Gen Cem MCAT chap 2

noble gases

VIIIA -inert gases (minimal reactivity fue to filled valence shell) -high ionization energies - little to no tendency to lose electrons or gain (for He, Ne, Ar) -no measurable electronegativites -low boiling points and exist as gases at room temp

transition metals

VIIIB metals and low electron affinites -hard, have high melting points and boiling points -malleable and good conductors due to loosley held e- that fill d-orbitas -many different possible oxidation states (capable of losing different numbers of e- fro s- and d- orbitals in valence shells - because of ability to attain different oxidation states, transition metals form many different ionic compounds -associates w/ water to form hydration complexes

electronegavity

a measure of the tendency of an atom to attract a bonding pair of electrons greater the force, the more it attracts an electron within a bond. -related to ionization energies - first 3 noble gases are the exception

effective nuclear charge (Zeff)

amount of charge felt by the most recently added electron - for elements in the same period, Zeff increases left to right as oe goes down a group, more subshells are added, which reduce the electrostatic attraction between the nucleus and the outer shell -increasingly positive nucleus cancels distance effect -electrons still held less tightly to nuclus up and right the bigger the number gets

electron affinity

exothermic (when an element steals a electron) energy dissipated by a gaseous species when it gains an electron (opposite concept from ionization energy) "ΔHrxn has a negative sign" but is reported as a positive number the greater the Zeff, the greater the energy release TREND: increases from left to right and down to up noble gases have no electron affinity metals have lo affinity

Chalcogens (VIA)

group 16 -eclectic group of nonmetals and metalloids. -not as reactive as halogens -each have 6 electrons in valence shells due to proximity to metalloids, have small atomic radii and large ionic radii -oxygen very important

halogens

group 17 -highly reactive nonmetals - volitile and vary in natural state (gas, liquid, solid) - chemical reactivity is more uniform due to high electronegativities and electron affinities(very reactive toward alkali and alkaline earth metals -F has highest electrongeativity -so reactive that they are found as ions (halides) or diatomic molecules

alkali metals

group IA or group 1 - posses most classic physica lproterties of metals, except density -only one loosley bound electron in outermost shell Zeff values very low, lare atom radii. - low ionization energy, low electron affinities, low electronegativity -easily loses one electron and reacts readily with nonmetals

alkaline earth metals

metallic elements in group 2 of the periodic table which are harder than the alkali metals and are also less reactive slightly higher effective nuclear charge, so smaller atomic radii 2 e- in valence shell, easily removed and allows divalent cations still really reactive

A elements

representative elements, paired with roman numeral and seen as Groups IA through VIIIA -have valence e- in s or P subshells

elements seek

stability and will often times revert to noble gases

oxidation state

the condition of an atom expressed by the number of electrons that the atom needs to reach its elemental form

first ionization energy

the energy required to remove the first electron from an atom first is easiest GiA and IIA have super low ionizations energies, called active metals (loss of 1 or 2 electrons forms more stable filled valence shell.) -active metals found in ionic compounds, minerals and ores

periodic law

the law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements

ionization energy MCAT expertise

"First ionization energy (IE) will always be smaller than second IE, which will always be smaller than third IE. However, the degree to which the IE increases provides clues about the identity of the atom. If losing a certain number of electrons gives an element a noble gas-like electron configuration, then removing a subsequent electron will cost much more energy. For example"

"Ionization energy contributes to an atom's chemical reactivity. Which of the following shows an accurate ranking of ionization energies from lowest to highest?"

"Ionization energy increases from left to right, so the first ionization energy of lithium is lower than that of beryllium. Second ionization energy is always larger than first ionization energy, so beryllium's second ionization energy should be the highest value. This is because removing an additional electron from Be+ requires one to overcome a significantly larger electrostatic force."

"Mendeleev's table was arranged by atomic weight, but the modern periodic table is arranged by:"

"The modern periodic table is arranged in order by atomic number."

