MCAT General Chemistry - The Periodic Table

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Periodic Table of the Elements (PT)

ordering of the known elements by atomic weights/number; reveals a pattern of periodically recurring physical/chemical properties

periodic law

the chemical and physical properties of the elements are dependent, in a periodic way, upon their atomic numbers

periods

rows of PT; 7 representing the first 7 principal quantum numbers; each element in a given period has one more proton and one more electron than the element to its left

groups/families

columns of PT; Groups contain elements that have the same electronic configuration in their valence shell and share similar chemical properties

may be named by Roman numeral of valence electrons and split into A/B classes OR 1-18 (modern IUPAC stanadard)

valence shell

outermost shell of electrons

valence electrons

The electrons in the valence shell, farthest from the nucleus and having the greatest amount of potential energy; can form bonds with valence electrons of other atoms

A/representative elements

valence electrons in s or p subshells

IA - VIIIA

B/nonrepresentative elements

include both the transition elements and the lanthanide and actinide series; may have unexpected electron configurations

transition elements

have valence electrons in the s and d subshells; can have multiple oxidation states due to losing different numbers of s and d electrons

(Groups IB-VIIIB/3-12)

some (Cu, Ni, Ag, Au, Pd, Pt) are particularly nonreactive

lanthanide and actinide series

have valence electrons in the s and f subshells

metals

lustrous solids* with high melting points, high densities^; can be deformed without making; good conductors

low effective nuclear charge, low electronegativity (high electropositivity), large atomic radius, small ionic radius, low ionisation energy, low electron affinity

left and middle of PT

*except mercury (liquid @ RT)
^excpet lithium (half that of water)

lustrous

shiny

malleability

ability of metal to be hammered into shapes

ductility

ability to be pulled or drawn into wires

oxidation states

charges when forming bonds with other atoms

conductor

can transmit heat and electricity

i.e. metals are good conductors because of their loose, free-moving valence electrons

active metals

valence electrons found in s subshell

do not exist naturally in neutral forms; always found in ionic compounds/minerals/ores

nonmetals

brittle and dull when solid; poor conductors; less unified in chemical and physical properties than metals

high electronegativity (low electropositivity), small atomic radius, large ionic radius, high ionisation energy, high electron affinity

upper right of PT

*except mercury (liquid @ RT)
^excpet lithium (half that of water)

metalloids/semimetals

physical properties vary widely

chemical properties between metals and nonmetals; reactivities depend on elements with which they are reacting

staircase btwn metals and non-metals (B, Si, Ge, As, Sb, Te, Po, At)

effective nuclear charge (Zeff)

electrostatic attraction between the valence shell electrons and the nucleus

increases along period; largely stable along group

noble (inert) gases

have a full octet; minimal chemical reactivity; high ionisation energies and no measurable electronegativities

Group VIIIA/18

atomic radius

equal to one-half of the distance between the centers of two atoms of an element that are briefly in contact with each other

decreases along period; increases along group

ionic radii

1. metals lose electrons and become positive, while nonmetals gain electrons and become negative

2. metalloids can go in either direction, but tend to follow the trend based on which side of the metalloid line they fall on. (Si behaves more like a nonmetal, while (Ge) tends to act more like a metal)

non-metal ions closest to metalloid staircase are largest
metal ions closest to metalloid staircase are smallest

Ionization energy (IE)/ionization potential

energy required to remove an electron from a gaseous species

subsequent removals will require increasing amounts of energy

increases along a period, decreases along a group

Electron affinity

to the energy dissipated by a gaseous species when it gains an electron (reported as a positive number)

increases along a period; decreases along group

Electronegativity

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

increases along a period; decreases along group

Alkali metals

possess most of the classic physical properties of metals, except that their densities are lower than those of other metals; only one loosely bound electron in their outermost shells - form monovalent cations

Group IA/1

Alkaline earth metals

possess most of the classic physical properties of metals; two electrons in their outermost shells - form divalent cations

Group IIA/2

Chalcogens

eclectic group of nonmetals and metalloids; some are crucial for normal biological functions, the rest are metallic and toxic, and all are toxic in high doses

Group VIA/16

Halogens

highly reactive nonmetals with seven valence electrons; multiple states of matter; so reactive only found as ions or diatomic molecules

Group VIIA/17

halide

anion of halogens

hydration complexes

complex ions interactions with water

compex ions

Any ion in which a central metal atom (normally a transition element) is surrounded by a group of ions or molecules (ligands)

known for varied bright colors; absorbs certain frequencies of light

subtraction frequencies

light reflected or not absorbed by an object that gives the object its color

complementary color to the frequency that was absorbed

complementary color

‘opposite’ colour, as in a colour wheel