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ORIGIN AND ABUNDANCE OF THE ELEMENTS
The synthesis of elements needs nuclear reactions, of which the most important type is the fusion of two light nuclei to prepare one of higher mass and charge. The attractive strong interaction, which holds neutrons and protons together, operates only over very short distances (around 10-15 m) and is opposed at longer size by the electrostatic repulsion between positively charged protons. To get two nuclei close enough together for fusion needs enormously high energies, which are usually found only at high temperatures (above 107 K) in the interior of stars. Under such conditions the chemical properties of components are irrelevant, as no compounds may exist, atoms being in highly ionized states stripped of their electrons.
Gases thrown out by a supernova cool, and can subsequently be incorporated into new stars. The formation of planetary systems can be common in the Universe. Studies suggest that other planets and the Earth formed about the same time as the Sun. While the Sun formed at the center, chemical reactions in the cooler outer parts of the gas concentration produced solid particles, which collected under gravitational forces, first into small bodies known as planetesimals, and subsequently into the planets. In the outer parts of the Solar System temperatures were low enough to form 'ices' of water, carbon dioxide, solid methane and ammonia, which are constituents of the giant planets Saturn and Jupiter.
(a) Explain in terms of ionic equilibria why the aqueous solution of a salt derived from a weak acid and a strong base (e.g. sodium phenolate) has a pH greater than 7. (b) B
Difference between thermoplastic and thermosetting polymers Thermoplastic polymers Thermosetting polymers (1) Thermoplastic polymers
Which of the following metal ions will have maximum number of unpaired electrons: (1) Fe +2 (2) Co +2 (3) Ni +2
Raising heavy weights by water pressure Get a rubber hot-water bottle. Put a one- hole stopper carrying a short glass tube tightly in the neck. Punch a hole in the bottom of a
K3[Al(C2O4)3]
Why there are tie lines for 3 phase equilibrium however not for 2-phase equilibrium in a two-component system? Lever rule derived from mass balance gives the relative amounts o
i need complete assignment on it
when 100ml of M/10 H2S04 is mixed with 500ml of M/10 NaOH then nature of resulting solution and normality of excess of reactant left isum 100 words accepted#
Which electronic configuration is not observing the ( n+ 1) rule: (1) 1s 2 , 2s 2 , 2p 6 , 3s 2 , 3p 6 , 3d 1 , 4s 2 (2) 1s 2, sp 2 , sp 6 , 3s 2 , 3p 6 , 3
properties of oxidation
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