Lesson 4: The Periodic Table
True or false: A reaction between water and sodium is a relatively nonviolent reaction?
False: group IA metals react highly and violently with water and air. They are typically not found in neutral forms in nature; instead bonded to a nonmetal.
Would alkaline earth metals or halogens be most likely found in nature as anions?
1A and 2A are the active metals; they have such low ionization energy due to their high electropositivity and large amount of electron shielding, and the loss of electrons from their valence shell means achieving a stable octet. So they typically exist in cationic forms. Halogens are much more against giving up their electrons, and thus mainly exist as anions since accepting one more electron is worth achieving a stable octet.
What are the two large classes of elements?
A elements "representative elements" are those in groups IA to VIIIA that include valence electrons in orbitals of either s or p subshells. B elements "nonrepresentative" are transition elements (valence electrons in orbitals of s and d subshells) and the lanthanide and actinide series (valence electrons in orbitals of s and f subshells). *Lanthanides are on top and Actinides are on bottom.
A new element has been discovered. It has a low effective nuclear charge, is lusterous and ductible, has a large atomic radius, low ionization energy, and low electron affinity. What type of element would this likely be, and provide reasoning for your answer based on each of these characteristics.
A metal. Metals have luster (shine), and they can be deformed without breaking (ductible). They also have typically large atomic radii because of the lower power to attract electrons and thus have valence electrons that do not require as high an ionization energy to leave the compound.
A copper wire is an excellent conductor of electricity and heat. Explain why the nonreactivity of this element - which is also used to make pennies - is unique for this class of elements.
A typical B element has a large atomic radius that allows the valence electrons in the transition element atom's outermost s and d or f shells freedom to move and conduct electricity. Therefore, while this can make some of these elements quite reactive, there are some unique ones like Ni and Pd that are unreactive.
Describe the trend of Zeff down Group IIA using electron shielding.
As the principal quantum number increases, the electrons in the valence shell are held less tightly because the inner shell electrons shield much of the electrostatic force from the positively charged nucleus via their own negative repulsive force. This shielding is even enough to overcome the increasing positivity of the nucleus via a rise in atomic number. So Zeff essentially remains constant, but increases in atomic radii are noticed both by virtue of the increased electron shielding from the increase in inner shells.
Differentiate between atomic radii and ionic radii.
Atomic radii takes into account the effect of the electrostatic forces from the positively charged nucleus and is largely defined based on how much that is overcome based on atomic number increases. Ionic radii is defined largely by distance from the metalloid line and the generalizations that metals lose electrons to achieve octets and nonmetals gain electrons to achieve octets, while metalloids go either way. Therefore, the less metallic a metal is (closer to metalloid line), the more electrons they need to lose, and the smaller the ionic radii is (what the stabler ion would look like if it lost all those electrons). For nonmetals, the less nonmetallic a nonmetal is (closer left to the metalloid line) the more electrons it must gain for its ion to achieve a stable octet, and the larger the ionic radii is (what the stabler ion would look like if it gained the electrons necessary to achieve octet).
Which periodic trend is essentially opposite of all others and how so?
Atomic radius increases going down and to the left, whereas all other periodic trends increase going up and to the right.
Would it require a higher ionization energy to excite an electron on C or Li?
Because nonmetals have higher ionization energies, C would definitely require a higher frequency photon of light to emit a photoelectron. This is attributed to their electron configurations: nonmetals don't want to lose electrons because that takes them farther away from achieving an octet then it would be just to gain electrons.
Compare the Zeff values of elements in Group IA to elements of other groups, and how these values correlate to the trends of these elements regarding electronegativity, electron affinity, and ionization energy.
Because of only having one loosely bound electron in the outermost shell and the lowest atomic number across all principal quantum numbers, alkali metals have very low Zeff values. This is what influences the lower energy required to remove an electron (low IA), the less exothermic - actually requiring an input of energy - when considering gaining an electron (low electron affinity), and the decreased power and desire to attract electrons since losing only one electron would give elements of this group a stable octet.
What can be concluded about the effective nuclear charge present in C atoms vs O atoms?
Because the Oxygen atom has a greater positive charge due to the larger atomic number, the electrons occupying the orbitals of the valence shell will be drawn closer to the nucleus. This causes the greater electrostatic attraction known as a greater effective nuclear charge, which offsets the repulsion that the electrons in lower energy levels may apply. Think F = Ke(q1q2/r^2)
How is the concept of complimentary colors related to transition-metal complexes abilities to showcase characteristic colors?
Because the formation of transition metal complexes permits the formation of high energy d orbitals, certain energy levels are able to be absorbed that otherwise wouldn't be, which causes any light frequencies not absorbed to be seen as color. Like with complimentary colors, the absorption of red would influence the display of its complimentary cyan color; the result of white light minus the frequency of absorbed red light.
Why can transition metals have different oxidation states?
Because they can lose different numbers of electrons from the s AND d orbitals that make up their valence shell.
