Physical science Important Questions
A. The physical and chemical properties of elements are a periodic function of their atomic weights
2. What is valency?
A. Valency of an element was defined a the combing power of an element with respect to hydrogen.
3. Write the units of ionization Energy.
A. eV (or) Kcal/mole (or) KJ/mole
4. Give any two examples of Dobereiner's traid.
A. i) Li , Na , K ii) S ,Se,Te
5. Write the electronic configuration of Transition elements.
A. Ns²np⁶ (n-1) d¹–¹⁰
6. Write the Nobel gas elements.
A. He,Ne,Ar,Kr,Xe,Rn
7. Who is the father of periodic table
A. Mendeleev
8. What are Lanthanides ?
A. Elements acquiring same properties are called Lanthanides i.e 4f elements. They are from 58ce (cerium) to 71Lu (Lutetium)
9. Explain how the elements are classified into s,p,d and f-blocks elements in the periodic table and give the advantage of this kind of classification
A. 1) Depending upon to which sub-shell the differentiating electron enters the elements that are classified into s,p,d and f-blocks elements.They are:
i) s-block elements
ii) p-block elements
iii) d-block elements
iv) f-block elements
2) If the differentiating electron enters in s-sub shell then the elements are called s-block elements. IA(1), IIA(2) group elements belong to this block.
3) If the differentiating electron enters in p-sub shell then the elements are called p-block elements. IIIA(13), IV A (14), VA (15), VI A (16), VII A (17) belongs to p-block.
4) If the differentiating electron enters in d-sub shell then the elements are called d-block elements. IB, II B, III B, IV B, V B, VI B, VII B, VIII B belongs to d-block elements. They are also called as 'transition elements'.
5) If the differentiating electrons enter in f- sub shell then the elements are called f- block elements. These are divided into two types:
i) Lanthanides (4f elements).
ii) Actinides (5f elements).
These also called as 'inner transition elements'.
Advantage of this classification:
1) The systematic grouping of elements into groups made the study simple.
2) Each period begins with the electron entering a new shell and ends with the complete filling of s and p-sub shells of
that shell.
10. What is a periodic property? How do the following properties change in a group and period? Explain.
I. a) Atomic radius
b) Ionization energy
c) Electron affinity
d) Electronegativity
II. Explain the ionization energy order In
the following sets of elements:
a) Na, Al, Cl b) Li, Be, B
c) C, N, O. d) F, Ne, Na
e) Be, Mg, Ca
A. Periodic property: The property in which there shall be a regular gradation is called 'periodic property'.
I. a) Atomic radius
Period: Atomic radius of elements
decrease across a period from left to
right because the nuclear charge
increases due to increase in atomic number.
Group: Atomic radius increases from
top to bottom in a group due to addition
of new shell.
b) Ionization energy:
Period: When we move from left to
right it does not follow a regular trend
but generally increases due to increase
in atomic number.
Group: In a group from top to bottom,
the ionization energy decreases due to
increase in atomic size.
c) Electron affinity:
Period: Electron affinity values increases from left to right in a period.
Group: Electron affinity decreases from top to bottom in a group.
d) Electronegativity:
Period: Electronegativity increases from left to right in a period.
Group: Electronegativity values decreases from top to bottom in a group.
II. Ionization energy order:
a) Na<Al<CI b) Li<B<Be
c) C<O<N. d) Na<F<Ne
e) Ca<Mg<Be