Trends in the Trends in the Periodic TablePeriodic Table

Atomic RadiusAtomic Radius Atomic radius is simply the radius of the atom, an indication of the Atomic radius is simply the radius of the atom, an indication of the

atom's volume.atom's volume. Atomic radius is one-half the distance between the two nuclei in a Atomic radius is one-half the distance between the two nuclei in a

molecule consisting of two identical atoms. molecule consisting of two identical atoms.

Trends in Atomic Size cont.Trends in Atomic Size cont. GroupGroup - atomic radius increases as you go down a - atomic radius increases as you go down a

group.group. WhyWhy? ? There is a significant jump in the size of the There is a significant jump in the size of the

nucleus (protons + neutrons) each time you move nucleus (protons + neutrons) each time you move from period to period down a group.from period to period down a group.

Additionally, new energy levels of electrons clouds Additionally, new energy levels of electrons clouds

are added to the atom as you move from period to are added to the atom as you move from period to period down a group, making the each atom period down a group, making the each atom significantly more massive, both in mass and significantly more massive, both in mass and volume.volume.

- - PeriodPeriod - atomic radius decreases as you - atomic radius decreases as you go from left to right across a period.go from left to right across a period.

WhyWhy? Stronger attractive forces in atoms ? Stronger attractive forces in atoms

(as you go from left to right) between the (as you go from left to right) between the opposite charges in the nucleus and opposite charges in the nucleus and electron cloud cause the atom to be electron cloud cause the atom to be 'sucked' together a little tighter.'sucked' together a little tighter.

Trends in Atomic SizeTrends in Atomic Size

Ionization EnergyIonization Energy

Ionization energy is the Ionization energy is the amount of energy required to amount of energy required to remove the outermost remove the outermost electron/s.electron/s.

Ionization energy is closely Ionization energy is closely

related to electronegativity.related to electronegativity.

Ionization Energy Trends cont.Ionization Energy Trends cont.

GroupGroup - ionization energy decreases - ionization energy decreases as you go down a group. as you go down a group.

WhyWhy? The shielding affect makes it ? The shielding affect makes it easier to remove the outer most easier to remove the outer most electrons from those atoms that electrons from those atoms that have many electrons (those near the have many electrons (those near the bottom of the chart).bottom of the chart).

Ionization Energy Trends Ionization Energy Trends

PeriodPeriod - ionization energy increases as you go - ionization energy increases as you go from left to right across a period. from left to right across a period.

WhyWhy? Elements on the right of the chart want to ? Elements on the right of the chart want to take others atom's electron (not given them up) take others atom's electron (not given them up) because they are close to achieving the octet. because they are close to achieving the octet. The means it will require more energy to remove The means it will require more energy to remove the outer most electron. Elements on the left of the outer most electron. Elements on the left of the chart would prefer to give up their electrons the chart would prefer to give up their electrons so it is easy to remove them, requiring less so it is easy to remove them, requiring less energy (low ionization energy).energy (low ionization energy).

ElectronegativityElectronegativity

Electronegativity is an Electronegativity is an atom's 'desire' to atom's 'desire' to grab another atom's grab another atom's electrons.electrons.

Electronegativity Trends cont.Electronegativity Trends cont. GroupGroup - electronegativity decreases as you go - electronegativity decreases as you go

down a group. down a group. WhyWhy? Elements near the top of the period table ? Elements near the top of the period table

have few electrons to begin with; every electron have few electrons to begin with; every electron is a big deal. They have a stronger desire to is a big deal. They have a stronger desire to acquire more electrons. Elements near the acquire more electrons. Elements near the bottom of the chart have so many electrons that bottom of the chart have so many electrons that loosing or acquiring an electron is not as big a loosing or acquiring an electron is not as big a deal. This is due to the shielding affect where deal. This is due to the shielding affect where electrons in lower energy levels shield the electrons in lower energy levels shield the positive charge of the nucleus from outer positive charge of the nucleus from outer electrons resulting in those outer electrons not electrons resulting in those outer electrons not being as tightly bound to the atom.being as tightly bound to the atom.

Electronegativity TrendsElectronegativity Trends PeriodPeriod - electronegativity increases as you go - electronegativity increases as you go

from left to right across a period. from left to right across a period. WhyWhy? Elements on the left of the period table ? Elements on the left of the period table

have 1 -2 valence electrons and would rather give have 1 -2 valence electrons and would rather give those few valence electrons away (to achieve the those few valence electrons away (to achieve the octet in a lower energy level) than grab another octet in a lower energy level) than grab another atom's electrons. As a result, they have low atom's electrons. As a result, they have low electronegativity. Elements on the right side of electronegativity. Elements on the right side of the period table only need a few electrons to the period table only need a few electrons to complete the octet, so they have strong desire to complete the octet, so they have strong desire to grab another atom's electrons.grab another atom's electrons.

ReactivityReactivity

Reactivity refers to how likely orReactivity refers to how likely or

vigorously an atom is to react vigorously an atom is to react with other substances. with other substances.

This is usually determined by This is usually determined by two things:two things:

1) How easily electrons can be 1) How easily electrons can be removed (ionization energy) removed (ionization energy)

from an atomfrom an atom

2) or how badly an atom wants 2) or how badly an atom wants to take other atom's electrons to take other atom's electrons

(electronegativity)(electronegativity)

The transfer/interaction of The transfer/interaction of electrons is the basis of chemical electrons is the basis of chemical

reactions.reactions.

Period - reactivity decreases as you go from left to right across a period.

Group - reactivity increases as you go down a group

Why? The farther to the left and down the periodic chart you go, the easier it is for electrons to be given or taken away, resulting in higher reactivity.

Reactivity of MetalsReactivity of Metals

Period - reactivity increases as you go from the left to the right across a period. Group - reactivity decreases as you go down the group.

Why? The farther right and up you go on the periodic table, the higher the electronegativity, resulting in a more vigorous exchange of electron.

Reactivity of Non-MetalsReactivity of Non-Metals

Ionic Radius vs. Atomic Ionic Radius vs. Atomic RadiusRadius

Metals - the atomic Metals - the atomic radius of a metal is radius of a metal is generally larger than generally larger than the ionic radius of the the ionic radius of the same element. same element.

WhyWhy? Generally, ? Generally, metals loose electrons metals loose electrons to achieve the octet. to achieve the octet. This creates a larger This creates a larger positive charge in the positive charge in the nucleus than the nucleus than the negative charge in the negative charge in the electron cloud, electron cloud, causing the electron causing the electron cloud to be drawn a cloud to be drawn a little closer to the little closer to the nucleus as an ion.nucleus as an ion.

Ionic Radius vs. Atomic Radius Ionic Radius vs. Atomic Radius cont.cont.

Non-metals - the atomic radius of a Non-metals - the atomic radius of a non-metal is generally smaller than the non-metal is generally smaller than the ionic radius of the same element. ionic radius of the same element.

WhyWhy? Generally, non-metals gain ? Generally, non-metals gain electrons to achieve the octet. This electrons to achieve the octet. This creates a larger negative charge in the creates a larger negative charge in the electron cloud than positive charge in electron cloud than positive charge in the nucleus, causing the electron cloud the nucleus, causing the electron cloud to 'puff out' a little bit as an ion. to 'puff out' a little bit as an ion. 

Ionic Radius vs. Atomic RadiusIonic Radius vs. Atomic Radius

Summary of Periodic TrendsSummary of Periodic TrendsATOMIC NUMBER INCREASES

ATOMIC RADIUS DECREASES

IONIZATION ENERGY INCREASES

ELECTRONEGATIVITY INCREASES

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