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Assumes that electron pairs are arranged around the central element of a molecule or polyatomic ion so that there is maximum separation (and minimum repulsion) among regions of high electron density.

 

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Helium

Discovered : by Sir William Ramsay in London, and independently by P.T. Cleve and N.A. Langlet in Uppsala, Sweden in 1895.
Origin : The name is derived from the Greek ‘helios’,sun.
Description :A colourless, odourless gas that is totally unreactive. It is extracted from natural gas wells, some of which contain gas that is 7% helium. It is used in deep sea diving for balloons and, as liquid helium, for low temperature research. The Earth’s atmosphere contains 5 parts per million by volume, totalling 400 million tons, but it is not worth extracting it from this source at present.
Atomic No:2 MAss No:4

Alpha (a) Particle

Helium ion with 2+ charge, an assembly of two protons and two neutrons.

Electrode Potentials

Potentials, E, of half-reactions as reductions versus the standard hydrogen electrode.

Radiation

High energy particles or rays emitted during the nuclear decay processes.

Capillary Action

The drawing of a liquid up the inside of a small-bore tube when adhesive forces exceed cohesive forces, or the depression of the surface of the liquid when cohesive forces exceed the adhesive forces.

Binary Acid

A binary compound in which H is bonded to one or more of the more electronegative nonmetals.

Nernst Equation

Corrects standard electrode potentials for nonstandard conditions.

Cohesive Forces

All the forces of attraction among particles of a liquid.

Three ways to make patina at home

The first way is ammonia patination. To do this, take a plastic container. Put a couple of paper or ordinary towels at the bottom. Moisten them with ammonia. Then sprinkle with large table salt.

Supercritical Fluid

A substance at temperature above its critical temperature.