Chemical Periodicity and Ionic Formation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Electron plays the most significant role in determine physical and chemical properties of an element.

Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms.

These changes are chemical: iron rusting (iron oxide forms) gasoline burning (water vapor and carbon dioxide form) eggs cooking (fluid protein molecules uncoil and crosslink to form a network) bread rising (yeast converts carbohydrates into carbon dioxide gas) milk souring (sour-tasting lactic acid is produced) suntanning (vitamin D and melanin is produced)

Physical change rearranges molecules but doesn't affect their internal structures.

Some examples of physical change are: whipping egg whites (air is forced into the fluid, but no new substance is produced) magnetizing a compass needle (there is realignment of groups ("domains") of iron atoms, but no real change within the iron atoms themselves). boiling water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H 2 O.) dissolving sugar in water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.) dicing potatoes (cutting usually separates molecules without changing them.)

Trends in Atomic Size: As you move down a group, they increase

There are more energy shells added as one moves down a group There are more electrons located further and further away from the nucleus

As you move across the period from left to right, they decrease in size The electrons are all on the same energy shell (period)

The effect of the increasing positive nuclear charge, because you are adding more protons, on the outermost electrons causes this positive nucleus to pull those negative electrons closer to the nucleus

Get your book, get out a piece of paper, put your name on it- you will turn it into me at the END of notes Page: 399 Draw 8 boxes representing period 2 Draw the atomic radius of period 2 (see chart) Show the decrease of the atoms as your progress across the period Draw 6 boxes representing Group 1A Draw the atomic radius increase of Group 1A Show the INCREASE of the atomic radius as you move down a group

Trends in Ionization Energy: When an atom gains or loses an electron it becomes an ion…

The Tale of Two Atoms…. I am so hungry, I need to find some electrons …. Ugh..I am so full, I ate 1 too many electrons

What do you do if you are a sodium (Na) atom? You have 11 electrons, one too many to be happy & you are unstable.

Oh…what to do?!?!?! You need to find another element or atom who will take that electron away from you. I wish I had some friends..

Bring in chlorine (Cl). Chlorine (Cl) will take that electron away and leave you with 10 electrons. I hear you got some stuff I need…. I wonder if he can help me

You are a happy atom. (& so is Cl) You are also now an ion and missing 1 electron. +1

Cations- the positive ones! atoms that have donated an electron 1st examine the electron arrangement of the atom. The atomic # is 11, therefore, there are 11 e- and 11p+ on the neutral sodium atom.

Na has 1 e in its outer level. The nearest Noble gas is neon (Ne) with 8 electrons in the outer energy level. Therefore, this e is lost so that there are now 8 e in the outer energy level of the Sodium, and the octet rule is satisfied. Na 11e 1 e Ne 10e

The charges of Cations Group 1- donates 1 e - +1 charge Group 2- donates 2 e - +2 charge Group 3- donates 3 e - +3 charge Let’s see what it looks like ……

Sodium Na Na 11e 1 e Ne 10e

Magnesium (Mg) Mg 12e 2 e Ne 10e

Aluminum Al 13e 3 e Ne 10e

K K: 19 p+19p+ 19e- donates 1 e 18e- 0 **new charge** 1+ All of group 1A donates 1 e All of group 1A has a 1+ charge Ar 18

Ca K: 20 p+20p+ 20 e- donates 2 e 18e- 0 **new charge** 2+ All of group 2A donates 2 electrons All of Group 2A has a 2+ charge Ar 18

Ga K: 21 p+21p+ 21e- donates 3 e 18e- 0 **new charge** 3+ All of group 3A donates 3 e All of group 3A has a 3+ charge Ar 18

A Hard One: Find the # of electrons for Cu +2, So, if Cu is +2, then it has donated 2 e That means that we subtract 2 e out of the original total 29-2=27 Cu: 29 p+29p+ 29 e- donates 2 e 27e- 0 **new charge** 2+ Therefore Cu +2, has 27 e

Cu +3, So, if Cu is +3, then it has donated 3 e That means that we subtract 3 e out of the original totals 29-3=26 Cu: 29 p+29p+ 29 e- donates 3 e 26e- 0 **new charge** 3+ Therefore Cu +3, has 26 e

