A metal in the first column of the periodic table (i.e., lithium, sodium,
potassium, rubidium, caesium and francium). With the exception of francium,
these metals are all soft and silvery.
They may be readily fused and volatilized with their melting and boiling
points becoming lower with increasing atomic mass. They are the strongest
electropositive metals. These elements react vigorously, even violently with
water.
The alkali metals are silver-colored (caesium has a golden tinge), soft,
low-density metals, which react readily with halogens to form ionic salts,
and with water to form strongly alkaline (basic) hydroxides. These elements
all have one electron in their outermost shell, so the energetically
preferred state of achieving a filled electron shell is to lose one electron
to form a singly charged positive ion, or cation.
Hydrogen, with a solitary electron, is usually placed at the top of Group 1
of the periodic table, but it is not considered an alkali metal; rather it
exists naturally as a diatomic gas.
Removal of its single electron requires considerably more energy than
removal of the outer electron for the alkali metals. As in the halogens,
only one additional electron is required to fill in the outermost shell of
the hydrogen atom, so hydrogen can in some circumstances behave like a
halogen, forming the negative hydride ion.
Binary compounds of hydride with the alkali metals and some transition
metals have been prepared. Under extremely high pressure, such as is found
at the core of Jupiter, hydrogen does become metallic and behaves like an
alkali metal
Thanks,
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-----Original Message-----
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of Sundaram Sundaram
Sent: Saturday, December 18, 2010 2:40 PM
To: Materials & Welding
Subject: [MW:8786] Painting System
Hi Friend,
1) In my project i have seen the midcoat painting
system description as a high solid,high build,polyamide cured two-
coponent epoxy coating.In this which is the solvent.Can anyone help to
find it.
2) what is the difference between the painting and
coating inspector?
3) what is the difference between the alkyl and
alkyd
Please clarify these things.
with thanks & regards,
sundaram
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