Mahase Ch 7.1-7.5 and Visible Spectrometry Concepts

How do you arrange ions/atoms in order or size?

**Include: First check if any two or more ions or atoms are isoelectronic; if so, gauge those from their #protons, and the rest (the non isoelectronic ones) based on their charges (cations left to right decrease-smaller than parent atoms-and anions left to right increase-larger than parent atoms, and ionic radii increase down a group)

What are Two Examples Involving Ordering Size of Ionic Radii?

1. Ex: Arrange Mg2+, Ca2+, and Ca in order of decreasing radius 2. Solution: Cations are smaller than their parent atoms, and so Ca2+<Ca; Ca is below Mg in group 2A, Ca2+ is larger than Mg2+: Ca>Ca2+>Mg2+ 3. Ex: Which ion is largest: S2-, S, or O? Answer: S2- anions > larger than their parent atoms

What is electronegativity?

1. A measure of the ability of an atom that is bonded to another atom to attract electrons to itself; 2. the affinity that an atom has for an electron when bonded covalently to another atom 3. The greater an atom's electronegativity, the greater its ability to attract electrons to itself

What is an Isoelectronic Series?

1. A series of atoms, ions, or molecules having the same number of electrons 2. (ex: each ion in isoelectronic series O2-, F-, Na+, Mg2+, A3+ has 10 electrons); 3. In any isoelectronic series, we can list members in order of increasing atomic #; 5. Because # e- remains constant, in an isoelectronic series, ionic or atomic radius decreases w/ increasing nuclear charge (#protons/atomic#) as the electrons are more strongly attracted to the nucleus:

How do you Define the Size of an Atom?

1. According to quantum mechanical model of the atom, atoms do not have sharply defined boundaries at which electron distribution becomes zero; 2. However, atomic size can be defined in several ways; 3. based on distances between atoms in various situations

What are the Trends in Reactivity for Metals Across a Period?

1. As metals lose electrons to form cations; 2. reactivity decreases as you go across a period from left to right 3. Explanation: Metals react by losing electrons; when ENC is greater (more positive), electrons are held closer to the nucleus, preventing loss of electrons and thus the atom is less reactive

What is the Trend in Reactivity for Nonmetals Across a Period?

1. As nonmetals gain electrons to form anions; 2. reactivity increases as you go left to right in a period; 3. (fluorine is the most reactive nonmetal)

Who were Dmitri Mendeleev and Lothar Meyer?

1. Both scientists noted that similar chemical and physical properties recur periodically when elements are arranged in order of increasing atomic weight; 2. Both independently came to the same conclusion about how elements should be grouped; 3. scientists at the time had no knowledge of atomic numbers, 4. but as atomic weights generally increase with atomic number, 5. so both scientists arranged elements in proper sequence

How was the periodic table developed?

1. Certain Elements (such as gold-Au) appear in nature in elemental form and were thus discovered thousands of years ago; 2. However, some elements (such as Tc) are radioactive and unstable, 3. and we know about them only because of technology developed during the 20th century; 4. As such, the majority of elements readily form compounds

What are oxides (basic, amphoteric, acidic)?

1. Compounds that contain oxygen that is combined with one other element (ex: Na2O, MgO, etc.) a. Basic Oxide: PH>7: in water they form OH- (hydroxide ions), which are responsible for their properties (ex: Na2O, MgO, CaO, CuO etc.) b. Amphoteric Oxide: Has both basic and acidic properties; can react with both acids and bases (ex: Al2O3, SiO2) c. Acidic Oxide: PH<7: In water they form H+ (hydrogen ions/protons), which are responsible for their properties (ex: P4O6, SO2,P4O10, SO3, etc.)

What is an Example of Periodic Trend in Valence Electron Zeff Values Across a Period?

1. Core electrons of Li (1s22s1)-# 3-screen 2s valence electron from the 3+ nucleus efficiently; valence electron experiences ENC of roughly: 3 -2 = 1+ 2. For Be (1s22s2)-# 4-the ENC experienced by each valence electron is larger because in this case, the two 1s electrons screen a 4+ nucleus, and ENC experienced by each 2s electron is roughly: 4 - 2 = 2+

What is the screening constant?

