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Mendeleev's periodic law
Mendeleev stated that the periodic properties of elements are the periodic function of atomic mass.
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Achievements of Mendeleev's Periodic Table
1. It was grouping of elements according to the chemical properties.
2. The periodic table had gaps for the undiscovered elements.
3. The prediction of properties of undiscovered elements were correct.
4. It helped in systematic study of elements
2. The periodic table had gaps for the undiscovered elements.
3. The prediction of properties of undiscovered elements were correct.
4. It helped in systematic study of elements
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Define Representative Elements
The Groups of periodic table can divided into the two categories.
- Representative Elements
- Transition Metals.
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Types of Elements - s, p ,d and f Blocks
Elements in the group exhibit similar chemical behavior. The similarity is because of two factors:
- The same number of electrons in the outermost orbital.
- The same distribution of electrons in their outermost orbitals.
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Atomic Size Trend Down the Group
The number of energy levels increases moving down a group as the number of electrons increases. As a result, the distance between the nucleus and the outermost orbital increases and so the atomic radius increases.
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Trend in ionization energy down the group
Ionization energy decreases down the group due increase in the atomic size (addition of new shell).
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Electrongain enthalpy and electronegativity
Electronegativity of an element may be defined as the tendency of its atom to attract the shared pair of electrons towards itself in a covalent bond whereas electron gain enthalpy is the energy released when electrons are added to a neutral gaseous atom to form a gaseous anion.
