MY Chemistry Workshops and Quizzes
How many valence electrons does phosphorous have?
Answer: 5
How many electrons may occupy the shell n = 2?
Answer: 8 No more than 2n^2 electrons will occupy the n=2 shell. So the maximum number of electrons is 2(2)2 = 8.
diamagnetic
Atoms, ions, or molecules with all paired electrons are diamagnetic.
ml Values (Magnetic Quantum Number)
For any given subshell, mcan have integer values ranging from -l to +l.
Hund's rule
Hund's rule tells us where the three electrons in the partially filled 2p subshell will go; each electron has a parallel spin and occupies a different orbital.
Alkali Metals Group
I
Alkaline Earth Metals Group
II
ms
Spin Quant. Number The value of ms can be either +1/2 or -1/2.
What is the electron configuration of phosphorous?
The correct answer is: 1s^2 2s^2 2p^6 3s^2 3p^3.
What is the electron configuration of oxygen?
The correct configuration is: 1s^2 2s^2 2p^4. Oxygen, O, is the eighth element, so it must have eight electrons.
Halogens Group
VII
electron configuration for chromium
[Ar] 3d5 4s1
Which species is the reducing agent in the following reaction? 2Na(s) + 2H2O(l) --> 2NaOH(aq) + H2(g) A. Na B. H+ C. H2O D. OH-
A. Na The reaction shown is an oxidation-reduction reaction. In redox reactions, the reducing agent is the species that is oxidized, or has lost electrons. The solid sodium is oxidized to the +1 state in NaOH from a neutral state. Sodium is oxidized in the reaction, so it is the reducing agent.
ATOMIC THEORY AND BONDING QUIZ ↓
ATOMIC THEORY AND BONDING QUIZ ↓
What is the abbreviated form of the electronic configuration of phosphorous?
[Ne]3s^23p^3
Which will fill first, the 4f subshell or the 5p subshell?
5p *USE N+L VALUES!* *The 5p subshell fills before the 4f subshell because the 5p subshell is lower in energy. Comparing the (n + l) values, the 4f has (4 + 3), or 7, and the 5p is (5 + 1), or 6.*
Four Quantum Numbers
-principal quantum number (n) -azimuthal quantum number (l) -magnetic quantum number (ml) -spin quantum number (ms)
Subshell shapes
0-->s; sphere 1-->p; dumbbell 2-->d; clover
Which subshell is higher in energy, or d, assuming the same n value? A. p B. d
B. d Only the quantum numbers n and affect the energy of an orbital. A orbital has a smaller value of ( = 1) than a d ( = 2) orbital does, so the orbital will be lower in energy than the d orbital. The relative energies of orbitals will be discussed more when we get to the electronic configurations of atoms.
Aluminum reacts with oxygen to yield aluminum oxide. Which of the following elements, if reacted with oxygen, will most likely yield compounds whose properties are most similar to aluminum oxide? A. Silicon B. Sodium C. Gallium D. Germanium
C. Gallium Elements in the same column of the periodic table tend to have similar reactivities because they have the same number of valence electrons. We are looking for an element that is in the same group as aluminum in the periodic table, group III. Choice (A), silicon, is group IV. Choice (B), sodium, is group I. Choice (C), gallium, is group III, along with aluminum. And choice (D), germanium, is group IV.
Which of the following is diamagnetic? A. V B. Nb2+ C. Zn D. Ni2+
C. Zn If we look at the electron configuration of each atom or ion listed, zinc is the only species listed which is diamagnetic. The configuration of V is [Ar]4s23d3. V has an odd number of valence electrons, so it is paramagnetic. The configuration of Nb2+ is [Kr]4d3. Nb2+ also has an odd number of valence electrons. Zn has a configuration of [Ar]4s23d10. All the electrons are paired, so Zn is diamagnetic. The configuration of Ni2+ is [Ar]3d8. (Remember to remove electrons from the 4s shell before the 3d.) The eight d electrons fill like this: . There are unpaired electrons, so Ni2+ is paramagnetic. Thus, from the given choices, only Zn is diamagnetic and answer choice (C) is the correct response.