Hypothesize why valence electrons have the highest potential energy of all an atom's electrons.
Because they occupy the energy shell furthest away from the nucleus, they both are held less tightly from the nucleus and experience electron-repulsion from the lower energy shell levels, both of which provide a tendency for valence electrons to interact with valence electrons of other atoms.
Provide reasoning as to what makes alkali and alkaline earth metals metallic with regards to the atomic level?
Being that metals only need to lose a few electrons to achieve a full octet, they have a much lower power to attract electrons (low electronegativity) and thus a far greater tendency to give away electrons form the s subshell to achieve a stable electron configuration. It also helps that a metal has a large atomic radius and thus loosely bonded valence electrons, as well as a low ionization energy.
How are energy levels and valence electrons denoted by the periodic table?
Descending down each row of the periodic table involves increasing one principal quantum number/energy level. Going across each group signifies the number of electrons when the d block transition metal groups 3-12 are ignored.
True or false; a typical ionic bond occurs between a low IE and low EA element
False; low IE elements like Li would rather lose an electron and react with a high EA element like F, who wants to gain an electron to achieve a noble gas e configuration.
Compare and contrast the two groups of active metals.
Group IA metals differ from Group IIA metals only by their slightly greater Zeff and slightly larger atomic radius. Both are highly reactive and not typically found in natural state.
How does mercury differ from a standard metal?
Hg is the only metal that is liquid under standard conditions.
Explain the differences in trends of ionization energy and electron affinity in terms of change in enthalpy.
Losing an electron requires an input of heat, which is why ionization energy is a part of an endothermic process. Electron affinity is about an atom's greediness to gain an electron, which involves the release of energy; making it an exothermic process. Electron affinity is the literal numerical and conceptual opposite of ionization energy.
Why would the typical natural state of noble gases make them better suited as lighting sources vs a halogen?
Noble gases are much less reactive than halogens due to their stable electron configuration and therefore little to no electronegativity and very low most likely endothermic electron affinity. Halogens on the contrary are very reactive, and are often found in a diatomic state in nature with high electron affinities and electronegativities, which they use to react with the alkali and alkaline earth metals readily.
Explain why nonmetals are poor conductors of electricity using valence electrons.
Nonmetals have a high electronegativity (power of atoms to attract/want to attract electrons to itself) because doing so is a much easier method for establishing an octet then it would be to lose electrons. Therefore, nonmetals hold on to their valence electrons much more tightly, and thus they aren't given as much freedom to move and react as compared to metals.
With regards to the periodic table, what can be said for reactivity comparisons between Li and Na as compared to elements Li and Be?
Since Li and Na are in the same group/have the same number of electrons, their chemical reactivity is similar. This is also reinforced because they are the same type of element (metals).
Why is atomic radius of a single atom incapable of being measured?
Since electrons of an atom are constantly moving, they can never form an accurate outer boundary. Therefore the radius comes from halving the distance between two atoms of an element in contact with each other.
Which element would make a good semi-conductor and why? A). Li B). Tc C). Se D.) Te
Tellurium because it is a metalloid, which typically share metal and nonmetal properties. Having partial conductivity and ability to handle heat would make Tellurium the best choice.
How does the modern periodic table demonstrate the periodic law better than the first periodic table as organized by Mendeleev?
The first periodic table ordered elements based on atomic weight. The modern periodic table instead organizes elements by atomic number, which agrees with the periodic law that an element's number of protons and electrons is periodically dependent on the chemical and physical properties of that element.
What sections of the periodic table are metals?
The leftside active metals, the middle transition metals, and the lanthanide and actinide series.
Describe the generalization regarding toxicity as one moves down Group 16 in the periodic table.
The lighter chalcogen elements are relatively nontoxic and crucial for biological functions. The further down the group, the heavier and more metallic the element, and thus the more toxic and damaging the element - despite its biological usefulness.
What does a more or less exothermic reaction regarding the gain of an electron to an atom's valence shell imply about the resulting anion's stability?
The more exothermic the electron affinity (the greater energy loss with gain of an electron; high electron affinity) implies a greater decrease in the potential energy of the valence electrons of an atom, and thus a more stabler ion than previously. For those atoms with low enough electron affinities, this process can be so low exothermically that it becomes an endothermic process to gain an electron, which would imply that the anion formed when that atom gains an electron is less stable than its former.
Explain the tendency for transition metals to form many different colored ionic compounds using the concept of oxidation states.
Transition metals have s and d orbitals in their valence shell, which can both lose electrons to form cations that have different chemical properties and show as different colors.
True or False: Noble gases have high ionization energies
True: they are unwilling to disrupt their stable electron configuration by giving up an electron.
Ture or false: an electron affinity of -60 kj/mol implies a stabler anion than an atom with an electron affinity of 21 kj/mol?
True; the more negative electron affinity indicates more energy was lost to achieve a stabler anion. The positive electron affinity indicates that energy was inputted to achieve this anion, which means an anion with a higher potential energy, and a less stable ion altogether.