramolecular force that typically forms between a metal and non-metal.

True or false: Covalent bonds always form between metals and nonmetals.

false. Ionic bonds form between metals and nonmetals. Covalent bonds form between atoms with more similar electronegativity values, often two nonmetals, such as carbon bonding with carbon or carbon binding with hydrogen.

True or false: Covalent bonds must involve two chemically distinct atoms sharing electrons with each other.

false. Nonpolar covalent bonds can form between two atoms of the same element (e.g., O2) and a single atom can donate both electrons in coordinate covalent bonds. An example of a coordinate covalent bond is the additional N-H bond in NH4+ or ammonium, formed from ammonia and a hydrogen ion.

True or false: Formal charge values allow the actual charge on a given atom within a molecule to be determined.

false. While sometimes formal charges correspond to actual charges, they don't always. The reason for this discrepancy is that formal charge calculations assume that electrons are evenly shared between atoms that are covalently bonded with each other. In reality, due to differences in electronegativity, this is not the case. Many compounds without formal charges will have strong partial charges distributed through the molecule.

True or false: Looking at a molecule's formal charge can provide a snapshot of the distribution of partial charges throughout a molecule.

false. While sometimes formal charges correspond to actual charges, this is not always the case. The reason for this discrepancy is that formal charge calculations assume that electrons are evenly shared between atoms that are covalently bonded with each other. In reality, due to differences in electronegativity, this is not the case. Many compounds without formal charges will have strong partial charges distributed throughout the molecule.

Which of the following situations could occur under the Pauli exclusion principle? Select all that apply. One electron in the 4s subshell and five electrons in the 3d sub shell. Four electrons in the 2p sub shell. An electron in the 1s subshell with positive half spin and the other with a negative half spin. Two electrons in the 1S sub shell with positive half spin

first 3

What is the electron configuration of beryllium (Be)? Select all that apply. [Li]2s2 [H]1s2 2s2 1s2 2s2

last Beryllium has 4 protons, as indicated by its atomic number, so neutral beryllium should have 4 electrons. This is the only answer choice that accounts for 4 electrons and is written in proper notation.

Which of the following orbitals cannot exist in an s subshell? Select all that apply. 0 -1 +1 +2

last 3 The magnetic quantum number, ml, ranges from -l to +l for a given subshell. The s subshell (l = 0) has just 1 orbital, so ml = 0. Thus, there is only one possible orientation in space for this subshell.

Which of the following statements could be true according to the Heisenberg uncertainty principle? Select all that apply. an electron is located at coordinates x y z travelling at 800 m/s electron is located at coordinates x y z travelling at an unknown velocity an electron is travelling at 800 m/s from an unknown location an electron is most likely located in the d orbital as it travels at 800 m/s

last 3 According to the Heisenberg uncertainty principle, it is impossible to precisely know both the exact location and the exact momentum of an electron at any given moment in time. In this case, we know the precise location of the electron represented by coordinates x, y and z, but we know very little about its velocity. In this case, we know the precise velocity of the electron, but we know very little about its precise location. In this case, we know the precise velocity of the electron, but we cannot know its precise location. All we know is roughly which orbital the electron is in.

Alkali metals are characterized by which of the following? Select all that apply. Reactivity w water Ability to donate an electron Ability to be pulled into a wire A single valence electron in their ground state

literally all of them

The law of conservation of ______ dictates that atoms appearing in the reactants must appear in the products as well; the law of conservation of ______ dictates that the charges must balance on either side of a reaction. mass; energy energy; mass energy; energy mass; mass

mass; mass The law of conservation of mass states that mass in an isolated system is neither created nor destroyed; as a result, any atom appearing in the reactants must be accounted for in the products. The law of conservation of mass applies not just to mass, but also to charge. This means that the net charge on each side of a chemical equation must also balance out.

Which element has the highest effective nuclear charge? Boron Carbon Nitrogen Oxygen Of the atoms listed below, which will have the largest atomic radius? K K+ Mg Mg2+

most amount of protons, highest nuke charge K, fattest atoms down and left of periodic table. Not K+ bc it has more protons than electrons, so protons will pull eelctron cloud closer making the atom not as fat

What happens to fluorine when it gains a proton? it becomes a new isotope. becomes a cation. it becomes a new element

new element New elements are formed when an atom loses or gains a proton.

What is the electronic geometry of water? linear bent trigonal pyramidal tetrahedral

tetrahedral Water has two lone pairs and two single bonds, which makes its electronic geometry tetrahedral.

A period is at the end of a horizontal sentence. Therefore a group is... Which of the following elements are found in the same group? Select all that apply. Boron Carbon Nitrogen Phosphorous Arsenic

the column on the periodic table Nitrogen Phosphorous Arsenic

True or false: Ionization energy refers to the energy required to free a valence electron from an element.

true

True or false: When filling orbitals, electrons will first spread out to fill every orbital in the subshell with one electron per orbital.

true. According to Hund's rule, electrons fill each orbital in a given subshell with parallel spin to one another until each is half-filled. Afterwards, electrons share orbitals or pair with another electron until the orbitals of that subshell are all filled.

Place the following molecules in order of highest to lowest boiling point in an aqueous solution. Ethanol (C2H6O) Hexane (C6H14) Water (H2O)

water (highest bp), ethanol, hexane Boiling point is largely determined by intermolecular forces such as hydrogen bonding and London-dispersion forces. Water contains two sites of hydrogen bond donation as well as acceptance, so it will have the highest boiling point of the options provided. Ethanol is smaller than hexane, but its ability to hydrogen bond will mean its boiling point is higher than hexane. Hexane is nonpolar and has the weakest intermolecular forces.

is this pairing correct K; [Ar] 4s1

yer. Potassium is [Ar] 4s1. We can abbreviate the electron configuration by placing the noble gas of the prior row in brackets to represent its electron configuration, and then add the configuration of an element or ion's valence electrons following the periodic table. The noble gas preceding potassium (K) in the prior row is argon (Ar), so we can put [Ar] in brackets. Potassium (K) is in the fourth row (n = 4) and is in Group 1, so it has 1 valence electron. Its abbreviated electron configuration is therefore [Ar] 4s1.

Which of the following is the correct identification of ZnO2? zinc oxide zinc (II) oxide zinc dioxide zinc (IV) oxide

zinc (IV) oxide. For transition metals, we must specify the oxidation number of the metal using Roman numerals. This tells us how many electrons the transition metal has lost. The oxidation number of oxygen is -2 and there are two of them, giving oxygen a -4 total oxidation state. Thus, zinc must have a +4 oxidation state or (IV) Roman numeral to balance the overall molecule to neutral.