When an atom goes from its ground state to an excited state A. the number of core electrons must decrease. B. the number of valence electrons must decrease. C. the total energy of the electrons must increase. D. the total energy of the electrons must decrease.
C. the total energy of the electrons must increase. (C) According to the quantum mechanical model, atoms in the ground state have their electrons in the lowest energy configuration, each occupying the lowest energy orbital that it could under the constraint of the Pauli exclusion principle. Upon absorbing energy, one or more of the electrons will get promoted into an orbital of higher energy, increasing the energy of the electronic configuration. This does not involve the necessary loss of the electron in question (although it could), which eliminates choices A and B. (The number of core electrons could also in principle decrease if a core electron is excited to the valence level, but again, this is not a requirement for excitation.)
Mn 2+ : How to remove electrons from subshell?
Manganese typically forms the Mn2+ ion. The electrons are removed first from the 4s orbital, so the electron configuration of Mn2+ is [Ar]3d^5. In the example of Mn2+, the 3d orbital is half-filled (the d orbital holds a maximum of ten electrons). On Test Day, you may forget which oxidation state transition metals ions have, so remember that half-filled and full shells contribute to the stability of ions. For example, cadmium, Cd, a transition metal located in the fifth period, typically forms the Cd2+ ion. The Cd+ and Cd3+ ions are rare; let's work through why this is so. The electron configuration of Cd is [Kr]5s24d10. Loss of two electrons from the 5s orbital would result in a very stable outer electron configuration of 4d10 (a fully-filled d orbital). Loss of one electron and three electrons to form the +1 and +3 ions, would result in the less stable electron configuration of [Kr]5s14d10 and [Kr]4d9, respectively.
QUANTUM NUMBER WORKSHOP ↓
QUANTUM NUMBER WORKSHOP ↓
Pauli Exclusion Principle
The Pauli Exclusion Principle states that no two electrons in an atom can have the same four quantum numbers.
What are the quantum numbers that could define an outer valence electron of Co3+? Only image
The electron configuration of Co is [Ar]4s^2 3d^7. When Co forms the Co3+ ion, its electron configuration becomes [Ar]3d^6. Hence, an outer valence electron is in the 3d orbital. Then n = 3 and = 2. Only one choice has these quantum numbers listed, choice (A).
Which zinc ion is most likely to form? A. Zn+ B. Zn2+ C. Zn3+ D. Zn4+
The electron configuration of zinc is [Ar] 4s23d10. If zinc loses an electron, it will be removed from the 4s shell first. Removing one electron will leave an unpaired electron in the 4s shell, which is not very stable. Removing two electrons leaves a full d shell, which is rather stable. In fact, zinc ion exists almost always as the Zn2+ ion. Thus, choice (B) is the correct answer. Removing more than two electrons would result in an unfilled d shell and is not very stable.
What determines the shape of a subshell?
The value of "l" determines the shape of the subshell.
Noble Gases Group
VIII
How many orbitals and electrons are there in the d subshell?
orbitals = 5 electrons = 10 For a d subshell, there are five values of ml (remember the 2l + 1 rule). These values, -2, -1, 0, +1 and +2, correspond to the orbitals dxy, dxz, dyz, dx2-y2 and dz2. Two electrons can occupy each of these orbitals, for a total of ten electrons in the d subshell. In general, the maximum number of electrons in any subshell is 4l + 2.
Which element has the most metallic character? (Table on the quiz)
Answer from me: Element with N=1 , 2e ; N=2 8e ;N=3 1e. (A) Elements that have one electron is their ns valence shell belong to the alkali metals, Group IA. This group lies to the far left of the periodic table, and the elements in this group are the most metallic; therefore, Element A is the most metallic, and choice A is the correct response. Element B is considered metallic, but it lies farther to the right of the periodic table and can exhibit nonmetallic behavior; therefore, choice B can be eliminated. Element D is a nonmetal, so choice C can be eliminated. Finally, choice D can be eliminated because element E has a full shell: It is a noble gas and not a metal.
Which element is most inert? (Table on the quiz)
Answer from me: Element with N=1 , 2e ; N=2 8e ;N=3 8e.
If an atomic electron has an l-value of 3, what are the possible values for ml ?
