Section 5-2:Section 5-2:Electron Configuration and Electron Configuration and

the Periodic Tablethe Periodic Table

Coach KelsoeCoach Kelsoe

ChemistryChemistry

Pages 138-149Pages 138-149

Section ObjectivesSection Objectives

Describe the relationship between electrons in Describe the relationship between electrons in sublevels and the length of each period of the sublevels and the length of each period of the periodic table.periodic table.

Locate and name the four blocks of the periodic Locate and name the four blocks of the periodic table, as well as explain the reason for these names.table, as well as explain the reason for these names.

Discuss the relationship between group Discuss the relationship between group configurations and group numbers.configurations and group numbers.

Describe the locations in the periodic table and the Describe the locations in the periodic table and the general properties of the alkali metals, the alkaline-general properties of the alkali metals, the alkaline-earth metals, the halogens, and the noble gases.earth metals, the halogens, and the noble gases.

Periods and Blocks of the Periodic Periods and Blocks of the Periodic TableTable

Remember that elements are arranged vertically in Remember that elements are arranged vertically in groups and horizontally in periods.groups and horizontally in periods.

Elements in the same group share chemical Elements in the same group share chemical properties.properties.

The length of each period is determined by the The length of each period is determined by the number of electrons that can occupy the sublevels number of electrons that can occupy the sublevels being filled in that period.being filled in that period.

Periods and Blocks of the Periodic Periods and Blocks of the Periodic TableTable

The first period consists of two elements The first period consists of two elements because the 1s sublevel can only 2 electrons.because the 1s sublevel can only 2 electrons.

In the second period, the 2s sublevel can hold In the second period, the 2s sublevel can hold two electrons and the 2p sublevel can hold 6, two electrons and the 2p sublevel can hold 6, so the second period has 8 elements.so the second period has 8 elements.

The same applies to the third period.The same applies to the third period. At the fourth period, the 4s sublevel can hold At the fourth period, the 4s sublevel can hold

2 electrons, the 3d sublevel can hold 10 2 electrons, the 3d sublevel can hold 10 electrons, and the 4p sublevel can hold 6.electrons, and the 4p sublevel can hold 6.

Periods and Blocks of the Periodic Periods and Blocks of the Periodic TableTable

The period of an element The period of an element can be determined from the can be determined from the element’s electron element’s electron configuration.configuration.

For example, arsenic (As) For example, arsenic (As) has the Noble Gas has the Noble Gas configuration [Ar]3dconfiguration [Ar]3d10104s4s224p4p33. . The 4 in the 4pThe 4 in the 4p33 indicates indicates that the highest occupied that the highest occupied energy level is the fourth energy level is the fourth energy level.energy level.

Periods and Blocks of the Periodic Periods and Blocks of the Periodic TableTable

Based on the electron Based on the electron configurations of the configurations of the elements, the periodic table elements, the periodic table can be divided into four can be divided into four blocks, the blocks, the ss, , pp, , dd, and , and ff blocks.blocks.

The name of each block is The name of each block is determined by whether an determined by whether an ss, , pp, , dd, or , or ff sublevel is being sublevel is being filled in successive elements.filled in successive elements.

Important NoticeImportant Notice

It is important to It is important to realize that not all realize that not all periodic tables have periodic tables have the information the information arranged in the same arranged in the same way.way.

Atomic numbers will Atomic numbers will nevernever have a decimal have a decimal and will and will alwaysalways be in be in numerical order.numerical order.

The The ss-Block Elements: Group 1 & 2-Block Elements: Group 1 & 2

The elements of the s block are chemically The elements of the s block are chemically reactive metals.reactive metals.

Group 1 elements are extremely reactive Group 1 elements are extremely reactive because of how easily they lose their electron.because of how easily they lose their electron.

Using Using nn for the number of the highest for the number of the highest occupied energy level, the outer, or group, occupied energy level, the outer, or group, configurations of the Group 1 and 2 elements configurations of the Group 1 and 2 elements are written as are written as nsns11 and and nsns22 respectively. respectively.

Alkali MetalsAlkali Metals

The elements of Group 1 of The elements of Group 1 of the periodic table (lithium, the periodic table (lithium, sodium, potassium, sodium, potassium, rubidium, cesium, and rubidium, cesium, and francium) are known as the francium) are known as the alkali metalsalkali metals..

In pure state, all have a In pure state, all have a silvery appearance and are silvery appearance and are soft enough to be cut with a soft enough to be cut with a knife.knife.

