chapter 14 chemical periodicity. objective a chapter 14 is a very short chapter. we also already...

Chapter 14Chapter 14Chemical PeriodicityChemical Periodicity

Objective AObjective A

Chapter 14 is a very short Chapter 14 is a very short chapter. We also already know chapter. We also already know some of what is in this chapter.some of what is in this chapter.

The Periodic Table groups The Periodic Table groups elements according to their elements according to their properties.properties. Look at the first group. It has H and Li and Na, etc.Look at the first group. It has H and Li and Na, etc. All of these elements behave in the same ways. All of these elements behave in the same ways. If you know the properties of Li and Na, you can make If you know the properties of Li and Na, you can make

a very good inference that K and Cs will behave the a very good inference that K and Cs will behave the same way.same way.

Objective AObjective Ahttp://www.rsc.org/chemsoc/visualelements/Pages/data/intro_groupi_data.htmlhttp://www.rsc.org/chemsoc/visualelements/Pages/data/intro_groupi_data.html

You can only say that about elements in the same You can only say that about elements in the same group (column, going up and down)group (column, going up and down)

Elements in the same period can have different Elements in the same period can have different properties, so you can’t make the assumption that Na properties, so you can’t make the assumption that Na will behave like Mg or Mg will behave like Al.will behave like Mg or Mg will behave like Al.

We can use the electron configuration to make We can use the electron configuration to make assumptions about the element. Elements in the same assumptions about the element. Elements in the same group will have the same “ending” to their electron group will have the same “ending” to their electron configuration.configuration.Li [He]2s1 Na [Ne]3s1

K [Ar]4s1 Rb [Kr]5s1

Cs [Xe]6s1 Fr [Rn]7s1

Objective BObjective Bhttp://www.rsc.org/chemsoc/visualelements/Pages/data/intro_groupviii_data.htmlhttp://www.rsc.org/chemsoc/visualelements/Pages/data/intro_groupviii_data.html

Alkali metals all have 1 electron in their highest occupied energy Alkali metals all have 1 electron in their highest occupied energy level.level.

Noble gases all have 8 electrons in their highest occupied energy Noble gases all have 8 electrons in their highest occupied energy level. That’s not true for Helium, but remember that Helium only level. That’s not true for Helium, but remember that Helium only has the 1s orbital (so when it has 2 electrons, it’s highest has the 1s orbital (so when it has 2 electrons, it’s highest occupied energy level is full).occupied energy level is full).

We call the electrons in the highest occupied energy level the We call the electrons in the highest occupied energy level the “valence electrons.”“valence electrons.”

He 1s2 Ne [He]2s22p6

Ar [Ne]3s23p6 Kr [Ar]3d104s24p6

Xe [Kr]4d105s25p6 Rn [Xe]4f145d106s26p6

Shorthand configurations…we’ll learn about those in just a sec…

Objective BObjective Bhttp://www.rsc.org/chemsoc/visualelements/PAGES/data/intro_groupvii_data.htmlhttp://www.rsc.org/chemsoc/visualelements/PAGES/data/intro_groupvii_data.html

Notice that the halogens all have an Notice that the halogens all have an ending configuration of nsending configuration of ns22npnp55. That . That means they have 7 valence electrons.means they have 7 valence electrons.

Let’s also look at the transition metals. Let’s also look at the transition metals. We’ll only look at the first row, called the We’ll only look at the first row, called the first transition series of elements.first transition series of elements.

F [He]2s22p5 Cl [Ne]3s23p5

Br [Ar]3d104s2 4p5 I [Kr]4d105s2 5p5

At [Xe]4f14 5d106s2 6p5

Objective BObjective B

All of the transition metals have 2 valence All of the transition metals have 2 valence electrons, with 2 exceptions.electrons, with 2 exceptions.

Transition metals are where the d orbitals Transition metals are where the d orbitals are being filled up. Here are the electron are being filled up. Here are the electron configurations for all of them.configurations for all of them.


Notice that Cr and Cu are Notice that Cr and Cu are “exceptions.”“exceptions.”

They both have 1 valence They both have 1 valence electron. They do this because electron. They do this because in the case of Cr, moving an in the case of Cr, moving an electron from the 4s level to electron from the 4s level to the 3d level gives us a half full the 3d level gives us a half full set of d orbitals.set of d orbitals.


That’s more stable than if Cr That’s more stable than if Cr would have followed the pattern, would have followed the pattern, and ended with “4sand ended with “4s223d3d44””

Similarly, Cu has 1 electron in Similarly, Cu has 1 electron in the 4s energy level and 10 in the the 4s energy level and 10 in the 3d level, because having a full 3d level, because having a full set of d electrons is also more set of d electrons is also more stable.stable.


We won’t do much in this class We won’t do much in this class with the second transition series with the second transition series or the third.or the third.

We will talk about some of those We will talk about some of those elements, but most of the elements, but most of the patterns for the first transition patterns for the first transition series will hold true for the series will hold true for the others.others.


The “inner transition metals” are the The “inner transition metals” are the lanthanide and actinide series. lanthanide and actinide series.

That’s where the f electrons are filled up. That’s where the f electrons are filled up.

That’s about all I’m going to say about That’s about all I’m going to say about that, except that Glenn Seaborg was the that, except that Glenn Seaborg was the first to propose the existence of the first to propose the existence of the actinides.actinides.

He called it the Actinide Hypothesis, and He called it the Actinide Hypothesis, and many scientists felt that he was wrong. many scientists felt that he was wrong. However, he was proven to be correct.However, he was proven to be correct.