Fe +2, So, if Fe is +2, then it has donated 2 e That means that we subtract 2 e out of the original totals 26-2=24 Fe: 26 p+26p+ 26 e- donates 2 e 24e- 0 **new charge** 2+ Therefore Fe +2, has 24 e

Fe +3 So, if Fe is +3, then it has donated 3 e That means that we subtract 3 e out of the original totals 26-3=23 Fe: 26 p+26p+ 26 e- donates 3 e 23e- 0 **new charge** 3+ Therefore Fe +3, has 23 e

Anions: The Negative Ones atoms that have gained/ accepted electrons. Having more (-) electrons than (+) protons Group 7- accepts 1 e -1 charge Group 6- accepts 2 e -2 charge Group 5- accepts 3 e -3 charge

Fluoride 9 +p 9 –e 0 charge 9 +p 10-e -1 charge Now, it has 10 e like Neon!

N N: 7 p+7p+ 7 e- accepts 3 e 10e- 0 **new charge** 3- All of group 5A accepts 3 e All of group 5A has a 3- charge Ne 10e

o O: 8 p+8p+ 8 e- accepts 2 e 10e- 0 **new charge** 2- All of group 6A accepts 2 e All of group 6A has a 2- charge Ne 10e

Cl O: 17 p+17p+ 17 e- accepts 1 e 18e- 0 **new charge** 1- All of group 7A accepts 1 e All of group 6A has a 1- charge Ar 18

Te Te: 52 p e- accepts 2 e 54e- 0 **new charge** 2- Remember…all elements in a group have similar properties…so…. All of group 6A accepts 2 e All of group 6A has a 2- charge Xe 54

SUMMARY PRINCIPLE OF IONIC COMPOUNDS An ionic compound is formed by the complete transfer of e from a metal to a nonmetal and the resulting ions have achieved an octet. The protons do not change. Metal atoms in Groups 1-3 donate electrons to non-metals Non-metals gain or accept 1-4 electrons to complete an octet outer valence shell. Positive & Negative: + Protons are attracted to - electrons…just like in a magnet….

Octet Rule: Elemental atoms generally lose, gain, or share electrons with other atoms in order to achieve the same electron structure as the nearest noble gas with 8 e in the outer level. The application of the Octet Rule allows you to predict chemical reactions & formulas.

Most things we have done so far in this course, revolve around the octet rule… Lewis Dot Structures

And the stuff we will be doing in this course Chemical Reactions (Bonding)

Ionization energy Energy required to overcome the attraction of the nuclear charge and remove an electron from a gaseous state. Remove 1 electron creates a positive cation with a +1 charge

Energy required to remove the 1 st outermost electron is called the first ionization energy

To remove the outermost electron from the +1 ion requires 2 nd ionization energy…and so on

1 st ionization energy decreases as you move down a group because the size of the atom increases and its easier to lose the outermost electron of say Cs when it is so far away from the nucleus.

1 st ionization energy increases from left to right because the nuclear charge increases and there is greater attraction or reluctance to leave the positive nucleus.

Get your book, get out the same piece of paper, you will turn it into me at the END of notes Page: Draw 8 boxes representing period 2 Draw the 1 st ionization energy of period 2 (see chart) Show the increase of the energy as your progress across the period Draw 6 boxes representing Group 1A Draw the 1 st ionization energy decrease of Group 1A Show the decrease of the atomic radius as you move down a group

Trends in Ionic Size: Atoms of metallic elements have LOW ionization energy ( form positive ions easily) Nonmetallic elements form negative ions readily

Cations are ALWAYS smaller than neutral atoms because they LOSE an electron causing the negative electrons to be less than the positive nucleus and therefore pulled in tighter

Anions are always LARGER than the neutral atoms because they gain electrons and when there are more electrons than protons, the attraction is not as great.

Groups 1A-3A: Left to right- decrease in positive ions Groups 5A-7A: Left to right- decrease in negative ions Increase as you move down the groups

Trends in Electronegativity: Tendency for the atoms to attract electrons they are chemically combined with “Flo is a Ho”

Noble gases do NOT have electronegativity because they very rarely react with anything Groups: decrease Periods left to Right: increase

Cs= least electronegative F= most reactive Electronegativity helps determine what type of bonding will occur.