Alkali MetalsAlkali Metals

Properties of alkali metals:Properties of alkali metals: Silvery appearanceSilvery appearance Soft in textureSoft in texture Not found in nature as free Not found in nature as free

elements because they elements because they combine with other elements.combine with other elements.

Combine vigorously with Combine vigorously with most nonmetalsmost nonmetals

React strongly with water to React strongly with water to produce Hproduce H22 gas and alkalis. gas and alkalis.

Alkali-Earth MetalsAlkali-Earth Metals

The elements of Group 2 of The elements of Group 2 of the periodic table (beryllium, the periodic table (beryllium, magnesium, calcium, magnesium, calcium, strontium, barium, & radium) strontium, barium, & radium) are called the are called the alkali-earth alkali-earth metalsmetals..

Atoms of alkali-earth metals Atoms of alkali-earth metals contain a pair of electrons in contain a pair of electrons in their outermost their outermost ss sublevel. sublevel.

Alkali-Earth MetalsAlkali-Earth Metals

The Group 2 metals are The Group 2 metals are harder, denser, and harder, denser, and stronger than the alkali stronger than the alkali metals.metals.

They also have higher They also have higher melting points.melting points.

They are less reactive than They are less reactive than alkali metals, but they too alkali metals, but they too are too reactive to be found are too reactive to be found free in nature.free in nature.

Hydrogen and HeliumHydrogen and Helium

Hydrogen and helium are special Hydrogen and helium are special cases in the periodic table.cases in the periodic table.

Hydrogen has an electron Hydrogen has an electron configuration of 1configuration of 1ss11, but it does , but it does not share the same properties as not share the same properties as the elements of Group 1.the elements of Group 1.

Helium is also different from the Helium is also different from the Group 18 elements. It is very Group 18 elements. It is very stable because its outermost stable because its outermost energy level is filled by 2 energy level is filled by 2 electrons.electrons.

Sample ProblemSample Problem

Without looking at the periodic table, give the Without looking at the periodic table, give the group, period, and block in which the element group, period, and block in which the element with the electron configuration [Xe]6with the electron configuration [Xe]6ss22 is is located.located. Group 2, Period 6, Block Group 2, Period 6, Block ss

Without looking at the periodic table, write the Without looking at the periodic table, write the electron configuration for the Group 1 element electron configuration for the Group 1 element in the 3in the 3rdrd period. Is this element likely to be period. Is this element likely to be more active or less active than the previous?more active or less active than the previous? 11ss2222ss2222pp6633ss11; it is likely to be more reactive; it is likely to be more reactive

The d-Block Elements: Groups 3-12The d-Block Elements: Groups 3-12

For energy level For energy level nn, there , there are are nn possible sublevels, so possible sublevels, so we don’t see the we don’t see the dd sublevel sublevel until the 3until the 3rdrd energy level. energy level.

Remember that the 3Remember that the 3dd sublevel is higher in energy sublevel is higher in energy than the 4than the 4ss, so they will fill , so they will fill up in order of 4up in order of 4ss33dd..

The The dd sublevel is made up sublevel is made up of 5 orbitals that can hold a of 5 orbitals that can hold a total of 10 electrons.total of 10 electrons.

The d-Block Elements: Groups 3-12The d-Block Elements: Groups 3-12

The group configuration for The group configuration for Group 3 is (Group 3 is (nn-1)-1)dd11nsns22..

The group configuration for The group configuration for Group 12 is (Group 12 is (nn-1)-1)dd1010nsns22..

There are a few exceptions. There are a few exceptions. For elements like For elements like Palladium and Platinum, Palladium and Platinum, those lower energy levels those lower energy levels do not fill up first.do not fill up first.

The d-Block Elements: Groups 3-12The d-Block Elements: Groups 3-12

The The dd-block elements are -block elements are metals with typical metallic metals with typical metallic properties and are often properties and are often referred to as referred to as transition transition elementselements..

They are good conductors They are good conductors of electricity, have a high of electricity, have a high luster, and are less reactive luster, and are less reactive than alkali and alkali-earth than alkali and alkali-earth metals.metals.

Essentials for LifeEssentials for Life

These elements are essential These elements are essential for life and make up over for life and make up over 96% of the human body.96% of the human body. CarbonCarbon HydrogenHydrogen OxygenOxygen PhosphorusPhosphorus SulfurSulfur NitrogenNitrogen

Sample ProblemSample Problem

An element has the electron configuration An element has the electron configuration [Ar]3[Ar]3dd8844ss22. Without looking at the periodic . Without looking at the periodic table, identify the period, block, and group in table, identify the period, block, and group in which this element is located.which this element is located. 44thth Period – indicated by the highest occupied Period – indicated by the highest occupied

energy levelenergy level dd-block – indicated by the (-block – indicated by the (nn-1)-1)dd1-101-10nsns0-20-2 notation notation Group 10 – indicated by the total number of Group 10 – indicated by the total number of

electrons in the outer energy level.electrons in the outer energy level.

