Periodic Trends

Effective Nuclear Charge (Zeff)

is the nuclear charge felt by an electron when both the actual nuclear charge (Z) and the repulsive effects (shielding) of the other electrons are taken into account (how attracted to the nucleus an electron is)

Shielding

when the inner electrons push away the valance electrons

Electrons ____ each other

repel

Down a group shielding ____

increases due to increased electron layers.

Across a period shielding ____

decreases due to the same amount of shielding and higher nucleus pull

Zeff ___ as you go down a group

decreases due to the excess shielding

Zeff ___ as you go across a period

increases due to stronger nucleus

Atomic Radius

half the distance between an the nuclei of adjacent atoms

Atomic Radius ____ down a group

increases due to more shells

Atomic Radius ___ across a period

decreases since distance is less due to stronger attraction to the nucleus

Ionic Radius

is the radius of a cation or an anion.

Ionic Radius/Size depends on

nuclear charge and number of electrons

Ionic Radius in cation is ___

smaller than a neutral atom

Ionic Radius in anion is ___

larger due to the more electrons repelling each other

Ionization Energy

the minimum amount of energy required to remove a valance electron from the gaseous state of an atom/ion

Ionization energy ____ going down a group

decreases since electrons are easier to remove

Ionization energy ____ going up a period

increases since electrons are harder to remove

Ionization energy trends are broken between

groups 2 & 3 and groups 5 & 6

Electron Affinity

the negative of the energy charge that occurs when an electron is accepted by an atom in the gaseous state from an anion; when it can attract an electron easier

When delta heat is positive

heat is put in

When delta heat is negative

heat is put out

To remove an electron

put in heat

To add an electron

take out heat

Down a column it becomes ____ to input an electron

harder, the farther you are from the nucleus, the weaker its pull it

Across a period it becomes ___ to input an electron

easier, a stronger nucleus gives it higher affinity

Exceptions for electron affinity

between groups 1 and 2 since it is easier to insert an electron into a lower subshell and 5 and 6 since it is easier to put an electron in its own orbital

Insert an electron into

lower energy subshell or own orbital

Electronegativity

the ability of an electron to attract itself to the electrons in a covalent bond

What happens with electrons in a covalent bond

they are shared

High electronegativity =

high ionization energy + high electron affinity

High electronegativity

wants electrons

low electronegativity

does not want new electrons

higher electronegativity is found

up a column and across (towards the right) a period

Element with most electronegativity

Florine

Element with second most electronegativity

Oxygen

Element with third most electronegativity

Nitrogen and chlorine are tied

Most reactive metals

Group 1A - alkali metals

Alkali metals are most reactive with

water

Alkali metals form bonds with oxygen in 

2/1 ratio

Least reactive elements are

Group 7A - halogens

Halogens gain ___ electrons in a reaction

1

_____ are the counterpart of Group 1A

Halogens

Metallic Characters

usually have low ionization energies - easy to ionize and have low electron affinities - dont want new electrons

Metallic character traits increase as you go

left and down the periodic table

The most metallic element

Fr - Francium

As shell number increases

distance from nucleus increases

Pure Covalent

electronegativity difference between 0 and 0.4/0.5

Pure Ionic

electronegativity difference greater than 1.6/1.7

Polar Covalent

electronegativity difference between 0.5 and 1.6/1.7