Chapter 2 - Kaplan MCAT Gen Chem Review

2025-2026

periods of periodic table

rows

groups of periodic table

columns

groups of periodic table have similar

chemical properties

valence electrons determine

chemical reactivity and properties of element

roman numeral represents the

number of valence electrons in neutral state

periodic table groups roman numerals from left to right

IA IIA IIIB IVB VB VIB VIIB VIIIB VIIIB VIIIB IB IIB IIIA IVA VA VIA VIIA VIIIA

/

1A 2A 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 3A 4A 5A 6A 7A 8A

2 rows of periodic table separated

lanthanides and actinides

A elements

-representative elements

-valence electrons in s or p

B elements

-nonrepresentative elements

-transition elements: valence electrons in s and d

-lanthanide or actinide series: valence electrons in s and f

metals

metalloids

nonmetals

metals are good conductors bc

valence electrons are free to move

metals

-low effective nuclear charge

-low electrogegativity

-large atomic radius

-small ionic radius

-low ionization energy

-low electron affinity

nonmetals

-high electronegativity

-small atomic radius

-large ionic radius

-high ionization energy

-high electron affinity

metalloids

-electronegativities and ionization energies lie between metals and nonmetals

-varying physical properties

Z_eff

-effective nuclear charge

-electrostatic attraction between the valence shell electrons and the nucleus

Z_eff ____ from left to right in a period

increases

Z_eff ___ within a group

is somewhat constant

as principal quantum number increases, outermost electrons…

are held less tight

atomic radius

one half the distance between the centers of 2 atoms of an element that are briefly in contact with each other

atomic radius ____ from left to right across a period

decreases

atomic radius ___ down a group

increases

2 generalizations about ionic radii

1. metals lose electrons and become positive

2. nonmetals gain electrons and become negative

nonmetals close to metalloid line have ____ ionic radius

larger (gain electrons while nucleus keeps same charge)

metals closer to metalloid line have _____ ionic radius

smaller (have more electrons to lose)

ionization potential / ionization energy

the energy required to move an electron from a gaseous species

IE

ionization energy

endothermic

input of heat

the greater the Z_eff, or closer the valence electrons to nucleus…

the more tightly bound they are

ionization energy ____ left to right across a period

increases

ionization energy ____ down a group

decreases

first ionization energy

-the energy necessary to remove the first electron

-then there’s second ionization, and so on

active metals

-elements in group IA and IIA

-low ionization energies

-always found as ionic compounds minerals or ores

exothermic

expel energy in form of heat

electron affinity

the energy dissipated by a gaseous species when it gains an electron

delta H_rxn is (negative/positive)

negative

electron affinity is (negative/positive)

positive

electron affinity ____ left to right across a period

increases

electron affinity _____ down a group

decreases

noble gases have electron affinities to the order of ___

zero

electronegativity

measure of the attractive force that an atom will exert on an electron in a chemical bond

greater the electronegativity, the more…

it attracts electrons within a bond

electronegativity correlates to

ionization energy (lower ionization energy, lower electronegativity)

first 3 noble gases are exceptions

pauling electronegativity scale

ranges from .7 to 4.0

electronegativity _____ left to right across a period

increases

electronegativity _____ down a group

increases

alkali metals

-group IA

-lower densities than other metals

-low Z_eff

-easily lose one electron

-react readily w nonmetals

low Z_eff

-large atomic radius

-low ionization energies

-low electron affinity

-low electronegativity

alkaline earth metals

-group IIA

-share most characteristics of alkali metals (higher effective nuclear charges=smaller atomic radii)

-easily lose 2 electrons

chalcogens

-group VIA

-nonmetals and metalloids

-smaller atomic radii, large ionic radii

-toxic/damaging at high concentrations

halogens

-group VIIA

-highly reactive nonmetals

-often gain 1 electron

-range from gas to liquid to solid

-high electronegativity, high electron affinity especially to IA and IIA

-found as halides (ions) (diatomic molecules)

noble gases

-VIIIA

-inert gases

-minimal chemical reactivity

-high ionization energy, no electronegativity

-low boiling point, gas at room temp

transition metals

-group B

-low electron affinities, low ionization energies, low electronegativities

-hard, high melting+boiling points

-malleable, good conductors

-oxidation states

-associate in solution w molecules of water or w nonmetals

why are transition metals good conductors

loosely held electrons

oxidation states

different possible charged forms, often correlated to different colors

formation of hydration complexes causes

d-orbitals to split into 2 energy sub levels

if an object absorbs a given color of light and reflects all others, our brain mixes these ____ and we perceive the complimentary color of the frequency that was absorbed

subtraction frequencies