Periodic Table

1860 60/92 elements were known, but disagreements over average atomic masses.

1st Int’l Congress of Chemists (1860) decided actual #’s & some other properties.

But still no formal arrangement of elements

Dimitri Mendeleev (Russian) arranged elements in order of and similar properties.

Some of the other contenders…

And still some more…

Mendeleev found the properties of themselves periodically

1869 – 1st Periodic Table was published (p.162)Mendeleev made some exceptions – I(127) & Te(128).

He swapped them around to keep the similar properties in order.

He also had gaps for undiscovered elements, but he could predict their wt & properties, etc…

1911 – Henry Mosley (English) analyzed data and rearranged the elements according to their

therefore fixed I/Te problem & others.

Mosley’s table is the basis for thee Periodic Table.

The Periodic Table is an arrangement in order of Atomic # so that

The table contains rows called Periods. The columns are known as Groups or Families.

Since Mendeleev, some new groups/families were discovered & added to P.T

e.g. Noble Gases (group 18) unreactive gases.

Also Lanthanides: 14 elements Ce(58) – Lu(71)

And Actinides: 14 elements Th(90) – La(103)

The column number is it’s

Groups 1&2 and Groups 13-18 together are known as the Main Group.

Group 18 (Noble Gases) has a filled shell – stable octet. The valence shell determines the element’s chemical properties.

Let’s focus on the Main group only for now:As you go along:-

Period 1 E level 1(s) is fillingPeriod 2 2(s&p)Period 3 3(s&p)Period 4 4(s&p) etc…

Now focus on groups 3-12:Period 4 E level 3d is filling Period 5

Period 6

Period 7 adding 10 elements to each row.

Now focus on Periods 6&7 between Groups 3&4:

4f is filling adding 14 elements to row 6 &

5f row 7.

(see p.129 Figure 5-5)

Based upon which sublevel is filling up, the P.T. is divided into 4 blocks.

s-block

p-block

d-block

f-block (separated block)

s-block Elements

Li: [He] 2s1

Mg: [Ne] 3s2

s-block (Groups 1&2)- very reactive. Grp 1 > Grp 2Grp 1 (family name) (except H)- silvery & soft,- Not found pure in nature, reacts with H2O- Valence shell is ns1 (e.g.’s? Li, Na,K..)

Li in water Na in water K in water

Grp 2 metals- harder, denser, stronger than Grp 1- Less reactive, also not found pure in nature- Valence shell is ns2

- (e.g.’s? Be, Mg, Ca..)

p-block Elements B: [He] 2s22p1

C: [He] 2s22p2

N: [He] 2s22p3

O: [He] 2s22p4

F: [He] 2s22p5

Ne: [He] 2s22p6

p-block (Grps 13-18, except He)- p sublevel filling trying to achieve - i.e. trying to achieve ns2 np6

- # valence e-’s = Group # - 10- RHS contains all non-metals (except H&He)- LHS contains (semi-conductors)

- - have metal & non metal properties- - brittle solids e.g. Si, Ge

Contains p-block metals - harder & denser than s-block- only found as compounds in nature e.g. Sn, Pb

- Grp 18 known as (ns2np6)- Grp 17 known as (ns2np5)

- - most reactive non-metals- - reacts with most metals to form salts

Grp 16 known as family (ns2np4)

Grp 15 known as family (ns2np3)...

The “special” elements:

H is placed above Grp 1 1s1

He is placed above Grp 18 1s2

Ti: [Ar] 4s23d2

Fe: [Ar] 4s23d6

Zn: [Ar] 4s23d10

d-block Elements

f-block Elements

Ce: [Xe] 6s2 4f6

Th: [Rn] 7s2 5f2

d block: (Grps 3-12)- a.k.a. the - - good conductors, high lustre- - less reactive than Grps 1&2 can be

found in nature.

f-block: (Periods 6&7 between Grps 3&4)- Lanthanides (Per.6) shiny metals & react like

Grp 2 (note valence shell)- Actinides (Per.7) radioactive

Periodic Trends A trend is a generalization about how that

particular characteristic changes as you move around the table

First you need to understand

Then you can rationalize the trend (to avoid having to memorize!!)

Periodic TrendsAtomic Radii: How big is the atom in question…

need to know where the

The radius is determined by half the distance between atoms of the same element.

Across a Period: the # p+’s & e-s are increasing, so the difference in charge is increasing

greater force of (stronger pull on the e-s)

smaller radius.

Down a Group: e-s occupy E levels that are further from the nucleus

larger radius.

Periodic Trend

See p.141 Fig 5-13

Main Group, s & p blocks

`

Ion

Ion:

: atom that has a +ve charge (A+).

i.e. missing an e-

: atom that has a –ve charge (X-).

i.e. has an extra e-

Ionization EnergyIonization: process by which an +ve.

i.e. A + Energy A+ + e-

Ionization Energy: energy e- from an atom. (usually a metal).

The smaller the atom the the electrons are to remove… pulling something out of a tight grip vs lose grip

It becomes more difficult to remove each successive e- from the same atom.

Therefore, 2nd, 3rd,… Ionization Energy values are

Periodic Trends of Ionization Energy.

Discuss whyAcross: Force of attractionDown: Valence shell radius

Electron Affinity:- loosely defined as: how badly the atom wants

to an electron. More so as the atom nears a stable octet. Less so for metals.

- officially: the Energy released when a gaseous neutral atom gains an electron.

X + e- X- + Energy (kJ)(see CD 8:13 Cl animation of EA)

Periodic Trends:Across a Period: the becomes a larger

negative #. (it’s like a bank withdrawal, but in Energy terms)

Down a Group: it’s harder to e-’s because atoms would rather lose them. low EA #’s.

i.e not willing to “pay” muchPeriodic Trends Period 2&3 Main Group elements

Play “Electron Affinities” ani& “Period Trend: Electron Affinity” ani.

Ionic Radii:

Cation: ion – missing e-’s, tend to be metals. smaller radius (Eg)

Anion: ion – extra e-’s, tend to be non- metals. larger radius(Eg)

Periodic Trend:

ElectroNegativity (EN):Compound: where 2 or more elements are

together.

e.g. NaCl , CO2 , H2O , C6H12O6

Valence e-’s in a chemical compound are concentrated closer to one atom rather than the other.

A-----eee--X

(m) (nm)

valence e-’s of A & X

e.g Na----Cl

This uneven concentration of charge has an effect on the chemical properties of a compound.

: is a measure of the ability of an atom in a chemical compound to attract e-’s.

The most electronegative element is: (the most NON metallic)

and is given an arbitrary value of 4.0(why not 5,10)The least electronegative element is:

(the most metallic)And is given a value of 0.7 based on comparisons

with F.

Metals (LHS of PT) tend to have EN

Non Metals (RHS of PT) tend to have EN

As you go across a Period, EN value increases

As you go down a Group, EN value decreases

3-D version of EN diagram

increases

Discuss Electronegativity (EN) vs Electron Affinity (EA)Also do summary of all the trends.