Answer: -3, -2, -1, 0, +1, +2, +3 Do you see a pattern in the above examples? When = 0, there is 1 possible value for ; when = 1, there are 3 possible values for ; when = 3, there are 7 possible values for . In general, for any value of , there will be 2 + 1 possible values for .
What is the electron configuration of Cl-?
Answer: [Ne]3s^2 3p^6 The electron configuration of Cl is [Ne]3s^2 3p5. Cl- has one additional electron, which is added to the 3 orbital, giving [Ne]3s^2 3p^6.
paramagnetic
Atoms, ions, or molecules with unpaired electrons are paramagnetic.
How many protons are in the nucleus of an atom with atomic number 20? How many electrons surround the same atom?
How many protons are in the nucleus of an atom with atomic number 20? How many electrons surround the same atom? Number of protons = 20 Number of electrons = 20 Remember, the number of electrons always equals the number of protons in a neutral atom. Because the elements in the periodic table are arranged by increasing atomic number, we can also say that the elements are arranged by increasing number of electrons. The rows are the periods from which the table gets its name. The period indicates the highest energy level, hence the highest principal quantum number, occupied by electrons of elements in that period. The shape of the periodic table can help you remember electron configurations and the order in which orbitals are filled.
If an electron of an atom is excited from one orbital to another, it could make which of the following transitions? A. 4f to 6s B. 3p to 4s C. 5p to 5s D. 4s to 3s
If an electron is said to be "excited" from one orbital to another, it must have gained energy and ended up in an orbital of a higher energy state than the one in which it began. Looking at the choices, we can use the *(n + l )* rule to determine the relative energies of the choices listed. Remember the numbers that the values correspond to: l= 0 is s, l= 1 is p, l= 2 is d, and l= 3 is f. In (A), n = 4 and l= 3, so (n + l) is 7, and the electron is being promoted to an (n + ) value of (6 + 0), or 6. This is a move down in energy. In (B), the electron is moving from a lower energy level to a higher energy level; both (n + ) values are 4, but 3p has a lower n value than 4s, so it is lower in energy. In both (C) and (D), the electron is moving from higher energy to lower energy, from 6 to 5 and 4 to 3, respectively.
If n = 2, what are the possible quantum numbers that define the depicted atomic electron? (Dumbbell picture with one arrow up on one side of the dumbbell)
n = 2 l= 1 ml = -1, 0, or 1 ms = +1/2 or -1/2
What are the principal and azimuthal quantum numbers for an electron in a 4f shell?
n=4 and l=3 spdf=0123
IONIZATION ENERGY QUESTION
(C) Even without being familiar with the chemistry of the Group IA elements, you could have eliminated choices A and D because removing an electron from a positively-charged species always requires more energy than the removal of an electron from a neutral species. Atoms always lose or gain electrons in an attempt to form a noble gas core. Since all alkali metals contain one electron in their ns valence shell, they are easily ionized to form cations with a single positive charge, so the first ionization energy is quite low. These cations now have both a positive charge and a stable noble gas core, which makes it extremely difficult to remove another electron; therefore, the second ionization energy is significantly higher than the first ionization energy (choice B can be eliminated and choice C is the correct response).
What is the electron configuration of Cr 3+?
1s^2 2s^2 2p^6 3s^2 3p^6 4s^0 3d^3 Loses two 3d and one 4s
What is the ground-state electron configuration of Co (atomic number 27)? A. 1s22s22p63s23p63d74s2 B. 1s22s22p63s23p63d84s1 C. 1s22s22p63s23p63d9 D. 1s22s22p63s23p63d64s3
A. 1s22s22p63s23p63d74s2 (A) Cobalt has an atomic number of 27, so in its neutral form, it must possess 27 electrons. Remember the Aufbau or building-up principal: electrons fill orbitals in such a way that the atom is in its lowest energy configuration. Also remember the Pauli exclusion principle: no two electrons can have the same four quantum numbers; therefore, an s subshell can hold a maximum of 2 electrons (choice D can be eliminated), a p subshell can hold a maximum of 6 electrons, and a d subshell can hold a maximum of 10 electrons. The first energy orbital is the 1s orbital, which can hold a maximum of 2 electrons. The next orbital that is filled is the 2s orbital, which again holds two electrons, followed by the 2p orbital, which holds six electrons. The n = 3 shell has three subshells: the 3s, 3p, and 3d orbitals. Therefore, two electrons fill the 3s orbital and six electrons fill the 3p orbitals. We would then expect electrons to fill the 3d orbitals; however, there is a filling anomaly whereby electrons fill the 4s orbital first (it is energetically favorable for the 4s orbital to be filled first). Therefore, two electrons fill the 4s orbital and seven electrons then occupythe 3d orbital: choices B and C can be eliminated and choice A is the correct response.