1. Denoted by "S"; represents portion of nuclear charge that is screened from a valence electron by other electrons in the atom 2. Because core electrons are most effective at screening a valence electron from the nucleus, the value of "S" is close to the # core electrons in an atom; 3. electrons in the same valence shell do not screen each other very effectively, but they do affect value of "s" slightly

What is an Example of Group 1A to 2A Discontinuity in Electron Affinity?

1. E- affinities of Be and Mg are positive; 2. because the added electron would reside in a previously empty "p" subshell that is higher in energy (2A to 3A)

What is the periodic trend of Electron Affinity Down a Group?

1. Electron affinities do not change greatly in moving down a group; 2.there are many inconsistencies, and as such, it is not worth establishing a general trend; 3. Ex: In proceeding from F to I, avg. distance between the added e- and the nucleus steadily increases, 4. causing electron-nucleus attraction to decrease

What is the Difference Between Electronegativity and Electron Affinity?

1. Electronegativity is defined as the ability of an atom in a molecule to attract electrons to itself, 2. while electron affinity measures the ease with which an isolated atom gains an electron

What is the Fourth Rule for the Electron Configuration of Ions?

1. Electrons added to an atom to form an anion are added to the empty or partially filled orbital having the lowest value of "n" 2. (ex: an electron added to an F atom to form the F- ion goes into the one remaining vacancy in the 2- subshell):

What is John Slater's Method of Calculating ENC?

1. Electrons for which "n" is larger than value of "n" for electron of interest contribute 0.00 to the value of "S" 2. Electrons with same value of "n" (same shell) as electron of interest contribute 0.35 to value of "s" 3. Electrons for which "n" is one less than "n" for electron of interest contribute 0.85 (those with even smaller values of "n" contribute 1.00)

What are valence orbitals?

1. Elements in the same column of the periodic table contain the same number of electrons in their valence orbitals; 2. (the occupied orbitals that hold the electrons involved in bonding) 3. Ex: O ([He]2s22p4) and S ([Ne]3s23p4) are both in group 6A 4. Elements in the same groups of the periodic table generally have similar chemical properties; 5. however, physical properties are not necessarily similar

Who was Henrey Moseley?

1. English physicist who developed the concept of atomic numbers by bombarding different elements with high-energy electrons; 2. He found that each element produced x-rays of a unique frequencies that generally increased as atomic mass increased 3. Henry Moseley arranged x-ray frequencies in order by assigning a whole number (atomic number) to each element, 4. which he correctly identified as the number of protons in the nucleus of an atom

What are the Successive Values of Ionization Energies for the Elements Sodium Through Argon (kJ/mol)?

1. Every element exhibits large increase in IE when one of its inner electrons is removed; 2. this supports the idea that only outermost electrons are involved in sharing and transfer of e- that give rise to chemical bonding and reactions; 3. Inner e- are too tightly bound to nucleus to be lost from atom or even shared with another atom:

What are the General Trends in Bonding Atomic Radii for Periods 1 Through 5?

1. We mean the bonding atomic radius when we speak of the "size" of the atom 2. (for helium and neon, bonding atomic radius must be estimated because there are no known compounds of these elements):

What is an Example Involving Ordering the Size of Atoms?

1. Ex: Arrange the atoms P, S, As, and Se in order of increasing size 2. Solution: P and S are in same period, with A to right of P (therefore, radius of S is smaller than that of P), as As is directly below P 3. (in assessing size, go across period first and then down or up to a different group-addition of a shell trumps increasing size across a period), and Se is directly below S: S<P<Se<As

What are Two Examples Involving Arranging Ionic Radii in Terms of Size in an Isoelectronic Series?

1. Ex: Arrange the ions K+, Cl-, Ca2+, and S2- in order of decreasing size: 2. Solution: In such a series, size decreases as nuclear charge increases; atomic #s of the ions are S-16, Cl-17, K-19, Ca-20; thus, the ions decrease in size in the order: S2- > Cl- > K+ > Ca2+ 3. Ex: In isoelectronic series Rb+, Sr2+, Y3+, which ion is the largest? Answer: in such a series, size increases as nuclear charge decreases, so Rb+ is largest, as atomic # of Sr-38, Y-39, Rb-37

What is an Example Involving Finding Trends in Ionization Energy?