The The pp-Block Elements: Groups 13-18-Block Elements: Groups 13-18

The The pp-block elements -block elements consist of all the elements consist of all the elements of Groups 13-18 except of Groups 13-18 except Helium.Helium.

Electrons add to a Electrons add to a pp sublevel only after the s sublevel only after the s sublevel in the same sublevel in the same energy level is filled.energy level is filled.

Atoms of all Atoms of all pp-block -block elements contain two elements contain two electrons in the electrons in the nsns sublevel. sublevel.

The The pp-Block Elements: Groups 13-18-Block Elements: Groups 13-18

The The pp-block elements -block elements and the and the ss-block -block elements are called the elements are called the main-group elementsmain-group elements..

For Group 13, the group For Group 13, the group configuration is configuration is nsns22npnp11..

For Group 18, the group For Group 18, the group configuration is the configuration is the nsns22npnp66..

The The pp-Block Elements: Groups 13-18-Block Elements: Groups 13-18

For atoms of For atoms of pp-block -block elements, the total number elements, the total number of electrons in the highest of electrons in the highest occupied level is equal to occupied level is equal to the group number minus 10.the group number minus 10.

In the In the pp-block elements, -block elements, there are metals, metalloids, there are metals, metalloids, and nonmetals.and nonmetals.

The HalogensThe Halogens

The elements of Group 17 The elements of Group 17 (fluorine, chlorine, bromine, (fluorine, chlorine, bromine, iodine, and astatine) are known iodine, and astatine) are known as the as the halogenshalogens..

The halogens are the most The halogens are the most reactive nonmetals.reactive nonmetals.

They react with most metals to They react with most metals to form salts.form salts.

For all atoms, reactivity is based For all atoms, reactivity is based on the presence of electrons in on the presence of electrons in the outermost energy level.the outermost energy level.

The HalogensThe Halogens

Characteristics of some of Characteristics of some of the halogens:the halogens: Fluorine and chlorine are Fluorine and chlorine are

gases at room temperature.gases at room temperature. Bromine is a reddish liquid.Bromine is a reddish liquid. Iodine is a dark purple solid.Iodine is a dark purple solid. Astatine is a synthetic Astatine is a synthetic

element prepared in only very element prepared in only very small quantities.small quantities.

MetalloidsMetalloids

MetalloidsMetalloids are are semiconducting elements semiconducting elements that are mostly brittle solids that are mostly brittle solids with some properties of with some properties of metals and some of metals and some of nonmetals.nonmetals.

The metalloids have The metalloids have electrical conductivity electrical conductivity intermediate between that intermediate between that of metals and nonmetals.of metals and nonmetals.

Properties of Properties of pp-Block Elements-Block Elements

The The pp-block elements are -block elements are generally harder and generally harder and denser than the denser than the ss-block -block elements, but softer and elements, but softer and less dense than the less dense than the dd--block elements.block elements.

With the exception of With the exception of bismuth, these metals are bismuth, these metals are sufficiently reactive to be sufficiently reactive to be found in nature only in the found in nature only in the form of compounds.form of compounds.

Sample ProblemSample Problem

Without looking at the periodic table, write the Without looking at the periodic table, write the outer electron configuration for the Group 14 outer electron configuration for the Group 14 element in the second period. Then name the element in the second period. Then name the element.element. It is in the It is in the pp-block because its group is higher -block because its group is higher

than 12than 12 The total number of electrons in the highest The total number of electrons in the highest

occupied s and p sublevels is equal to the group occupied s and p sublevels is equal to the group number minus 10, so 14-10=4number minus 10, so 14-10=4

Being in the 2Being in the 2ndnd period, it must be 2 period, it must be 2ss2222pp22..

The The ff-Block Elements: Lanthanides -Block Elements: Lanthanides and Actinidesand Actinides

The The ff-block elements are wedged between -block elements are wedged between Groups 3 and 4 in the 6Groups 3 and 4 in the 6thth and 7 and 7thth periods. periods.

With seven 4With seven 4ff orbitals to be filled with two orbitals to be filled with two electrons each, there are a total of 14 electrons each, there are a total of 14 ff-block -block elements between lanthanum and hafnium.elements between lanthanum and hafnium.

There are also 14 There are also 14 ff-block elements between -block elements between Actinium and Rutherfordium.Actinium and Rutherfordium.