"Lithium and sodium have similar chemical properties. For example, both can form ionic bonds with chloride. Which of the following best explains this similarity"

"The periodic table is organized into periods (rows) and groups (columns). Groups (columns) are particularly significant because they represent sets of elements with the same valence electron configuration, which in turn will dictate many of the chemical properties of those elements. Although (A) is true, the fact that both ions are positively charged does not explain the similarity in chemical properties; most metals produce positively charged ions"

"Which of the following elements has the highest electronegativity? Mg Cl Zn I"

"This question requires knowledge of the trends of electronegativity within the periodic table. Electronegativity increases as one moves from left to right for the same reasons that effective nuclear charge increases. Electronegativity decreases as one moves down the periodic table because there are more electron shells separating the nucleus from the outermost electrons. In this question, chlorine is the furthest toward the top-right corner of the periodic table."

"What is the highest-energy orbital of elements with valence electrons in the n = 3 shell? s-orbital p-orbital d-orbital f-orbital"

"When n = 3, l = 0, 1, or 2. The highest value for l in this case is 2, which corresponds to the d subshell. Although the 3d block appears to be part of the fourth period, it still has the principal quantum number n = 3. In general, the subshells within an energy shell increase in energy as follows: s < p < d < f (although there is no 3f subshell)."

families (groups)

columns on the periodic table have same electron configuration in valence shell and share similar chemical property

Roman numeral representation example

group VA means electron configuration of s2p3

characteristic of transition metals (group B elements)

have 2 or more oxidation states (charges when forming bonds with other atoms) -makes good conductors because valence electrons are loosely held to atom and are free to move

lanthanide series

in the periodic table, the f-block elements from period 6 that follow the element lanthanum -s and F subshells

actinide series

in the periodic table, the f-block elements from period 7 that follow the element actinium -s and f subshells

ionic radii

measured distance from the center of an ion to its outer electrons - metals lose e- and become positive - nonmetals gain e- and become negative - metalloids tend to stick with similar properties as wher they are found on table. - larger ionic radius means more needing of electrons for stability -metals close to metalloid like want to lose e- (more to lose) and thus ionic radii is smaller cation are generally smaller than corresponsding neutral atom anions are generally larger TREND: tends to increase going down a group

relationship between complementary colors and suntraction frequenceies

when light hits and object, it reflects the wavelength of the color it doesn't absorb. what we see is the complementary color. ex: carotene absorbs blue light, but relfectst other colors. interpret color of carotene as white light minus blue light, which makes it appear yellow/orange

alkali and alkaline metals

"Alkali and alkaline earth metals are both metallic in nature because they easily lose electrons from the s subshell of their valence shells."

"Metals are often used for making wires that conduct electricity. Which of the following properties of metals explains why?"

"All four descriptions of metals are true, but the most significant property that contributes to the ability of metals to conduct electricity is the fact that they have valence electrons that can move freely. Malleability, (A), is the ability to shape a material with a hammer, which does not play a role in conducting electricity. The low electronegativity and high melting points of metals, (B) and (D), also do not play a major role in the conduction of electricity."

"Carbon and silicon are the basis of biological life and synthetic computing, respectively. While these elements share many chemical properties, which of the following best describes a difference between the two elements?"

"As one moves from top to bottom in a group (column), extra electron shells accumulate, despite the fact that the valence configurations remain identical. These extra electron shells provide shielding between the positive nucleus and the outermost electrons, decreasing the electrostatic attraction and increasing the atomic radius. Because carbon and silicon are in the same group, and silicon is farther down in the group, silicon will have a larger atomic radius because of its extra electron shell."

"What determines the length of an element's atomic radius? The number of valence electrons The number of electron shells The number of neutrons in the nucleus" .

"Atomic radius is determined by multiple factors. Of the choices given, the number of valence electrons does have an impact on the atomic radius. As one moves across a period (row), protons and valence electrons are added, and the electrons are more strongly attracted to the central protons. This attraction tightens the atom, shrinking the atomic radius. The number of electron shells is also significant, as demonstrated by the trend when moving down a group (column). As more electron shells are added that separate the positively charged nucleus from the outermost electrons, the electrostatic forces are weakened, and the atomic radius increases. The number of neutrons is irrelevant because it does not impact these attractive forces."

atomic radii and ionic radii ket concept

"Atomic radius refers to the size of a neutral element, while an ionic radius is dependent on how the element ionizes based on its element type and group number."