1. Ex: Between the elements Li, Ca, and S in the periodic table, which one has the largest second ionization energy?: 2. Solution: As Na has one valence e-, I2 of this element is associated with the removal of a core e-, whereas S and Ca have two or more valence e-; thus Na should have largest I2

What is an Example Involving Periodic Trends in Ionization Energy?

1. Ex: Referring to a periodic table, arrange the atoms: Ne, Na, P, Ar, K, in order of increasing first IE 2. Solution: Because Na, P, and Ar are in the same period, I1 will vary in the order: Na<P<Ar; because Ne is above Ar in group 8A, Ar<Ne; similarly, K is directly below Na in group 1A and so K<Na: K<Na<P<Ar<Ne

What is an Example Involving Calculating Bond Lengths in a Molecule?

1. Ex: Use the above figure to predict the lengths of the C-S, C-H, and S-H bonds in CH3SH 2. Solution: C-S bond length = bonding atomic radius of C + bonding atomic radius of S = 0.77 Å + 1.02 Å = 1.79 Å; C-H bond length = 0.77 Å + 0.37 Å = 1.14 Å, S-H bond length = 1.02 Å + 0.37 Å = 1.39 Å

What are Two Examples Involving Writing Electron Configurations of Ions?

1. Ex: Write the electron configuration for a. Ca2+ b. Co3+, and c. S2- 2. Solution: a. Ca2+: [Ar] b. Co3+: [Ar]3d6 c. S2-: [Ne]3s23p6 = [Ar] 3. Ex 2: Write the electron configuration for a. Ga3+ b. Cr3+ c. Br- Solution: a. Ga3+: [Ar]3d10 b. Cr3+: [Ar]3d3 c. Br-: [Ar]3d104s24p6 = [Kr]

What is the First Discontinuity in Periodic Trend in Electron Affinity (Groups 1A and 2A)?

1. First discontinuity occurs between groups 1A and 2A; 2. the added e- must go in a p-orbital not an s-orbital; 3. and the e- is farther from nucleus, feeling repulsions from the s-electrons 4. Since elements in 2A contain two valence e-, have a filled "s" orbital and thus don't want an additional electron

What is the Trend Across Each Period of the Periodic Table for Successive Values of IE?

1. For I2, element in Group 1A as largest in a given period (one valence e-: corresponds to removal of first core), 2. for I3 in a given period, element in group 2A has largest (two valence e-: corresponds to removal of first core), 3. for I4, element in group 3A has largest in a given period (three valence e-: corresponds to removal of first core), etc.

What are the Periodic Trends in Size of Ions Across a Period?

1. For cations, ionic radius decreases from left to right across any period of the periodic table (smaller than parent atoms) 2. (From Group 1A-charge: 1+-to Group 3A-charge: 3+ and 4A-4+) due to increasingly reduced # electron-electron repulsions 3.(Resulting from increasing removal of electrons) 4. From Group 4A to 5A, increases, but For anions, ionic radius decreases from left to right across a period (from Group 5A-charge: 3- to Group 7A-charge: 1-) because reduced electron-electron repulsions

What are the Periodic Trends in Size of Ions Down a Group?

1. For ions carrying the same charge, ionic radius increases in moving down a group in the periodic table; 2. as the principal quantum number "n" of the outermost occupied shell/orbital of an ion increases, radius of the ion increases (increasing # shells)

What is the Relationship Between Effective Nuclear Charge and Radial Probability Function?

1. For many-electron atom, energies of orbitals with same "n" value increase with increasing "l" value 2. (ex: in C atom-1s22s22p2-energy of 2p orbital (l =1) is higher than that of the 2s orbital (l =0) even though both orbitals are in the n=2 shell 3. Difference in energies due to radial probability functions for orbitals; 4. greater attraction between 2s electron and nucleus leads to lower energy than for the 2p orbital:

What is the Trend in Reactivity for Nonmetals Down a Group?

