8.
State and explain Heisenberg's uncortainity principle?
9.
State and explain De-broglie's wave theory?
III. Answer the Following Questions
10. What are postulates of Bohr's theory? Explain H-spectrum with limitations
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Write an essay on sp,d and f block elements?
Answers
Answer:
8) Heisenberg’s uncertainty principle states that it is impossible to measure or calculate exactly, both the position and the momentum of an object. This principle is based on the wave-particle duality of matter.
9)De Broglie's hypothesis of matter waves postulates that any particle of matter that has linear momentum is also a wave. The wavelength of a matter wave associated with a particle is inversely proportional to the magnitude of the particle's linear momentum.
10)THE MAIN POSTULATES OF BOHR'S ATOMIC THEORY ARE:
.The electrons revolving around the nucleus are confined to certain fixed orbits called shells or energy levels ,each of which is associated with a fixed amount of energy.
. While it is revolving around the nucleus in an orbit, an electron neither loses not gains energy.
11)The s-block is one of four blocks of elements in the periodic table. The element of s- group have a common property. The electron in their most outward electron shell are in the s-orbital. Elements in the s- are in the first two periodic table groups. The elements in group one are called the alkali metals.
The p-block is on the right side of the periodic table and includes elements from the six columns beginning with column 13 and ending with column 18. Helium, though being in the top of group 18, is not included in the p-block. This contains variety of elements and is the only block that contains all three types of elements: metals, nonmetals, and metalloids. Generally, the p-block elements are best described in terms of element type or group.
The d-block is on the middle of the periodic table and includes elements from columns 3 through 12. These elements are also known as the transition metals because they show a transitivity in their properties i.e. they show a trend in their properties in simple incomplete d orbitals. Transition basically means d orbital lies between s and p orbitals and shows a transition from properties of s to p. The d-block elements are all metals which exhibit two or more ways of forming chemical bonds. Because there is a relatively small difference in the energy of the different d-orbital electrons, the number of electrons participating in chemical bonding can vary. This results in the same element exhibiting two or more oxidation states, which determines the type and number of its nearest neighbors in chemical compounds.
The f-block is in the center-left of a 32-column periodic table but in the footnoted appendage of 18-column tables. These elements are not generally considered as part of any group. They are often called inner transition metals because they provide a transition between the s-block and d-block in the 6th and 7th row (period), in the same way that the d-block transition metals provide a transitional bridge between the s-block and p-block in the 4th and 5th rows. The known f-block elements come in two series, the lanthanides of period 6 and the radioactive actinides of period 7. All are metals. Because the f-orbital electrons are less active in determining the chemistry of these elements, their chemical properties are mostly determined by outer s-orbital electrons. Consequently, there is much less chemical variability within the f-block than within the s-, p-, or d-blocks.
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