Relative Size Ionization Energy Electron Affinity Electronegativity.

Relative SizeIonization Energy

Electron Affinity

Electronegativity

General Rule - Relative Size

When looking at the periodic table, atoms get bigger:

Top to bottom Right to left

http://www.lung-cancer-report.com/berylliosis-beryllium/picture-of-beryllium-atom.html

Top to Bottom Down a Column

The atoms get bigger because the electrons are in

a higher energy level.

Left to RightAcross a Row

The atoms get smaller because the positive charge in the middle of

the atom is more concentrated so it’s sucking the electrons in closer.

Relative Size Chart

http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/atomic-radii.html

*Positive Ions and Negative Ions*

Positive Ions: If an atom loses all of its valence (outermost) electrons, it’s going down to the next energy level so it’s getting smaller.

Losing electrons = positive charge

More protons than electrons = + charge

*Positive Ions and Negative Ions*

Negative Ions: If an atom gains electrons it has a negative charge. The nucleus stays the same but the radius gets bigger because there are more electrons. Gaining electrons = negative charge More electrons than protons = -

charge

Sample Problems - Part 1

Which one has a larger radius?(a) Ti or Ni(b) F or F-1

(c) Ba or Hf(d) Ca or Ca+2

Sample Problems - Part 2

Which one has a smaller radius?

(a) K or Cs(b) Cs or Os(c) O or O-2

(d) Na or Na+1

Challenge

Excluding the Noble Gases becausethey’re special:What is the smallest atom? ____________________What is the largest atom?____________________

IonizationIonization EnergyEnergy

Definition: The energy required to remove Definition: The energy required to remove an electron from an atom.an electron from an atom.

First Ionization EnergyFirst Ionization Energy The energy needed to remove the most The energy needed to remove the most

loosely held electron from an atom.loosely held electron from an atom. Measured in kilojoules per mole (kj/mol).Measured in kilojoules per mole (kj/mol).

General Rule - General Rule - Ionization EnergyIonization Energy

Ionization Energy increases going Ionization Energy increases going across periods (rows) - increases as across periods (rows) - increases as atomic number increases.atomic number increases.

Ionization Energy decreases going Ionization Energy decreases going down groups (columns).down groups (columns).

Classifying Elements based Classifying Elements based on Ionization Energyon Ionization Energy

MetalsMetals Tend to lose electrons to become more Tend to lose electrons to become more

stablestable Low ionization energyLow ionization energy

•NonmetalsNonmetals•Tend to gain electrons to become more Tend to gain electrons to become more stablestable•High ionization energyHigh ionization energy

Noble GasesNoble GasesHave an octet so they’re already stableHave an octet so they’re already stableVery high ionization energyVery high ionization energy

Electron AffinityElectron Affinity

Definition: the attraction of an atom for an Definition: the attraction of an atom for an additional electronadditional electron

Metals tend to have low electron Metals tend to have low electron affinities.affinities.

Nonmetals tend to have high electron Nonmetals tend to have high electron affinitiesaffinities..

Sample Problems - Part 3Sample Problems - Part 3

Which one has a lower ionization energy?Which one has a lower ionization energy?

(a) Cl or Kr(a) Cl or Kr

(b) Iron or Iodine(b) Iron or Iodine Which one has a higher electron affinity?Which one has a higher electron affinity?

(a) Oxygen or Barium(a) Oxygen or Barium

(b) Na or Cl(b) Na or Cl

ElectronegativityElectronegativityDefinition: the relative attraction of an atom Definition: the relative attraction of an atom

for a shared pair of electrons.for a shared pair of electrons.

The difference in electronegativities The difference in electronegativities increases as the bond strength between increases as the bond strength between two atoms increases.two atoms increases.

• Metals tend to have low Metals tend to have low electronegativities.electronegativities.

• Nonmetals tend to have high Nonmetals tend to have high electronegativities.electronegativities.

Electronegativity ChartElectronegativity Chart

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are needed to see this picture.

www.monroecc.edu/wusers/flanzafame/PerElNegativity.pdf

Sample Problems - Part 4Sample Problems - Part 4

Which atom has a higher Which atom has a higher electronegativity?electronegativity?

(a) Ca or C(a) Ca or C(b) Titanium or Tellurium(b) Titanium or Tellurium

Which atom has a lower electronegativity?Which atom has a lower electronegativity?(a) Br or Be(a) Br or Be(b) Strontium or Selenium(b) Strontium or Selenium

Factors that affectFactors that affect Ionization Energy, Ionization Energy,

Electron Affinity, and Electron Affinity, and ElectronegativityElectronegativity

1.1. Distance from nucleusDistance from nucleus

2.2. StabilityStability

Connections between Connections between Ionization Energy,Ionization Energy,

Electron Affinity, andElectron Affinity, andElectronegativityElectronegativity

In general, as Electron Affinity increases, In general, as Electron Affinity increases, Ionization Energy increases.Ionization Energy increases.

Electron Affinity and Electronegativity Electron Affinity and Electronegativity increase going across a period (left to increase going across a period (left to right).right).

Ionization Energy and Electronegativity Ionization Energy and Electronegativity increase going up a column (bottom to increase going up a column (bottom to top).top).