What is the maximum number of electrons that an orbital with a magnetic quantum number of two could hold? A. 2 B. 5 C. 8 D. 10
A. 2 The magnetic quantum number specifies the orientation of the orbital, and is limited by the values of . For this question, the value of the magnetic quantum number given in the question stem is irrelevant, as orbitals hold a maximum of two electrons at all times.
What is the ground-state electron configuration of Ga+? A. 1s22s22p63s23p64s23d104p2 B. 1s22s22p63s23p64s23d10 C. 1s22s22p63s23p64s23d104p1 D. 1s22s22p63s23p64s23d94p1
B. 1s22s22p63s23p64s23d10 In order to answer this question, first determine the electron configuration of Ga. It is [Ar]4s23d104p1. By losing one electron to form Ga+, the electron will be removed from the highest energy shell, or the 4p orbital. Thus, the electron configuration of Ga+ is [Ar]4s23d10, or choice (B).
The following unbalanced equation shows the reaction of ammonia with cupric oxide. If the coefficient in front of NH3 is one, what is the coefficient in front of Cu? NH3 + CuO --> Cu + N2 + H2O A. 3 B. 3/2 C. 1 D. 1/2
B. 3/2 Before answering the question, we must first balance the equation. Looking at the reaction given, there are two nitrogen atoms on the right, but only one on the left. Place a 2 in front of the ammonia. 2NH3 + CuO --> Cu + N2 + H2O Next, balance the hydrogen atoms by placing a 3 in front of the water molecule. 2NH3 + CuO --> Cu + N2 + 3H2O Now, balance the oxygen atoms. 2NH3 + 3CuO --> 3Cu + N2 + 3H2O If the coefficient in front of the ammonia molecule was one, we much halve the coefficients in our balanced equation. The reaction becomes: NH3 + 3/2 CuO --> 3/2 Cu + 1/2 N2 + 3/2 H2O The coefficient in front of Cu is 3/2, choice (B)
Which set of elements has valence electrons in the p shell? A. Alkali metals B. Halogens C. Transition metals D. Alkaline earth metal
B. Halogens Familiarity with the common names of the groups of the periodic table is necessary to answer this question. Choice (A), the alkali metals are the first column of the periodic table and are in the s block. The halogens, choice (B), are group VII and hence have valence electrons in the p shell. The transition metals, choice (C) are in the d block and their valence electrons are in the s and d shells. Choice (D), the alkaline earth metals, are in group II and also in the s block. Choice (B) is the only choice with valence electrons in the p shell.
Which of the following are categories for the formation of sulfur dioxide in the reaction shown below? S(s) + O2(g) --> SO2(g) I. Reduction-oxidation II. Combustion III. Single Displacement A. II only B. I and II only C. I and III only D. II and III only
B. I and II only Sulfur dioxide forms by burning sulfur in the presence of oxygen. Hence, the reaction shown is a combustion reaction, statement II. Eliminate answer choice (C). The sulfur and oxygen each have oxidation numbers of zero because they are in their elemental states. In sulfur dioxide, the oxidation number for oxygen becomes -2 and the oxidation number for sulfur becomes +4. Hence, a reduction-oxidation reaction is occurring, statement I. This eliminates choices (A) and (D). Statement III is incorrect because single displacement reactions follow the general formula, A + BC --> AB + C. The reaction shown follows the formula A + B --> AB.
Two electrons with the same n, and ms values: A. always violate the Pauli exclusion principle B. can be in different orbitals of the same subshell. C. are paired. D. must be in the same atom.
