The Periodic TableBeyond protons, neutrons, and

electrons

The Modern Periodic Table

The original PT was arranged by mass By Dmitri Mendeleev and J Lothar Meyer in

1869 Mendeleev predicted the existence of unknown

elements (which turned out to be Ge, Sc, and Ga), and predicted their properties from the patterns he saw

Mendeleev corrected the assumed atomic masses for elements (In, Be, U)

These are reasons why he is credited with the first periodic table and is dubbed “The Father of the Modern Periodic Table” over Meyer

Ekasilicon

Changes….

Henry Mosley changed the table to be organized by atomic number (Z) instead; it then more closely followed trends/ patterns

e- configuration and the PT

PT also shows trends in electron configuration Groups are based upon electron configuration

Alkali metals are #s1 (# is period) Alkaline earth metals are #s2 (# is period) Halogens #p5 (# is period) Noble gases #p6 (# is period) Transition metals d block (# is period -1) Inner transition metals are f block (# is period -2)

Blocks and l* *

* orbital shapeThe blocks you already know correspond to the orbital of the last (outermost) e- , or valence e-s occupied

Effective Nuclear Charge

Given by the formula

Zeff = Z – S

Where Z is the number of protons in the nucleus and S is the average number of electrons between the nucleus and the electron in question

The effective nuclear charge experienced by the outer electrons is determined primarily by the difference between the charge on the nucleus and the charge of the core electrons.

Effective Nuclear Charge

What is the effective nuclear charge an outer electron of Na experiences?

What is the effective nuclear charge an outer electron of Mg experiences?

K?

Why is this important?

The effective nuclear charge experienced by outer electrons increases as we move from element to element across any row.

Why? The number of core electrons remains constant, while the nuclear charge increases.

The effective nuclear charge experienced by outer shell electrons increases only slightly as we move down a family. Because of the slight change, this trend is far less important.

Patterns (Periods) and the PT

We see patterns for many things, including Atomic number *(not a periodic pattern, but a pattern)

Electron configuration Atomic radii Ionization energy Electron affinity Electronegativity Activity Density

The Periodic Law

Mendeleev says "The properties of the elements are a periodic function of their atomic masses"

We now say: “When atoms are arranged by increasing atomic number, the physical and chemical properties show a (repeating) pattern”

Periodic…

Summed up: Properties of elements are periodic functions of their atomic numbers.

Hence, we call the table of elements the PERIODIC table (go figure)

Octet Rule

“Atoms gain, lose, or share electrons in order to create a full outer shell” This is typically going to be eight electrons

H and He are exceptions; wanting to fill the 1s orbital H gains an electron to become H- , with the same electron

configuration as He H may want to go to no electrons, which is considered

“full” even though it is empty H+ and He+2 would have no electrons left

The law can be used to predict several properties

Atomic Radii

•Half the distance between adjacent nuclei

•½ (2R)= atomic radius

Atomic Radii

The radius increases as you go down a group This is because n increases

The radius decreases as you go across a period(Yes, this is counterintuitive) Due to the fact that you add e- as you add p+, so the

nucleus is more positively charged, and each electron has the same negative charge

Results in each electron being more attracted to the (increasingly) more positive nucleus, and being pulled in closer

Sort of like making a magnet more powerful- it will decrease the distance where it will pull objects towards it

Radii (2)

* The radii for the Noble gases is INCORRECT- they should be smaller!

Ionic Radii Cations (+)

Smaller than the neutral atom The electrons have less repulsion, and pull in

closer to the nucleus

Anions (-)

Larger than the neutral atom More electrons = more repulsion = larger

electron cloud

Ionization Energy (Heretofore called IE)

IE is the amount of energy needed to remove an electron from an atom

(specifically, an isolated atom of the element in the gas phase)

Measure in kJ/ molAl(g)Al(g)

+ + e- I1 = 580 kJ/mol

Al(g)

+ Al(g)

+2 + e- I2 = 1815 kJ/mol

IE, continued

The Energy needed to remove the first electron from an element is the 1st IE

The Energy needed to remove the second electron is known as the 2nd IE

Successive IE

There are also 3rd, 4th, 5th , and so on IEs (which are successive IEs), until you can’t pull any more off

It takes more energy to remove successive electrons than to remove the first Due to the fact that there are then more protons than

electrons, and the stronger positive charge will then act on the remaining electrons to hold them to the atom

(Remember that the charge on the nucleus increases while the charge on each electron remains the same, causing more pull by the nucleus on each individual electron)

Why IE?

