Ch 9 - Periodicity and Ionic Bonding

How do valence electrons display in electron configurations?

periodicity

core electrons

all the electrons that are not valence electrons

What is the size of atoms determined by?

• the electronic structures

• the interactions between the oppositely charged nucleus and electrons

electrostatic principles

1. oppositely charged particles attract each other 

2. like-charged particles repel 

3. as charges increase so does the attraction or repulsion

4. as the two charged bodies get closer to each other, the force of attraction or repulsion gets stronger  

effective nuclear charge (Z_eff)

the net positive charge from the nucleus that an electron experience

the effective nuclear charge equation

Z_eff = Z - S

z = the number of protons 

s = shielding by the other electrons 

What happens to Z_eff across a row of the period table?

in increases

What happens to Z_eff going down a group?

it decreases

atomic radius

one half the distance between the nuclei of 2 identical atoms that are joined by a covalent bond 

do cations have bigger or smaller radii in comparison to their neutral atoms?

smaller 

do anions have bigger or smaller radii in comparison to their neutral atoms?

bigger 

ionization energy

the energy required to remove an electron from a gaseous atom and produce a gaseous cation

What happens to IE when the radius size decreases?

it increases

electron affinity

the energy change when an electron is added to a gaseous atom to form a gaseous anion

what do negative EA represent?

a decrease in energy when an electron is added to a gas phase atom (exothermic)

What do positive EA represent?

reflect endothermic process, as energy is needed to add electrons to an atom

ionic lattice 

the 3D structure of ionic compounds, where the cations and anions are held together by electrostatic attractions 

lattice energy 

the energy released when gas phase ions are converted into a solid compound 

how can lattice energy be calculated?

by adding the interactions between oppositely charged particles in the solid (Hess’s Law)

• IE

• EA

• bond energy (BE)

• enthalpy oy sublimation 

What happens to lattice energy ion size increases? what does this mean?

it decreases, meaning less energy is released when larger ions form compounds

the PE of two interacting charged particles (E_el)

inversely proportional to the distance between the centers of the two particles (d)