B. can be in different orbitals of the same subshell. Let's think about this question before looking at the answer choices. Consider one possibility for two electrons with the same n, and ms values. The two electrons could be in a 2p subshell, and the configuration would look like: __ __ ___ pxpy Pz Now, consider the answer choices. Electrons with these quantum numbers may not violate the Pauli exclusion principle, and so choice (A) is incorrect. The electrons can be in different orbitals of the same subshell, as they appear above, so choice (B) is okay. Choice (C), the electrons are paired, is not true, so this answer can be eliminated. Considering (D), the electrons can be in the same atom, but we can not necessarily say that they "must" be.
Which of the following shows the formation of glucose (C6H12O6) from its elements? A. 6C(g) + 6H2O(g) --> C6H12O6(s) B. 6C(g) + 6H2(g) + 3O2(g) --> C6H12O6(s) C. 6C(s, graphite) + 6H2(g) + 3O2(g) --> C6H12O6(s) D. 6C(s, graphite) + 6H2O(l) --> C6H12O6(s)
C. 6C(s, graphite) + 6H2(g) + 3O2(g) --> C6H12O6(s) In a formation reaction, all of the reactants are in their standard elemental state. Choices (A) and (D) include water as one of the reactants, which is a molecule, not an element. Choices (A) and (D) can be eliminated. In choice (B), the reacting carbon exists as a gas, which is not carbon's standard state. The standard state of carbon is solid graphite. Thus, in choice (C) all the reactants are in their standard elemental state.
When chlorofluorocarbons, such as CFCl3, diffuse into the stratosphere, ultraviolet light causes their decomposition. The decomposition products react with ozone to produce oxygen. Which of the following reactions represents the decomposition of CFCl3? A. CFCl3 + O --> CFCl2O + Cl B. CFCl3 + O3 --> CFCl2 + ClO + O2 C. CFCl3 --> CFCl2 + Cl D. CFCl3 + O2 --> CFCl2 + ClO
C. CFCl3 CFCl2 + Cl A decomposition reaction follows the general formula AB A + B. The only answer choice that corresponds to this general formula is choice (C). The information given in the question stem is extraneous, as the reaction of chlorofluorocarbons with ozone has no bearing on the decomposition of chlorofluorocarbons.
Which of the following is the correct definition of Hund's Rule? A. Electrons will fill orbitals so that an atom has the highest possible energy. B. No two electrons can possess the same four quantum numbers. C. Electrons prefer to occupy degenerate orbitals and have parallel spins. D. The greater the principal quantum number, the greater the energy of the electron shell.
C. Electrons prefer to occupy degenerate orbitals and have parallel spins. (C) Since electrons in degenerate orbitals (i.e. different orbitals that have the same energy) with parallel spins experience less repulsion than electrons in the same orbital with opposite spins, electrons would rather occupy degenerate orbitals and have parallel spins than occupy the same orbital and have opposite spins. This is known as Hund's rule, so choice C is the correct response. Choice B is a correct statement, but it is known as the Pauli exclusion principle. It states that no two electrons in any one atom can have the same set of all four quantum numbers; that is, no more than two electrons can occupy an orbital, and when two electrons do occupy the same orbital, their spins must be opposite. Choice A is an incorrect statement: electrons fill orbitals so that an atom has the lowest possible energy, not the highest possible energy (this is known as the Aufbau principle). Finally, choice D can be eliminated because although this is a true statement, it is not the correct definition of Hund's rule.
What type of force holds ions together in ionic solids? A. Hydrogen bonds B. Covalent bonds C. Electrostatic interaction D. Dipole-dipole forces
C. Electrostatic interaction (C) Ionic solids—as the name implies—consist of anions and cations that occupy different points in the crystal. Because the particles are charged, the force of attraction between them is electrostatic (electrostatic attraction is the attraction between two species with opposite charges). (You may be more familiar with the term ionic bonds but ultimately ionic bonds arise from the electrostatic attractions between positive and negative charges.) (A) is incorrect because hydrogen bonds in solids are only found in molecular crystals such as ice. (B) can be eliminated because covalent bonds are found in covalent crystals such as diamond, where electrons are shared between atoms. (D) can be eliminated because dipole-dipole interactions in solids are only found in molecular crystals such as SO2.