Since electrons (-) want to hang around the atom (due to the + protons in the nucleus pulling on them), it takes energy to remove electrons

In general The smaller that atom, the more energy it takes to remove

an electron Because the electron is closer to the nucleus than in a

larger atom The fewer electrons that atom possess, the harder it is to

remove an electron Because it will hang on to them tighter as they are closer

to the + charged nucleus; also, the less repulsion between electrons

1st IE

Stuff to keep in mind…

Remember (from coming up with the abbreviated electron configurations) that: Inner core electrons are those electrons from

previous Noble Gas Valence electrons are the electrons that are on

the exterior of an atom These are the electrons that are responsible for

the behavior (properties) of the element

Successive IEs

Are higher than the first Due to the fact that there is going to be more protons

than electrons at that point, resulting in a stronger attraction on the remaining electrons than there was in the first place

Basically increasingly larger jumps as each electron is removed

One jump is usually much larger than the others, because once the inner core configuration is reached, electrons are removed from the inner core, taking a lot more energy

Much bigger difference between positive nucleus and negative electron

Successive IEs

I1 I2 I3 I4 I5 I6 I7

Na 495 4560

Mg 735 1445 7730

Al 580 1815 2740 11600

Si 780 1575 3220 4350 16100

P 1060 1890 2905 4950 6270 21200

Si 1005 2260 3375 4565 6950 8490 27000

Cl 1255 2295 3850 5160 6560 9360 11000

Ar 1527 2665 3945 5770 7230 8780 12000

IE and the PT

Electron Affinity (EA)

The energy change associated with the addition of an electron to a gaseous atom

Negative values mean that energy is released when adding an e- more negative means more E released when adding

an electron Wants an electron more than something with a more

positive value Positive values mean that energy needs to be added

to add an e- More positive means more E needed to add the

electron Does not want an added electron; takes E to do it

The trend for EA is?

EA becomes more positive moving down the PT

EA becomes more negative from left to right Farther from the nucleus

There are several exceptions to this The smaller the atom, the more e--e- repulsion

when adding electrons

EA trends

Electronegativity (Eneg)

The ability of an atom to attract electrons in a bond Some atoms share electrons easily, others are

electron hogs The ability to share is rated (usually) from 0 to

4 Elements with 0 Eneg share easily Elements with a high (close to 4) Eneg don’t

share e- well

Electronegativity Trends

If it normally goes +, it has a low Eneg If it normally goes -, it is has a high Eneg

The smaller it is, the higher the Eneg The larger it is, the lower the Eneg

Noble gases, which normally take no charge, we say have no Eneg values

Electronegativity Trends

Metallic character Metallic character is acting like a metal (conductive, shiny,

malleable,etc) All elements possess from very low to very high metallic

character. The scale is from Fr to F. Fr has the most metallic character and F has the least.

In groups,  metallic character increases with atomic number because each successive element gets closest to Fr.

In periods,  metallic character decreases when atomic number increases because each successive element gets closest to F.

Reactivity

The nature (metal, non-metal, semi-metal) makes a difference in how an element’s chemical reactivity

The trends are characterized by their nature

Metals reactivity trend

In groups, reactivity of metals increases with atomic number because the ionization energy decreases.

In periods, reactivity of metals decreases when atomic number increases because the ionization energy increases.

Nonmetals reactivity trend

In groups, reactivity of non-metals decreases when atomic number increases because the electronegativity decreases

Relate to size- it increases.

In periods, reactivity of non-metals  increases with atomic number because the electronegativity increases.

Relate to size- radii decreases

Remember, the radii would have an effect on this

Density: in general

Density of solids is greatest Measured in g/cm3 Highest in center of table (d- block)

Density of gases Measured in g/L at STP (1atm , 0°C) Decreases as you go down a group Decreases as you go across the table

Density of liquids Measured in g/mL Density of Hg is greater than that of Br2

Density

Density v atomic number

To sum it up…

Summing it up (again)

Summary chart again