"The properties of atoms can be predicted, to some extent, by their location within the periodic table. Which property or properties increase in the direction of the arrows shown?" up and to right

"Electronegativity describes how strong an attraction an element will have for electrons in a bond. A nucleus with a larger effective nuclear charge will have a higher electronegativity; Zeff increases toward the right side of a period. A stronger nuclear pull will also lead to increased first ionization energy, as the forces make it more difficult to remove an electron. The vertical arrow can be explained by the size of the atoms. As size decreases, the positive charge becomes more effective at attracting electrons in a chemical bond (higher electronegativity), and the energy required to remove an electron (ionization energy) increases."

"In each of the following pairs, which has the larger radius?: F or F- K or K+"

"F- > F; K > K+. The ionic radii of anions are larger than the associated atomic radii, while the ionic radii of cations are smaller"

"Why do halogens often form ionic bonds with alkaline earth metals? The alkaline earth metals have much higher electron affinities than the halogens. By sharing electrons equally, the alkaline earth metals and halogens both form full octets. Within the same row, the halogens have smaller atomic radii than the alkaline earth metals. The halogens have much higher electron affinities than the alkaline earth metals"

"Ionic bonds are formed through unequal sharing of electrons. These bonds typically occur because the electron affinities of the two bonded atoms differ greatly. For example, the halogens have high electron affinities because adding a single electron to their valence shells would create full valence shells. In contrast, the alkaline earth metals have very low electron affinities and are more likely to be electron donors because the loss of two electrons would leave them with full valence shells. (A) states the opposite and is incorrect because the halogens have high electron affinity and the alkaline earth metals have low electron affinity. (B) is incorrect because equal sharing of electrons is a classic description of covalent bonding, not ionic. (C) is a true statement, but is not relevant to why ionic bonds form."

"When dissolved in water, which of the following ions is most likely to form a complex ion with H2O? Na+ Fe2+ Cl- S2-"

"Iron is a transition metal. Transition metals can often form more than one ion. Iron, for example, can be Fe2+ or Fe3+. The transition metals, in these various oxidation states, can often form hydration complexes with water. Part of the significance of these complexes is that, when a transition metal can form a complex, its solubility within the related solvent will increase. The other ions given might dissolve readily in water, but because none of them are transition metals, they will not likely form complexes."

periodic trends

"Periodic Trends Left → Right Atomic radius ↓ Ionization energy ↑ Electron affinity ↑ Electronegativity ↑ Top → Bottom Atomic radius ↑ Ionization energy ↓ Electron affinity ↓ Electronegativity ↓ Note: Atomic radius is always opposite the other trends. Ionic radius is variable."

MCAT expertise

"Relating valence electrons to reactivity is important. Elements with similar valence electron configurations generally behave in similar ways, as long as they are the same type (metal, nonmetal, or metalloid)."

"Of the four atoms depicted here, which has the highest electron affinity?"

"The correct answer to this question may be surprising, because it illustrates an important exception to a trend. Electron affinity is related to several factors, including atomic size and filling of the valence shell. Atoms are in a low-energy state when their outermost valence electron shell is filled, so atoms needing only one or two electrons to complete their outer shell will have high electron affinities. In this example, (B) and (D) need only one more electron to have a full outer shell, so these two choices are strong contenders for the right answer. The other trend to consider is atomic radius. As atomic radius increases, the distance between the nucleus and the outermost electrons increases, thereby decreasing the attractive forces between protons and electrons. As a result, increased atomic radius usually leads to lower electron affinity. Because (B) is smaller, we would assume it would have the highest electron affinity. However, in this case, (B) corresponds to the atom fluorine, which has an unusually low electron affinity value due to its instability. Therefore, (D) is the correct answer. "