Milk of magnesia, with Mg(OH)2 as its active ingredient, treats acid indigestion by neutralizing excess acid in the stomach to create magnesium ions and water. Which of the following equations represents this reaction? A. Mg(OH)2(s) --> Mg2+ (aq) + 2OH- B. Mg(OH)2(s) + OH-(aq) --> Mg2+(aq) + 3OH-(aq) C. Mg(OH)2(s) + 2H+(aq) --> Mg2+(aq) + 2H2O(l) D. Mg(OH)2(s) + H+(aq) --> Mg2+(aq) + H2O(l) + OH-(aq)
C. Mg(OH)2(s) + 2H+(aq) --> Mg2+(aq) + 2H2O(l) The question stem states that Mg(OH)2 reacts with acid, which means that the Mg(OH)2 reacts with H+. Eliminate choices (A) and (B). The question stem states that the products are magnesium ions and water. The only choice that fits the given information is choice (C).
Which is higher in energy, a pz or a py orbital with the same value of n? A. pz B. py C. Neither
C. Neither The pz and py orbitals are equal in energy. The value of ml does not affect the energy of the orbital -- it only dictates the orientation. The pz, py, and px orbitals are degenerate, or equal in energy.
What type of reaction is Equation 1? Na2CO3(aq) + Ca(OH)2(aq) CaCO3(s) + 2NaOH(aq) A. Reduction-oxidation B. Decomposition C. Precipitation D. Neutralization
C. Precipitation Equation 1 follows the general formula AB + CD AC + BD, a double displacement reaction. The species in the reaction do not change oxidation state, and they do not decompose. Choices (A) and (B) can be eliminated. Two types of double displacement reactions are precipitation and neutralization. The reactants are in the aqueous phase, but solid calcium carbonate precipitates as the reaction proceeds. The reaction is a precipitation reaction, choice (C).
What is the molecular geometry of PCl3? A. Bent B. Trigonal planar C. Trigonal pyramidal D. Tetrahedral
C. Trigonal pyramidal (C) Phosphorus has five valence electrons and needs three more electrons to complete its octet. Chlorine has seven valence electrons and needs one more electron to complete its octet. Phosphorus shares a pair of electrons with each of three chlorines, so all atoms achieve a complete octet. Consequently, the central phosphorus atom is surrounded by three pairs of bonding electrons, and one pair of nonbonding electrons. These pairs of electrons repel each other and arrange themselves in such a way as to achieve maximum separation. Since there three pairs of bonding electrons and one pair of nonbonding electrons, the electron pairs orient themselves so that they point towards the corners of a tetrahedron. However, the nonbonding electron pair is not considered when describing the molecular geometry, and so the observed geometry of the molecule is trigonal pyramidal. Choice D is incorrect because a tetrahedral molecular geometry is observed when a central atom is surrounded by four pairs of bonding electrons; choice B is incorrect because a trigonal planar geometry is observed when a central atom is surrounded only by three pairs of bonding electrons and no nonbonding electrons; and choice A is incorrect because a bent geometry is observed when a central atom is surrounded by two pairs of bonding electrons and two pairs of nonbonding electrons.
Which of the following will behave most similar to LiCl? A. MgCl2 B. KCl C. NaH D. BF3
Choice (B), KCl will behave most similarly to LiCl because both K and Li are in the same group. In choice (A), magnesium, Mg, is group II and is not expected to behave as lithium does. In choice (C), while Na is in the same group as Li, H is not in the same group as Cl. In choice (D) B is group III and is not expected to behave as lithium does. Recognizing that elements in the same group exhibit similar behavior is a necessary skill for Test Day.
Which of the following electron configurations violates the Aufbau principle? A. 1s22s22px22py1 B. 1s22s22px12py12pz1 C. 1s22s22px32py22pz2 D. 1s22px12py12pz1
D. 1s22px12py12pz1 The Aufbau principle states that electrons fill in the lowest energy orbital first. Therefore we are looking for the answer choice that fills electrons in the orbitals in the wrong order. In (A), the configuration is filling in the proper order, except that the third electron in the 2p orbital is placed in the px orbital before being placed in the pz orbital. This is a violation of Hund's rule. In choice (B), the electron configuration is fine as written. In choice (C) there are seven electrons in the p orbital, which is not possible according to quantum theory. In choice (D), electrons are placed in the 2p orbital before they are placed in the 2s orbital. The 2s orbital is lower in energy than the 2p orbital, so electrons should have been placed in it first according to the Aufbau principle. Thus, choice (D) violates the Aufbau principle.
