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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.
Charactaristics of elements of group
Stability of a nucleus and its binding energy
conductometric titratins : weak base within a weak acid
(a) Co-ordination compound A co-ordination compound contains a central metal atom or cation which is surrounded by a suitable number of anions or neutral molecules and usually re
Classification of polymers - Thermoplastics These are the polymers that can be simply softened repeatedly while heated and hardened when cooled along with little change in the
merits
Q. What is the basic structure of Alkynes? Ans. Alcohols have the general chemical formula of ROH. The R stands for the rest of the molecule and is usually an alkyl group
NITROGEN Nitrogen is the great strength of the triple bond makes N2 thermodynamically and kinetically stable but moderately electronegative element. The atom can form three sing
In Bohr's model, atomic radius of the first orbit is γ the radius of the 3rd orbit, is: (1) γ/ 3 (2)γ (3) 3γ (4) 9γ Ans: 9γ
Limitations of second law of thermodynamics
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