Periodic Trends

Atomic Size/Atomic Radius

-measured as the distance from the nucleus to the outermost electrons

Vertical trend for Atomic Size. Reason

Vertical(top/bottom)

• atoms become bigger from top to bottom. top(smaller), bottom(bigger)

Reason why atoms get larger vertically:

• (#1) AS atomic number(Z) increases, so do the #of protons, #of electrons, #of orbitals, and size of orbitals

• (#2) As atomic number(Z) increases, so do the number of inner electrons. ELectron shielding describes the ability of an atom’s inner electrons to shield its positvely-charged nucleus from its valence electrons. (check notes)

Effective Nuclear Charge

Effective (does its job well, its works well) Nuclear Charge (protons (+)

Symbol: Zeff

Zeff (squiggly =) Z (atomic number) - S (#of inner electrons)

• If Zeff is a large number, it means the nucleus is very effective, it pulls electrons inward and the atom is quite small

• If Zeff is a small number, it means the nucleus is not very effective, it does not pull the outer electrons, and the atom is large

• Zeff = the roman numeral

Horizontal trend for Atomic Size. Reason

Size of atom decreases from left to right, contradictory to what is seen vertically: Z increases, # of protons increases #of electrons increase, but the size SHRINKS.

• read notes

Metallic Character

Horizontally: metallic character increases from right to left across the table. left (metals), right (nonmetals)

Vertically: metallic character increases from top to bottom in mixed families (IVA, VA, VIA) - mixed families) top: nonmetals, bottom: metals

How can one metal be more metallic than another metal?

All due to reactivity

• A very metallic metal is very reactive, which means it is very willing and gives up its electrons readily.

• Large Metallic Atoms are the most metallic metal atoms due to their loose grip they have on their electrons

Ionic Size/Ionic Radius

• Cations are always smaller than the parent atom that they come from.

  • the loss(decrease in size) of an electron from the structure

  • The Protons outnumber the number of remaining electrons so this strengthens the power of the nucleus

  • nucleus is capable of bringing in remaining electrons in close to itself

• Anions are larger than the parent atom that they come from.

  • by gaining an electron, it implies an increase

  • the number of electrons outnumber the number of protons

  • the nucleus loses some of its power and grip becomes loose so anion is larger now than when atom was neutral.

  • anions “spread out” to accomodate extra electrons which cause increase in repulsion, this spreading-out minimizes the repulsion

Trends in Ionic Size/Ionic Radius

Vertically: the sizes of the ions is parallel to the sizes of the neutral atoms

• Top: smaller

Bottom: Larger

for both (gaining/losing an electron does not change the number of inner electrons so they state same pattern change or neutral)

Horizontally: the general overall trend increases in ionic size from left to right

left: cation formation (smaller)

right: anion formation (larger)

Ionization Energy

Ionization - The formation of an ion, specifically a cation
Energy goes in, atom loses an electron, cation formation

Ionization Energy - the amount of energy that is REQUIRED for an atom to lose an electron (endothermic process)

High IE = difficult electron removal (“costs a lot”)

Low IE = easy electron removal (“does not cost a lot”)

Trends in Ionization Energy

Horizontally:

• Left
  Lowest IE, group IA, biggest, weakest ZEFF, metals (natural tendency to lose electron)

• Right
  Highest IE, group VIIIA, smallest, strongest Zeff, most stable

Vertically:

IE increases from bottom to top in a family

• Top (small) few inner electrons, nucleus has tighter grip

• Bottom(large) many inner electrons, nucleus has loose grip

ex. At Nitrogen (1402 IE) Oxygen (1314), 2p3 to 2p4, goes down as it has 3 half filled compartments, more stable and doesn’t want to lose its stability by giving away an electron (check notes on what I typed, and how to do IE equation).

Electron Affinity

(a liking for) all about a liking for electrons, but the Actual Defintion is:
It is the energy change that is involved when an atom receives an electron(becomes an electron)
process: electron goes in atom( energy comes out - exothermic process) becomes anion

Trends in Electron Affinity

Horizontally:
Electron Affinity increases from left to right
Left
Metals, IA, energy change not favorable, endothermic metals, cannot and should not receive electrons, makes them unstable

Right
-nonmetal VIIA, energy change is very favorable, exothermic nonmetals are receptive to anion formation, set stable configuration by doing so. Halogens have highest electron affinity of entire P.T.

Vertically:
Electron Affinity increases from bottom to top
Top: Highest EA
Bottom: Lowest EA (least exothermic, grip gets loose)

• same ZEFF, but the distance from nucleus to outer electron increases going down, size increases.
  

Electronegativity

-the ability of an atom to pull electrons in close to itself while it is involved in a chemical bond with another atom

• Think of it as a “Tug of War” for electrons

• The atom that is more electronegative is capable of bringing the electrons closer to itself (winner of the tug of war for electrons)

Trends in Electronegativity

Horizontally increases from left to right
Left
metals, no need/want for electrons, lose electrons to get stable configuration
Right
always seeking electrons to get stable config.

Vertically increases from bottom to top
Top - small
Bottom - large

• Zeff same, but the nucleus is larger further down, less grip

• Fluorine is the most electronegative atom and mose reactive of entire P.T

• oxygen is 2nd place most electronegative, and reactive