1. For nonmetals, reactivity increases as you go up a group; decreases as you go down a group 2. Explanation: as nonmetals gain electrons to form anions, when distance of electron is closer to the nucleus, it facilitates the gain of the electron

How do you calculate Bonding Atomic Radius from Bond Lengths?

1. From observations of the internuclear distances in many molecules, each element can be assigned a bonding atomic radius: 2. Ex: in I2 molecule, internuclear distance is 2.66 Å, so bonding atomic radius is 2.66/2 = 1.33 Å

What is the Periodic Trend in Valence-Electron Zeff Values Down a Group?

1. Going down a column, the ENC experienced by valence electrons changes far less than it does across a period; 2. While we would expect that the ENC experienced by elements in a particular group to be the same, the ENC increases slightly down a column because: 3. Explanation: the more diffuse (more spread out) core electron cloud is less able to screen valence electrons from the nuclear charge; 4. (as you go down a period, you add a shell)

What is the Nonbonding Atomic Radius/Van Der Waals Radius?

1. Half the distance between two nonbonded adjacent atoms 2. (ex: for a collection of argon atoms in the gas phase-or any noble gas atom-when two of these atoms collide with each other, they ricochet apart because they cannot form a bond; 3. as such, the shortest distance separating the two nuclei during such collisions is twice the radii of the atoms)

What are the General Periodic Trends in First Ionization Energy?

1. I1 generally increases moving across period from left to right; 2. alkali metals show lowest first IE in each period, and noble gases show highest 3. (slight discontinuities: from group 2A to 3A, there is decrease, and same from group 5A to 6A) 4. I1 generally decreases in moving down any column in the periodic table (Ex: first IE of noble gases follow order: He>Ne>Ar>Kr>Xe):

What is the Second Rule for the Electron Configuration of Ions?

1. If an addition e- is removed past the valence shell (ex: forming Fe3+), it comes from a 3d orbital because all the orbitals with n=4 are empty: Fe2+([Ar]3d6)→Fe2+([Ar]3d5) + e-

What is the Net Electric Field Created by the Nucleus?

1. In a many-electron atom, each electron is simultaneously attracted to the nucleus and repelled by other electrons; 2. we treat the electron as though it were moving in the net electric field created by the nucleus and the electron density of other electrons; 3. We view this net electric field as if it results from a single positive charge located at the nucleus, called the effective nuclear charge (Zeff)

Why can effective nuclear charge not be calculated exactly?

1. In a sodium atom (as in all other atoms), the ENC situation is more complicated; 2. because the 3s electron has a small probability of being closer to the nucleus, in the region occupied by the core electrons; 2. Thus, there is a probability that this electron experiences a greater attraction than the simple S = 10 model suggests; 3. this greater attraction increases the value of Zeff for the 3s electron in Na from the expected: Zeff = 1+ to Zeff = 2.5+; 4. the fact that the 3s electron spends some small amount of time close to the nucleus changes the value of "S" from 10 to 8.5

What is the Relationship Between ENC and Ionization Energy?

1. In general, smaller atoms have higher ionization energies; 2. the same factors that influence atomic size also influence ionization energies; 3. The energy needed to remove an e- from the outermost occupied shell depends on both the ENC; 4. or the decreasing distance from the nucleus increases the attraction between the e- and the nucleus

What was the Basis for Developing the Concept of Effective Nuclear Charge?

1. In general, there are so many electron-electron repulsions that we cannot analyze the situation exactly, 2. but we can estimate the attractive force between any on electron and the nucleus; 3. by considering how the electron interacts with the average environment created by the nucleus and the other electrons in the atom

How was the calculation of bonding atomic radius developed?

1. In molecules, an attractive interaction exists between any two adjacent atoms in the molecule, leading to a chemical bond between the atoms 2. (the attractive interaction brings the two atoms closer together than they would be in a nonbonding collision) 3. We can define an atomic radius based on distance separating the nuclei (internuclear distance) when two atoms are bonded together

What is the Periodic Trend in First Ionization Energy Across a Period?

1. In moving across a period from left to right, there is both an increase in ENC and a decrease in atomic radius; 2. causing the ionization energy to increase; 3. As attraction increases, it becomes more difficult to remove the e-, thus, the ionization energy increases

What is the Periodic Trend in First Ionization Energy Down a Group?

