periodic table periods atoms in a period have the same number of energy levels

Periodic Table PeriodsPeriodic Table Periods

• Atoms in a period have the same number Atoms in a period have the same number of energy levels.of energy levels.

Periodic Table GroupsPeriodic Table Groups

Many groups have special names that Many groups have special names that describe their characteristics.describe their characteristics.

Atoms in a group have same number of Atoms in a group have same number of valence electrons so they behave valence electrons so they behave similarly.similarly.Roman numerals represent the Roman numerals represent the

number of valence electrons.number of valence electrons.

Terms to KnowTerms to Know

Cations refer to the elements that lose Cations refer to the elements that lose electrons and form a positive ion.electrons and form a positive ion.

Anions refer to the elements that gain Anions refer to the elements that gain electrons and form a negative ion.electrons and form a negative ion.

Alkali MetalsAlkali Metals

All form +1 cationsAll form +1 cationsVery reactive with waterVery reactive with waterHighly reactive in generalHighly reactive in general

Alkaline Earth MetalsAlkaline Earth Metals

All form +2 CationsAll form +2 CationsSomewhat reactive with waterSomewhat reactive with waterHighly reactive with acids.Highly reactive with acids.

HalogensHalogens

All form -1 AnionsAll form -1 AnionsAggressive OxidizersAggressive OxidizersUsed in Halogen bulbs.Used in Halogen bulbs.

Noble GasesNoble Gases

Non-reactiveNon-reactiveFulfilled Octet Rule—have 8 valence Fulfilled Octet Rule—have 8 valence

electrons in the outer most energy level electrons in the outer most energy level and considered stable.and considered stable.

Other GroupsOther GroupsGroup 13 (IIIA) – Boron FamilyGroup 13 (IIIA) – Boron Family

Form +3 CationsForm +3 CationsGroup 14 (IVA) – Carbon FamilyGroup 14 (IVA) – Carbon Family

Form Form ++ 4 Cations or Anions 4 Cations or AnionsGroup 15 (VA) – Nitrogen GroupGroup 15 (VA) – Nitrogen Group

Form -3 AnionsForm -3 AnionsGroup 16 (VIA) – Oxygen FamilyGroup 16 (VIA) – Oxygen Family

Form -2 AnionsForm -2 Anions

PeriodicityPeriodicity When elements are arranged in order of When elements are arranged in order of

increasing atomic number, there is a periodic increasing atomic number, there is a periodic repetition of their physical and chemical repetition of their physical and chemical properties.properties.

An important consequence is that the elements An important consequence is that the elements with similar chemical and physical properties with similar chemical and physical properties end up in the same column.end up in the same column.

Trends on the periodic table govern how Trends on the periodic table govern how elements behave chemically.elements behave chemically.

All elements are unique, but follow these All elements are unique, but follow these trends….generally.trends….generally.

Atomic Size/Atomic RadiusAtomic Size/Atomic Radius Atomic radius is ½ the distance between the

nuclei of identical atoms that are bonded together. Group Trend – size INCREASES as you move

down (added energy levels; electrons farther from nucleus).

Period Trend – size DECREASES as you move left to right (more protons and electrons pulling harder on one another).Due to increasing energy levels and shielding

by inner electrons. Inner electrons shield the outermost electrons from the nucleus.

Atomic Size Cont.Atomic Size Cont.

Which atom has the larger radius?Which atom has the larger radius?

Be or Ba

Ca or Br

Ba

Ca

ExamplesExamples

Ionic Size/Ionic RadiusIonic Size/Ionic Radius Ionic RadiusIonic Radius is the relative size of the most is the relative size of the most

common ion of an atom.common ion of an atom. Group TrendGroup Trend – INCREASE top to bottom due – INCREASE top to bottom due

to shielding.to shielding.Cations are always smaller than their neutral Cations are always smaller than their neutral

atomatomLoss of electrons increase attractionLoss of electrons increase attraction

Anions are always bigger than their neutral Anions are always bigger than their neutral atom.atom.Gain of electrons decrease attractionGain of electrons decrease attraction

Period TrendPeriod Trend – DECREASE left to right. – DECREASE left to right.

ElectronegativityElectronegativityElectronegativityElectronegativity is a measure of the ability is a measure of the ability

of an atom in a chemical compound to of an atom in a chemical compound to attract electrons when they are chemically attract electrons when they are chemically combined with atoms of another element.combined with atoms of another element.

Group TrendGroup Trend – DECREASE as you move – DECREASE as you move down due to increasing number of energy down due to increasing number of energy levels.levels.

Period TrendPeriod Trend – INCREASE from left to right – INCREASE from left to right right due to switch from cat ions to anions.right due to switch from cat ions to anions.Fluorine has an electronegativity of 4.0, Fluorine has an electronegativity of 4.0,

everything below and to the left is lower.everything below and to the left is lower.

ElectronegativityElectronegativity

ElectronegativityElectronegativity

Ionization EnergyIonization Energy Ionization EnergyIonization Energy is the energy required to is the energy required to

overcome the attraction of the protons and overcome the attraction of the protons and remove one electron from a neutral atom of an remove one electron from a neutral atom of an element .element .

The energy required to remove the 1The energy required to remove the 1stst outermost outermost electron is call the 1electron is call the 1stst ionization energy. And the ionization energy. And the energy for the 2energy for the 2ndnd outermost electron to be outermost electron to be removed is called 2removed is called 2ndnd ionization energy. ionization energy.

Atoms may have 2Atoms may have 2ndnd or 3 or 3rdrd ionization energies ionization energies depending on number of valence electrons and depending on number of valence electrons and adherence to octet rule.adherence to octet rule.

Ionization EnergyIonization Energy Group TrendGroup Trend – ionization energy DECREASES – ionization energy DECREASES

as you move down (electrons further from the as you move down (electrons further from the pull of the nucleus are easier to remove).pull of the nucleus are easier to remove).

Period TrendPeriod Trend – ionization energy INCREASES – ionization energy INCREASES as you move left to right (greater attraction of as you move left to right (greater attraction of the nucleus for electrons).the nucleus for electrons).

Ionization Energy Cont.Ionization Energy Cont.

Which atom has the higher 1st I.E.?Which atom has the higher 1st I.E.?

N or Bi

Ba or Ne

N

Ne

ExamplesExamples

Summary of Periodic TrendsSummary of Periodic Trends