How would one classify the following reaction? 2NaCl(s) 2Na(s) + Cl2(g) A. Formation B. Double displacement C. Corrosion D. Decomposition
D. Decomposition The reaction is of the general formula AB A + B, or a decomposition reaction.
Which of the following is not a classification for the creation of carbon dioxide in the reaction shown below? C(g) + 02(g) --> C02(g) A. Combustion B. Combination C. Reduction-oxidation D. Formation
D. Formation In the reaction shown, the carbon is burning in oxygen to create carbon dioxide, hence a combustion reaction. The reaction also shows carbon and oxygen combining to form carbon dioxide, hence a combination reaction. The oxidation state of both carbon and oxygen change during the course of the reaction, thus it is also a reduction-oxidation reaction. The carbon and oxygen gas each have oxidation numbers of zero. In carbon dioxide, the oxidation number for oxygen becomes —2 and the oxidation number for carbon becomes +4. In a formation reaction, all reactants must be in their standard state. In the reaction, carbon is a gas and the standard state of carbon is solid graphite.
Why does H2O have a higher boiling point than H2Se or H2Te? A. H2O molecules undergo dispersion forces. B. H2O molecules can pack together more closely. C. H2O molecules undergo dipole-dipole interaction. D. H2O molecules undergo hydrogen bonding.
D. H2O molecules undergo hydrogen bonding. (D) Hydrogen bonds are a type of intermolecular force, but unlike dipole-dipole interactions and dispersion forces, they are very strong. In order for hydrogen bonding to occur, a molecule must possess a hydrogen attached to a highly electronegative element, specifically nitrogen, oxygen, or fluorine; this hydrogen can then interact with the electronegative element of another molecule. Molecules that undergo hydrogen bonding are usually quite difficult to break apart; therefore, they possess unusually high boiling points. Water molecules contain two hydrogens attached to an electronegative oxygen; as a result, water can undergo hydrogen bonding, and it has an unusually high boiling point. On the other hand, H2Se and H2Te contain hydrogens that are not attached to electronegative elements, so they cannot undergo hydrogen bonding, and they possess boiling points that are significantly lower than water. Dipole-dipole interactions are forces that act between molecules that possess dipole moments. Although water is a polar molecule, dipole-dipole interactions are relatively weak compared to hydrogen bonding and are therefore not sufficient when accounting for the unusually high boiling point of water (choice C can be eliminated). Dispersion forces occur when the electron clouds of nonpolar molecules instantaneously polarize (and instantaneously polarize each other), resulting in a temporary induced dipole moment and a weak attraction. This is a very small effect that is of importance only when no other types of interactions are possible, for example in a sample of argon atoms. Choice B is incorrect because the ability of compounds to pack together affects the melting point of a compound, not the boiling point.
Nitric oxide (NO) participates in the breakdown of ozone by the following reaction mechanism: NO + O3 NO2 + O2 NO2 + O NO + O2 The overall reaction is: O3 + O 2O2 What is the role of NO2 in the overall reaction? A. Catalyst B. Product C. Reactant D. Intermediate
D. Intermediate The NO2 is created during the course of the overall reaction, but then it is consumed by reacting with O. Thus, NO2 is an intermediate in the overall reaction. The reactants are O3 and O; the product is O2. NO behaves as a catalyst.
Iron, cobalt and nickel display the property of ferromagnetism, or the ability to become permanently magnetized after being exposed to a magnetic field. After being exposed to magnetization, the unpaired d electrons of these elements align in a parallel manner, resulting in a strong magnetic moment. Would zinc be expected to display ferromagnetism? A. Yes, because zinc is a transition metal along with iron, cobalt, and nickel and would be expected to have similar properties. B. Yes, because zinc has unpaired d electrons. C. No, because only elements in the same column of the periodic table have properties in common. D. No, because zinc is diamagnetic.
