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Group II

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JustSHAYani JustSHAYani

on 9 February 2012

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Transcript of Group II

Group II Atomic Radius & Ionic Radius Ionisation Energy Decreases down the group
Down the group
Number of electron shells increase- Sheilding effect increases
NUmber of protons increase- Nuclear Charge increases
Increase in shielding more than outweighs the increase in nuclear charge
Effective nuclear charge decreases
Attraction of nucleus for valence electron decreases
Less energy required to remove outermost valence electron - Ionisation energy decreases Electronegativity Electronegativity is the relative ability of an atom to attract the bonding electron pair in a covalent bond.
Down the group
Atomic radius increases- therefore the outer electrons are more shielded from the attraction of the nucleus
Hence the bonding electrons are less strongly attracted to the nucleus.
Electronegativity decreases down the group

Melting point & Boiling point Reaction of Group II Elements
with Water & Oxygen The reaction of group II elements increases down the group to produce metal hydroxides and hydrogen gas Increases down the group
Down the group
Number of electron shells increase- Shielding effect increases
Number of protons increas- Nuclear Charge increases
Increase in shielding more than outweighs the increase in nuclear charge
Effective nuclear charge decreases
Attraction of nucleus for valence electron decreases
Atomic / Ionic radius increases Generally decreases down the group
Down the group
Distance of outer electrons from nucleus increases due to increase in number of electron shells
However, number of delocalised electrons and charge of the cation remains the same
Weaker attraction between metal cation and the electrons
Strength of metallic bond decreases
Less energy required to break metallic bond during a change in state
Melthing/ boiling point decreases Reaction of Group II with Oxygen The reaction of group II elements increases down the group. It burns in oxygen with a bright flame to form mono-oxides Physical Properties of
Group II elements Chemical Properties of
Group II elements Group II Compounds
and their Reactivty Thermal Stability of Group II Carbonates and Nitrates As we go down the group
Size of Group II cation increases in size
Charge density of cation decreases
Polarising power of cation decreases
Electron cloud of anion is less distorted
Thermal stability of Group II carbonates and nitrates increases Why does thermal decomposition occur?
Cation have high charge density
Large anions
Cations can distort the large electron clouud of the anion, weakening the C-O bond or N-O bond , leading to the decomposition General Characteristics of Group II elements Beryllium Many beryllium compounds are covalent instead of ionic due to the difficulty to form metal cation since it have a higher 1st and 2nd Ionisation Energy
Beryllium forms an amphoteric oxide and hydroxide
It is less reactive due to a layer of protective oxide on the surface
Beryllium salts are more thermally unstable compared to the salts of the other group II elements Reducing Power Since reducing agents are oxidised (i.e. lose eletrons), substances are better reducing agents if they lose electrons more easily. Hence the reducing power of Group II elements increases down the group. This is reflected by the more negative standard electrode potential values down the group. Why they are called S-block elements? The s-block elements refer to the elements in group I (alkali metals) and II (alkaline earth metals).

The meaning of s-block is that their outermost shell electrons are in s-orbitals. Similar electronic configuration In each group, elements have the same number of outermost (valence) electrons hence they have the same outer electronic configuration.

The number of valence electrons is the same as its group member. Done by

Justina
Dakshayani
Shabana
11S4 Bibliography http://www.chemguide.co.uk/inorganic/group2/properties.htmlhttp:

http://www.chemguide.co.uk/inorganic/group2/thermstab.html

http://chemistry.about.com/library/blperiodictable.htm

http://www.webelements.com/magnesium/

http://www.creative-chemistry.org.uk/alevel/module1/trends3.htm#table

http://www.adichemistry.com/engine.html#inorganic/p-block/group-14/carbonates/carbonates-bicarbonates-1.html

http://www.youtube.com/watch?v=B2ZPrg9IVEo

A level chemistry guide by CS Toh

Chemistry A-level Textbook fourth edition by E.N Ramsden Fixed Oxidation States In all their compounds these metals have an oxidation number of +2 and, with few exceptions, their compounds are ionic.
The reason for this can be seen by examination of the electron configuration, which always has two electrons in an outer quantum level.
These electrons are relatively easy to remove, but removing the third electron is much more difficult, as it is close to the nucleus and in a filled quantum shell.
This results in the formation of M2+. The ionisation energies reflect this electron arrangement. The first two ionisation energies are relatively low, and the third very much higher.
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