1. In moving down a group, atomic radius increases while ENC increases gradually; 2. thus the attraction between nucleus and the e- decreases, causing the ionization energy to decrease 3. In going down a column, less energy is required to remove the first e-; 4. for atoms in same group, Zeff is essentially the same, but valence electrons are farther from the nucleus

What are Variations in Successive Ionization Energies (i.e. I1, I2, etc.)?

1. Ionization energies increase for a given element as successive ions are removed: I1<I2<I3, etc.; 2. This trend exists because with each successive removal, an electron is being pulled away from an increasingly more positive ion, requiring increasingly more energy 3. There is a sharp increase in IE that occurs when an inner-shell electron is removed

What is the Difference Between Ionization Energy and Electron Affinity?

1. Ionization energy measures the ease with which an atom loses an e-, while electron affinity measures the ease with which an atom gains an e-; 2. The greater attraction between an atom and an added e-, the more negative the atom's electron affinity; 3. thus, in general, e- affinity becomes more exothermic in moving from left to right across a row of periodic table

How do you define the size of an ion?

1. Just as bonding atomic radii can be determined from interatomic distances in molecules, 2. ionic radii can be determined from interatomic distances in ionic compounds; 3. Similarly to the size of an atom, the size of an ion depends on its nuclear charge, the # electrons it possesses, and the orbitals in which the valence electrons reside

How do you Estimate Bond Lengths From Bonding Atomic Radii?

1. Knowing the atomic radii allows us to estimate bond lengths in molecules 3. in CCl4 the measured length of the C-Cl bond is 1.77 Å, very close to the sum-0.77 Å + 0.99 Å-of the bonding atomic radii of C and Cl)

What are the Factors that Affect the Electron's Force of Attraction to the Nucleus?

1. Many properties of atoms depend on electron configuration and how strongly the outer electrons in the atoms are attracted to the nucleus; 2. The force of attraction increases as the nuclear charge increases, and 3. decreases as the electron moves farther from the nucleus;

What were the Discoveries of Dmitri Mendeleev?

1. Mendeleev's insistence that elements with similar characteristics be listed in the same column forced him to leave blank spaces in the periodic table 2. Ex: Gallium (Ga) and Germanium (Ge) were unknown to Mendeleev, referring to Ga as "eka-aluminum" (under Al) and Ge as "eka-silicon (under silicon); 3. after the elements under which they appeared in his table

What is electron affinity?

1. Most atoms can also gain electrons to form anions; 2. the energy change that accompanies the addition of an electron to a gaseous atom or ion 3. It measures the attraction, or affinity of the atom for the added electron; 4. For most atoms, energy is released when an e- is added;

What are the Trend In Reactivity for Metals Down a Group?

1. Reactivity in the metals increases as you go down a group; 2. with the addition of shells, the increasing distance between the electron and the nucleus facilitates the loss of electrons

What is the Second Discontinuity in Periodic Trend in Electron Affinity (Groups 4A and 5A)?

1. Second discontinuity occurs between groups 4A and 5A; 2. group 5A has no empty orbitals (Hund's rule→3p^3); 3. because group 5A elements have half-filled "p" subshells, the added e- must be put in an orbital that is already occupied, resulting in larger e--e- repulsions; 4. Consequently, these elements have e- affinities that are either positive (as in N) or less negative/exothermic (P, As, Sb) than the electron affinities of their neighbors to the left

What is an Example of Variations in Successive Ionization Energies for a Given Atom?

1. Silicon (1s22s22p63s23p2); the ionization energies increase steadily from 786 kJ/mol to 4356 kJ/mol for the four e- in the 3s and 3p subshells; 2. however, removal of the 5th e- (which comes from the 2p subshell, requires a great deal more energy: 16,091 kJ/mol 3. Large increase occurs because 2p e- is not found in valence shell (core electron; 4. close to the nucleus), and therefore, it experiences a much greater ENC than do the 3s and 3p e-

What is a calibration curve?