D. No, because zinc is diamagnetic. As stated in the question stem, unpaired d electrons are necessary for ferromagnetism to occur. The difference between zinc and iron and cobalt and nickel is that all of the electrons of zinc are paired, or zinc is a diamagnetic species, whereas iron, cobalt and nickel have unpaired electrons. Therefore choice (D) is correct. Choice (A) is wrong because while all of the metals are transition metals, zinc varies from the other three metals because it lacks unpaired electrons. Choice (B) is wrong because zinc only has paired d electrons. Choice (C) is wrong because, while elements in the same group have similar properties, elements in the same row of the periodic table can have similar properties as well. This is pointed out in the question stem, as iron, cobalt and nickel are not in the same group, yet they share a common property.
Is the following statement true or false? The electron configuration of lithium is 1s^3.
False The third electron is put in the 2s orbital, so the electron configuration of lithium is 1s^2 2s^1.
Is the following statement true or false? Phosphorous is isoelectronic with nitrogen.
False. Phosphorous and nitrogen are both in their elemental states, so they cannot be isoelectronic with respect to each other. Furthermore, phosphorous has an atomic number of 15 while nitrogen's atomic number is 7.
The magnetic quantum number divides the subshells into individual orbitals and defines the orientation of the orbitals.
For an electron with =1, or in a p orbital, has three different values: -1, 0, and +1. These three values represent the individual orbitals of the subshell. The orbitals are designated px, py, and pz to specify their orientation. A maximum of two electrons can occupy each pz, py, or px orbital. Therefore, a maximum of six electrons can occupy the subshell.
Value of l
For any given n, the value of "l" can be any integer from 0 to (n- 1). 0-->s 1-->p 2-->d 3-->f
Losing Electrons...
Is like losing a bad habit. You become more positive
Which of the following statements about atomic radius is true? A. It increases from left to right across a period and decreases down a group. B. It decreases from left to right across a period and increases down a group. C. It increases from left to right across a period and increases down a group. D. It decreases from left to right across a period and decreases down a group.
It decreases from left to right across a period and increases down a group. (B) From left to right across a period, the atomic number, and therefore the number of electrons, increases. In any given period, the principal quantum number of each element remains the same, so electrons fill the same shell. However, because atomic number increases from left to right across a period, the number of protons, and therefore the nuclear charge, increases. Since the nuclear charge increases from left to right across a period but the electrons fill the same shell, the electrons feel an increasing pull toward the nucleus, and the atomic radius decreases from left to right across the periodic table (choices A and C can be eliminated). Moving down a group, the principal quantum number increases, so the valence electrons are farther away from the nucleus. As a result, the ability of the nucleus to pull electrons towards itself decreases down the group and the atomic radius increases; therefore, choice D can be eliminated, and choice B is the correct response.
First figure out the electron configuration of titanium.
Looking at the periodic table, we notice that titanium has Z = 22, and it is found in the fourth period and second group of the transition metals. The electronic configuration of titanium is [Ar] 4s^2 3d^2. As you can see, there are unpaired electrons in this species, so titanium is paramagnetic.
REACTIONS AND MECHANISMS QUIZ ↓
REACTIONS AND MECHANISMS QUIZ ↓
Structure and Bonding (See Print)
Structure and Bonding (See Print)
Aufbau principle
The Aufbau principle or building-up principle, which governs electron configurations, states that electrons fill in the lowest energy orbital first.
What is the electron configuration of Ge? A. [Ar]4s^2 3d^10 4py^2 B. [Ar]4s^2 3d^10 4px^1 4py^1 4pz^1 C. [Ar]4s^2 3d^10 4py^1 D. [Ar]4s^2 3d^10 4px^1 4py^1
[Ar]4s^2 3d^10 4px^1 4py^1 The electron configuration of Ge is [Ar]4s23d1042. This eliminates choices (B) and (C) because they do not have the correct number of electrons in the 4p subshell. According to Hund's rule, the second electron in the -orbital should go in the y or z orbital if there is already an electron in the x orbital. Choice (A), then, violates Hund's rule. This leaves choice (D) as the correct answer.