"Which of the following atoms or ions has the largest effective nuclear charge? Cl Cl- K K+"

"The effective nuclear charge refers to the strength with which the protons in the nucleus can pull on electrons. This phenomenon helps to explain electron affinity, electronegativity, and ionization energy. In (A), the nonionized chlorine atom, the nuclear charge is balanced by the surrounding electrons: 17 p+/17 e-. The chloride ion, (B), has a lower effective nuclear charge because there are more electrons than protons: 17 p+/18 e-. Next, elemental potassium, (C), has the lowest effective nuclear charge because it contains additional inner shells that shield its valence electron from the nucleus. (D), ionic potassium, has a higher effective nuclear charge than any of the other options do because it has the same electron configuration as Cl- (and the same amount of shielding from inner shell electrons as neutral Cl) but contains two extra protons in its nucleus: 19 p+/18 e-."

"Which of the following is an important property of the group of elements shaded in the periodic table below?" alkaline earth metals. "elements are the best electrical conductors in the periodic table. These elements form divalent cations. The second ionization energy for these elements is lower than the first ionization energy. The atomic radii of these elements decrease as one moves down the column." Excerpt From: Kaplan Test Prep. "MCAT General Chemistry Review 2021-2022." Apple Books.

"This block represents the alkaline earth metals, which form divalent cations, or ions with a +2 charge. All of the elements in Group IIA have two electrons in their outermost s subshell. Because loss of these two electrons would leave a full octet as the outermost shell, becoming a divalent cation is a stable configuration for all of the alkaline earth metals. Although some of these elements might be great conductors, they are not as effective as the alkali metals, eliminating (A). (C) is also incorrect because, although forming a divalent cation is a stable configuration for the alkaline earth metals, the second ionization energy is still always higher than the first. Finally, (D) is incorrect because atomic radii increase when moving down a group of elements because the number of electron shells increases."

"How many valence electrons are present in elements in the third period?"

"This question is simple if one recalls that periods refer to the rows in the periodic table, while groups or families refer to the columns. Within the same period, an additional valence electron is added with each step toward the right side of the table."

B elements

*nonrepresentative elements* also known as the *transition elements* have their valance electrons in the s and d subshells have two or more oxidation states - charges when forming bond with other atoms some (copper, nickel, silver, gold, palladium, platinum) are relatively nonreactive which makes them good for jewelry IB-VIIIB very low electron affinity, low ionization energy, low electronegativity very hard high boiling and melting points malleable good conductors different oxidation states correspond to the different colors can form hydration complexes with water

valence electrons

Electrons on the outermost energy level of an atom -greatest amount of potential energy -more involved in chemical bonds

metals

Elements that are good conductors of electric current and heat. left side and middle -active metals, transition mtals, lanth and actinide series -lustrous - high melting points and density -high malleability and ductile -defined by low effective nuclear charge, low electronegativity (high electropositivity) - large atomic radius, small ionic radius, - low ionization energy -low elecron affinity - all these characteristics are ability to easily give up electrons

nonmetals

Elements that are poor conductors of heat and electric current -brittle in solid state, show no luster -high ionization energies, electron affinities, electronegativiies - small atomic radii and large ionic radii -poor conductors of heat and electricity -all manafestations of inability to give up give up electrons easily

metalloids

Elements that have properties of both metals and nonmetals stair step -electronegativities and ionization energies lie between those of metals and nonmetals -all physical properties vary B, Si, Ge, As, Sb, Te, Po, At.

periods (rows)

From left to right across the periodic table.

atomic radii

Half the distance between the nuclei of identical atoms that are bonded together decreases as you move from left to right (more positive nucleus) increases going down and left

Pauling electronegativity scale

Ranges for Cs the lowest electronegativity of .7 (most electropositive) to F of most electronegativity of 4 increases going left to right and from down to up

ionization energy

The amount of energy required to remove an electron from an atom -endothermic process -greater the Zeff, the more energy needed -TREND: increases from left to right and from bottom to top