1. So, we use something called a calibration curve 2. Absorbance values are plotted on the y axis and corresponding molar concentrations of the absorbing substance in the standard solutions are plotted on the x axis. 3. By finding the wavelength where maximum absorbance occurs, the absorbance value for each standard solution is determined. 4. By using the y = mx+b formula of a trendline fitting the calibration curve, x is determined to find the the accurate molarity of a solution.

What is an Example of Calculating Effective Nuclear Charge in the Sodium Atom?

1. Sodium has electron configuration [Ne]3s1, and its nuclear charge is Z = 11+ (has 11 protons)-there are 10 core electrons: 1s22s22p6; 2. therefore, we expect "S" to equal 10 and the 3s1 electron to experience an ENC of Zeff = 11 - 10 = 1+: 3. The ENC experienced by the valence electron in a sodium atoms depends mostly on the 11+ charge of the nucleus and the 10- charge of the core electrons

What is the Relationship Between ENC of Outer Electrons and Inner Electrons of an Atom?

1. The ENC felt by outermost electrons is smaller than that felt by inner electrons because of screening by the inner electrons; 2. The ENC felt by outermost electrons does not increase as steeply with increasing atomic # as that of inner electrons; 3. because the valence electrons only make a small contribution to the screening constant "S" 4. (core e- are more effective than valence e- at screening nuclear charge)

What is an example of an electron affinity process?

1. The addition of an e- to a chlorine atom is accompanied by an energy change of -349 kJ/mol 2. (the negative sign indicating that energy is released during the process); 3. therefore, the electron affinity of Cl is -349 kJ/mol:

How was the concept of atomic numbers developed?

1. The concept of atomic number clarified some anomalies in the periodic table of Moseley's day (which was based on atomic weights) 2. Ex: Atomic weight of Ar (# 18) is greater than that of K (#19), but chemical and physical properties of Ar are more like those of Ne and Kr (group 8A) than those of Na and Rb (group 1A)

What is an Example of Group 5A to 6A Anomaly in First IE?

1. The decrease in first IE from N ([He]2s22p3) to O ([He]2s22p4); 2. is because of the repulsion of paired e- in the p4 configuration, so that it is easier to remove an e- from the p4 configuration:

What is an Example of Group 2A to 3A Anomaly in First IE?

1. The decrease in ionization energy from Be ([He]2s2 to B ([He]2s22p1); 2. occurs because third valence e- of B must occupy the 2p subshell, 3. which is empty for Be-the 2p subshell is at a higher energy than the 2s subshell:

What is the Equation for Determining Effective Nuclear Charge?

1. The effective nuclear charge acting on an electron in an atom is smaller than the actual nuclear charge, 2. because ENC includes effect of other electrons in the atom: Zeff > Z 3. Inner electrons partially screen outer electrons from the attraction of the nucleus; 4. relationship between Zeff and # protons in nucleus (Z): Zeff = Z - S, where "S" is a positive # called the "screening constant"

What is the Periodic Trend in Valence-Electron Zeff Values Across A Period?

1. The effective nuclear charge increases from left to right across any period of the periodic table; 2. Explanation: Although # core electrons stays the same across the period (same # shells), the number of protons increases (Z), 3. and valence electrons added to counterbalance the increasing nuclear charge screen one another ineffectively

What is the Relationship Between Ionization Energy, Electron Affinity, and Electronegativity?

1. The electronegativity of an atom in a molecule is related to the atom's ionization energy and electron affinity, which are properties of isolated atoms; 2. An atom with a very negative electron affinity and a high ionization energy; 3. both attracts electrons from other atoms and resists having its electrons attracted away (highly electronegative)

What is First Ionization Energy (I1)?

1. The energy needed to remove the first electron from a neutral atom 2. (ex: the first ionization energy for the sodium atom is the energy needed to remove the first electron from a neutral atom 3. ex: the first ionization energy for the sodium atom is the energy required for the process: Na(g)→Na+(g) + e-; 4. Generic equation: M→M+ + e-

What is Second Ionization Energy (I2)?

1. The energy needed to remove the second electron, and so forth, for successive removals of additional electrons (i.e. I2, I3, I4, etc.); 2. there are as many ionization energies as electrons in a given atom 2. Ex: I2 for the Na atom is the energy associated with the process: Na+(g)→Na2+(g) + e-

What is Ionization Energy?

