Trends of the periodic table

Trends of the periodic table

11/3/2009Mr.Johnson Chemistry 4J1

Group II Group VII Period III


CXC Objectives for Trends of the Periodic Table:


1. Explain the basis of the arrangement of elements in the periodic table. A2.7

2. Explain the connection between atomic structure, oxidation state and the position of the periodic table. A2.8

3. Anticipate properties of unknown elements based on group trends. A2.9

4. Identify trends in group II. A6.15. Identify trends in group VII A6.26. Identify trends of period 3 using gradation from

metallic to non-metallic properties. A6.3

Elements are arranged by increasing numbers of protons(atomic number):


Dmitri Mendeleev was the first to propose arranging elements in order of their increasing atomic number or numbers of Protons, grouping elements with similar behaviuor into similiar areas of the periodic table. It works something like this:

And so on...

Elements of the same period have increasing numbers of electrons in their outer shells:


Elements of the same period have increasing numbers of electrons in their outer shells:


11/3/2009Mr.Johnson Chemistry 4J7 Elements of group 1 have only 1 electron in their outer shell.

Elements of group 2 have only 2 electrons in their outer shell.

Elements of group 6 have 6 electrons in

their outer shell.

And so on...

Atomic Radius:

11/3/20098

As the numbers of protons of each atom increases the numbers of electrons it has also increases. These electrons go into more and more shells increasing the overall size or atomic radius of the atom.

Atoms with 1 or 2 electrons in their outer shell Form bonds by losing electrons producingpositively charged ions, E.g Na+ , K+ and Mg2+

Which groups of the periodic table have 1 or 2 electrons in their outer shell?

Atomic radius Cont’d:


Trends of Group II, Group IIV and Period 3


Atomic Radii: The distance accross from one side of an atom

to the other.

Ionization energy: Amount of energy it takes to liberate the electrons from the outer shell of the atom.

Reactivity: The tendency of an element to partake in chemical reactions.

Metallic characteristics: The tendency of an element to form stable ions by losing electrons rather than gaining them.

Melting point & boiling points

Ionization energy:


The electrons of the outer shell are under the influence of the pull of protons in the nucleus. The amount of energy it takes to overcome the pull of the nucleus and remove the electron from it’s orbit around the atom is called the ionization energy.

The more shells an atom has the more inner shell electrons there are to interfere with the pull between the outer shell electrons and the nucleus, hence the outer shell electrons are more loosely held by larger atoms than smaller ones.

Ionization Energy of some elements:

11/3/200912

Element First Second

Third Fourth Fifth Sixth Sevent

h Na 496 4,560Mg 738 1,450 7,730Al 577 1,816 2,881 11,600Si 786 1,577 3,228 4,354 16,100P 1,060 1,890 2,905 4,950 6,270 21,200S 999.6 2,260 3,375 4,565 6,950 8,490 27,107Cl 1,256 2,295 3,850 5,160 6,560 9,360 11,000Ar 1,520 2,665 3,945 5,770 7,230 8,780 12,000

Values given in Kj/molMetals, become stable by losing electrons so the energy

it takes to remove an electron and increase the stability of a metal is very low, as they in actual fact want to lose an electron anyway.

While non-metals which become stable by gaining electrons, very reluctantly give up their electrons, for them, losing an electron means moving further away from stability , therefore it takes alot more energy to remove an electron from a non-metal ,resulting in non-metals having typicaly the highest ionization energies.

http://en.wikipedia.org/wiki/Sodium

http://en.wikipedia.org/wiki/Magnesium

http://en.wikipedia.org/wiki/Aluminium

http://en.wikipedia.org/wiki/Silicon

http://en.wikipedia.org/wiki/Phosphorus

http://en.wikipedia.org/wiki/Sulfur

http://en.wikipedia.org/wiki/Chlorine

http://en.wikipedia.org/wiki/Argon

Trends of Ionization energy:


IONIZATION ENERGY INCREASES UP THE GROUP AND LEFT TO RIGHT ACCROSS THE PERIOD.

Question:


Which element has the least ionization energy and which the most?

Which of these elements is most likely to be a metal, non-metal or a stable noble gas?

Element X: ionization energy 1,255 Kj/molElement Y: ionization energy 432 kj/molElement Z: ionization energy 10,000 Kj/mol

WARNING :DO NOT ADVANCE TO THE NEXT SLIDE UNTIL YOU’VE

TAKEN A MINUTE TO THINK ABOUT THE QUESTION.

Answer:


Element X: ionization energy 1,255 Kj/mol = Non-Metal

Element Y: ionization energy 432 kj/mol = Metal

Element Z: ionization energy 10,000 Kj/mol = Noble gas

Reactivity Of metals:


The reactivity of metals is directly related to how loosely or tightly their nucleus holds the outer shell electrons.

Metals with smaller atoms such as Na and Be hold their electrons more tightly than Metals with larger atoms, as they have fewer inner shell electrons to interfere with the pull of the nucleus on the electrons in the outer shell. Such metals give up their electrons in chemical reactions relatively reluctantly.

Metals with smaller atoms more readily lose their outer shell electrons in chemical reactions, as their many layers of electrons between the nucleus and outer shells results in a weak “hold” on these electrons.

Hence as the atomic radius of Metals increases the reactivity or tendency of the metal to partake in chemical reactions also increases.

REACTIVITY OF METALS INCREASES DOWN THE GROUP. FRANCIUM IS THE MOST REACTIVE METAL

Reactivity of metals:


MOST REACTIVE

LEAST REACTIVE

Reactivity of Non-Metals


Elements on the right hand side of the table such as those in group 7 with 7 outer electrons are looking to gain 1 electron to become stable. They partake in chemical reactions where they can “snatch” an electron.

The amount of force their positively charged nucleus can exert on the electrons of other elements therefore will mean whether or not they will successfully grab an electron and a chemical reaction will take place.

The atoms of larger non metals have larger amounts of inner shell electron blocking the pull of their nucleus on electrons outside their atoms. Hence they will not be able to pull electrons to themselves as readily as the atoms of smaller non-metals.

The atoms of smaller non-metals have very few inner shells of electrons, the pull of their nucleus is very un-inhibited and they can very readily strip an electron off the atoms of other elements.

REACTIVITY OF NON-METALS INCREASES UP THE GROUP. FLOURINE IS THE MOST REACTIVE NON-METAL

Reactivity of Non-Metals:


MOST REACTIVE

LEAST REACTIVE

Further Resources:


Chemistry for CSEC, Heinemann, Revised edition: Pg .83

Chemistry for CXC by Norman Lambert and Marine Mohammed, Heinemann, Pg.66 Group II, Pg.85 Group VII and Pg.74 Period III

Periodic table(user friendly, One-click breakdown for each element) www.ptable.com

I WOULD ENCOURAGE YOU TO USE THESE RESOURCES AS MUCH AS POSSIBLE

http://www.ptable.com/

Documents

Trends of the periodic table