Shorthand configurations are a Shorthand configurations are a useful tool.useful tool.

As you can see, when you get a As you can see, when you get a lot of electrons, the configuration lot of electrons, the configuration can get pretty long.can get pretty long.

Let’s look at an example for Y, Let’s look at an example for Y, Z=39Z=39


The electron configuration for The electron configuration for yttrium isyttrium is

1s1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p665s5s224d4d11

To do a shorthand configuration, To do a shorthand configuration, we use the noble gas preceding we use the noble gas preceding the element and we put that in the element and we put that in brackets.brackets.



The noble gas that precedes Y is The noble gas that precedes Y is Kr.Kr.

Kr electron configuration is Kr electron configuration is 1s1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p66, which , which we represent as [Kr].we represent as [Kr].



I can replace the underlined part I can replace the underlined part with [Kr], leaving me with a with [Kr], leaving me with a shorthand configuration ofshorthand configuration of

[Kr]5s[Kr]5s224d4d11


Do a shorthand configuration for Do a shorthand configuration for

FeFe

BrBr

Hg don’t forget that after 6s comes 4f and Hg don’t forget that after 6s comes 4f and 5d!5d!


Do a shorthand configuration for Do a shorthand configuration for

Fe = [Ar]4sFe = [Ar]4s223d3d66

Br = [Ar]4sBr = [Ar]4s223d3d10104p4p55

Hg = [Xe]6sHg = [Xe]6s224f4f14145d5d1010

Objective CObjective C

The periodic table allows you to predict The periodic table allows you to predict trends in certain properties.trends in certain properties.

Atomic radius is one of those properties. Atomic radius is one of those properties.

Atomic radius is the size of the atom. Atomic radius is the size of the atom. It’s defined as ½ the distance between It’s defined as ½ the distance between two nuclei which are bonded together.two nuclei which are bonded together.


Ionic radius is another propertyIonic radius is another property

It is the size of an ion. Ionic radius is fairly It is the size of an ion. Ionic radius is fairly similar to atomic radius.similar to atomic radius.

A positive ion is also called a CATION.A positive ion is also called a CATION.

A negative ion is also called an ANION.A negative ion is also called an ANION.


A cation is always smaller than the A cation is always smaller than the atomatom it is formed from. it is formed from.

An An anionanion is always larger is always larger than the than the atomatom it is formed from. it is formed from.

Since cations lose electrons to form positive ions Since cations lose electrons to form positive ions and anions gain electrons to form negative ions, and anions gain electrons to form negative ions, that should make sense.that should make sense.


Ionization energy is the amount Ionization energy is the amount of energy required to remove an of energy required to remove an electron from a gaseous atom.electron from a gaseous atom.

The energy required to remove The energy required to remove the first electron is called the the first electron is called the FIRST IONIZATION ENERGY.FIRST IONIZATION ENERGY.


The energy required to remove the second The energy required to remove the second electron is the second ionization energy.electron is the second ionization energy.

Metals always have LOWER ionization Metals always have LOWER ionization energies than nonmetals.energies than nonmetals.

That is because metals tend to lose electrons That is because metals tend to lose electrons and nonmetals tend to gain them.and nonmetals tend to gain them.


It is easier to remove a valence electron (an It is easier to remove a valence electron (an electron in the highest energy level) than an electron in the highest energy level) than an “inner core” electron.“inner core” electron.

The inner core electrons are the electrons in The inner core electrons are the electrons in the lower energy levels. For example, sodium the lower energy levels. For example, sodium has 1 valence electron in the 3has 1 valence electron in the 3rdrd energy level. energy level. Sodium has 8 electrons in the 2 Sodium has 8 electrons in the 2ndnd energy energy level and 2 in the 1level and 2 in the 1stst. The 10 electrons in the . The 10 electrons in the 11stst and 2 and 2ndnd levels are called “inner core” levels are called “inner core” electrons.electrons.


Electronegativity is the tendency of an Electronegativity is the tendency of an element to attract electrons to itself when element to attract electrons to itself when they are bonded to another element.they are bonded to another element.

Nonmetals have a very high electronegativity Nonmetals have a very high electronegativity and metals have a very low electronegativity.and metals have a very low electronegativity.


Electronegativity is measured on a scale from Electronegativity is measured on a scale from 0.0 to 4.0. 0.0 to 4.0.

By definition, F is the most electronegative By definition, F is the most electronegative element at 4.0.element at 4.0.


Now the trends…..Now the trends…..

Atomic radius increases as you go down a Atomic radius increases as you go down a group.group.

Atomic radius decreases as you go from left Atomic radius decreases as you go from left to right across a period.to right across a period.



Ionic radius increases as you go down a group.Ionic radius increases as you go down a group.

Ionic radius decreases as you go from left to Ionic radius decreases as you go from left to right across a period.right across a period.

However, there is a big jump in size between However, there is a big jump in size between groups 4A and 5A (this is where you switch groups 4A and 5A (this is where you switch from cations to anions).from cations to anions).



Ionization energy decreases as you go down a Ionization energy decreases as you go down a group.group.

Ionization energy increases as you go from Ionization energy increases as you go from left to right across a period.left to right across a period.



Electronegativity decreases as you go down a Electronegativity decreases as you go down a group.group.

Electronegativity increases as you go from Electronegativity increases as you go from left to right across a period.left to right across a period.


If it helps…put arrow on If it helps…put arrow on one of your periodic tables one of your periodic tables showing the trends.showing the trends.

The EndThe End

chapter 14 chemical periodicity. objective a chapter 14 is a very short chapter. we also already...

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