1. The energy required to remove an electron from a gaseous atom when the atom is in its ground state 2. (minimum energy required to remove an e- from the ground state of the isolated gaseous atom or ion) 3. The ease with which electrons can be removed from an atom or ion has a major impact on chemical behavior; 4. the greater the ionization energy, the more difficult it is to remove an electron

What is Electron Affinity in kJ/mol for Selected s-and p- Block Elements?

1. The halogens (one e- shy of a filled "p" orbital) have the most negative electron affinities); 2.by gaining an e-, a halogen atom forms a stable anion that has a noble-gas configuration

What is Effective Nuclear Charge?

1. The net positive charge experienced by an electron in a many-electron atom; 2. this charge is not the full nuclear charge because there is some shielding of the nucleus by other electrons in the atom

What is nuclear charge?

1. The number of protons in the atom; 2. some of the effectiveness of these protons is nullified by the electrons in the atom, giving rise to effective nuclear charge 3. In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons; 4. the nuclear charge that electrons experiences depends on both factors

What is the Relationship Between Size of Cation and Parent Atom?

1. When a cation is formed from a neutral atom, 2. the outermost electron is removed and # repulsions between electrons (electron-electron repulsions) are reduced, contracting the ion; 3. Therefore, cations are smaller than their parent atoms

What is visible spectrometry?

1. The process in which the amount that a chemical substance absorbs light is measured; 2.by measuring the intensity of light as a beam of light passes through a given solution 3. Measure spectrophotometry with a spectrophotometer; 4. or an apparatus that measures the amount of photons, or the intensity of light, absorbed after the spectrophotometer passes through a sample solution

What is the Bonding Atomic Radius/Covalent Radius?

1. The radius of an atom as defined by the distances separating it from other atoms to which it is chemically bonded; 2. the bonding atomic radius for any atom in a molecule is equal to half the internuclear distance (nucleus-to nucleus distance): 3. Bonding atomic radius (also known as "covalent radius") is shorter than the nonbonding atomic radius in a given atomic

What is the First Ionization Energy of Transition Metals?

1. The s- and p- block elements show a larger range of I1 values than do the transition metal elements; 2. generally, the first IEs of the transition metals increase slowly from left to right in a period; 3. the f-block metals also show only a small variation in the values of I1

What is the Periodic Trend of Electron Affinity Across A Period?

1. The trends are not as evident as they are for ionization energy; 2.however, in general, e- affinity becomes more exothermic (increases) in moving from left to right across a given period 3. (there are discontinuities Between Groups 1A and 2A and between groups 4A and 5A)

What is the First Discontinuity/Irregularity in Periodic Trend of Ionization Energy (Groups 2A & 3A)?

1. There is an irregularity in the transition from group 2A to 3A across any period, as there is a decrease in ionization energy from 2A to 3A 2. Explanation: in this case the e- is removed from a p-orbital rather than an s-orbital; 3. the e- removed is farther from the nucleus; 4. and there is also a small amount of repulsion by the "s" electrons

What is the Second Discontinuity/Irregularity in Periodic Trend of Ionization Energy (Groups 5A and 6A)?

1. There is an irregularity in the transition from group 5A to 6A across any period, as there is a decrease in first IE from 5A to 6A; 2. Explanation: it is easier to remove an e- from the p4 configuration; 3. according to Hund's rule, each electron in the p3 configuration resides in a different "p" orbital, minimizes electron-electron repulsion among the three 2p electrons 4. (half-filled p3 is more stable):

What is the Periodic Trend in Electronegativity Across a Period?

1. There is generally an increase in electronegativity across a period from left to right 2. (from most metallic elements to most nonmetallic elements); 3. Explanation: As ENC and ionization energy increases from left to right across a period; 4. the force of attraction between the electron and the nucleus increases, thus increasing affinity for electrons

What is coulomb's law?

1. This law tells us that the strength of the interaction between two electrical charges depends on the magnitudes of the charges and the distance between them; 2. As such, attractive force between electron and the nucleus (where protons reside) depends on the magnitude of nuclear charge and on the average distance between the nucleus and the electron

What is Beer's Law?

