Section - A
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1. Define Modern Periodic law.
2 Noble gases have zero electron gain enthalpy. Why?
Which is large in size, Na* or kt. Why?-
What is screening effect ?
Write IUPAC name of compound with atomic number = 108.
5x3=15
Section-B . Perout
6. (a) Atomic radius of cation is smaller than present atom. Why?
(b) Write General Electronic configuration of d-block elements.
7. (a) What is ionisation enthaipy ? Ionisation enthalpy of N is more than that of O. Why?
b) What are isoelectronic species ? Whiclof the following are iscelectronic Nat, 0,CH, Nº,
Cat2, Mg+2, F
8. (a) What are important contribution of Mendeleeve's periodic table ?
b Halogens have highest electron gain enthalpy. Why?
a) What is electronegativity? What is the difference between electronegativity and electron
gain enthalpy?
(b) Predict period, block, group of the following elements : N, Mg
10. (a) Why f-block elements are placed at the bottom of the periodic table ?
(b) Mg+2is smaller than 02, although both have similar electronic structure.
Answers
ANSWER
1.the law that the properties of the elements are periodic functions of their atomic numbers. Also called Mendeleev's law. (originally) the statement that the chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights.
2.So, they can't accept an electron and so the enthalpy is zero. Electron gain enthalpy or electron affinity is the amount of energy released when an electron is added to the valence shell of neutral gaseous atom. NOBLE OR INERT gases are the elements in which outermost s, p subshells are completely filled.
section- B
6.aCations are always smaller than their parent atoms this is because they have lesser electrons, while their nuclear charge remains the same. The remaining electrons are, therefore held more tightly by the protons in the nucleus and thus their radii.are smaller than the parent atoms.
6.b d–block(transition elements) -(n–1) d1–10 ns0–2, where n = 4 – 7
7.a.But in case of Oxygen the configuration is one more than half filled configuration. So oxygen would readily loose an electron to attain a stable configuration that is half filled configuration. So first Ionization energy of nitrogen is more than first ionization energy of Oxygen.
7.bIsoelectronic Definition.Isoelectronic refers to two atoms,ions or molecules that have the same electronic structure and same number of valence electrons. The term means "equal electric" or "equal charge". Isoelectronicchemical species typically display similar chemical properties. ... For example: Isoelectronic ions.
8.bThe electron gain enthalpy for halogens is highly negative because they can acquire the nearest stable noble gas configuration by accepting an extra electron. Noble gases have large positive electron gain enthalpy. This is because the extra electron is placed in the next higher principal quantum energy levels.
8.aDmitri Mendeleev was a Russian chemist who lived from 1834 to 1907. He is considered to be the most important contributor to the development of the periodic table. His version of the periodic table organized elements into rows according to their atomic mass and into columns based on chemical and physical properties.
9.a.While electronegativity is the tendency of the atom to attract electron. The ability of an atom in a covalently bonded molecule to attract shared pair of electrons towards itself is known as electronegativity. Energy released when isolated gaseous atom accepts an electron is known as electron gain enthalpy.
10.aThe reason why Lanthanides and Actinides are located at the bottom of the periodical table is because of their properties and in the block in which electrons fill up. ... The reason why inner-transition metals are located at the bottom of the periodic table, separated from the rest is because they all fill the f-block.
10.bAnswer:
Oxygen and magnesium are isoelectronic species i.e. they have same number of electrons but differ in the magnitude of their nuclear charge.
Mg+2 ion has 12 protons in its nucleus and therefore exert higher effective nuclear charge compared to O2- which has 8 protons.
As a result, the inner shells and the valence shell electrons are more strongly attracted by the nucleus in Mg+2.
Therefore Mg+2 ion is smaller in size than O2- ion although both have same electronic structure.
9.b In attachment......
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