1. Utilizes the concept that the absorbance of a solution increases as the molar concentration of a light-absorbing substance increases. 2. States that a substance with a fixed concentration and path length will demonstrate a change in absorbance as wavelength changes because the value of the absorptivity depends on the wavelength of light 3. A = abc, where a is the absorptivity, b is the path length, and c is the concentration (4). 4. By using Beer's law, the concentration of an absorbing substance in a solution can be determined. 5. But, this method can cause error: 6. It relies on the standard solution being prepared without any error. The absorbing substance that deviates does not follow Beer's Law at all concentrations.

What is the Relationship Between Size of Anion and Parent Atom?

1. When electrons are added to an atom to form an anion, 2. the increased electron-electron repulsions cause the electrons to spread out more in space; 3. Therefore, anions are larger than their parent atoms

What is the First Rule for the Electron Configuration of Ions?

1. When electrons are removed from an atom to form a cation, they are always removed first from the occupied orbitals with the largest principal quantum number "n" 2. Ex: When one e- is removed from an Li atom (1s22s1)→Li+ (1s2) + e-, or when two e- are removed from Fe ([Ar]3d64s2), the 4s2 e- are the ones removed: Fe2+([Ar]3d64s2)→Fe2+([Ar]3d6) + 2e-

What is the Comparison of the Properties of Eka-Silicon Predicted by Mendeleev With the Observed Properties of Germanium?

1. When the elements Ge and Ga were discovered, 2. their properties closely matched those predicted by Mendeleev:

Why is the (Zeff = Z - S) Equation is Not a Precise Measurement of ENC?

1. While the value of "Z" in Zeff = Z - S is known exactly, challenge lies in estimating value of "S"; 2. for simplicity, previously estimated "S" by assuming that each core electron contributes 1.00 to "S" and outer electrons contribute nothing; 3. However, more accurate approach (that includes valence electrons) was developed by John Slater, which is applied to elements that do not have e- in "d" or "f" subshells

What is an Example of Periodic Trend in Valence Electron Zeff Down a Group?

1. While we would expect the ENC experienced by the valence electrons in Li and Na to be about the same (Li = 3 - 2 = 1+ and Na = 11 -10 = 1+), ENC increases slightly down the group 2. In the case of the alkali metals, Zeff increases from 1.3+ for Li to 2.5+ for Na to 3.5+ for K

What is the Periodic Trend In Electronegativity Down a Group?

1. With some exceptions (especially in the transition metals), 2.electronegativity decreases with increasing atomic number in a group (down a column) 3. Explanation: this is what is expected, knowing that ionization energies decrease with increasing atomic number in a group and electron affinities do not change very much

What are the Periodic Trends in Atomic Radii Down a Group?

1. Within each group, bonding atomic radius tends to increase from top to bottom; 2. Explanation: This trend results primarily from the increase in the principal quantum number "n" of the outer electrons 3. (increasing # shells); 4. as you go down a column, outer electrons have a greater probability of being farther from the nucleus, causing atomic radius to increase

What are the Periodic Trends in Atomic Radii Across a Period?

1. Within each period, bonding atomic radius tends to decrease from left to right; 2. Explanation: major factor influencing this trend is increase in ENC (Zeff) across a period from left to right 3. (the increasing ENC steadily draws valence electrons closer to the nucleus, causing the bonding atomic radius to decrease)

What is the Third Discontinuity in Periodic Trend in Electron Affinity (Noble Gases)?

1. the addition of an e- to a noble gas requires that the e- reside in a higher-energy subshell that is empty in the atom; 2. Because occupying a higher-energy subshell is energetically unfavorable, the e- affinity is highly positive

What are the General Periodic Trends of Electronegativity?

Bottom left of periodic table: least electronegative Top right of periodic table: most electronegative

What is the Third Rule for the Electron Configuration of Ions?

If there is more than one occupied subshell for a given value of "n," the electrons are first removed from the orbital with the highest value of "l," (ex: a tin atom loses its 5p electrons before it loses its 5s electrons: