Q1. Explain with examples:
i) Doberiener’s law of Triads
ii) Newland’s law of Octaves
Q2. Define
following:
Mendeleev’s Periodic law,
Periodicity, periodic trend,
modern, periodic law,
Lanthanides, Trans Uranium elements
Q3. State Moseley’s Periodic law. What is the
basis of periodic classification? Discuss in detail the long form of periodic table.
Q4. Compare the properties of Alkali metals
and halogens. Give names of their members.
Q5.Give salient
features of group VIIIA. Give their general electronic configuration.
Q6. Write down the names of member elements
of Alkaline Earth metals. Give their General characteristics.
Q7.What are
lanthanides and actinides? Are they d or f –block elements?
Q8. An element has the atomic number (3 to 20). Give its Electronic
configuration. Identify its period and group. Write down three characteristics of the belonging group.
Q9. If an element
contains two shells only and its outermost shell contains 5 electrons, then to
which group the element
belongs in the periodic table? Name the element. Predict its period.
OR
If an element contains two
shells only and its outermost shell contains 4 electrons, then to which group
the element belongs in the
periodic table? Name the element. Predict its period.
Q10. What are transition
elements? Give their types. Give their 4 general properties.
Q11. Identify that which halogens exist as gases,
liquid and solid?
Q12.Discuss that Mendeleev periodic law provide a
base for modern periodic table
Q13. Explain the similarity of chemical and physical properties of
elements in the same family
Q14. Distinguish between periods and groups. Explain briefly the
periods of modern periodic table.
Q15. Justify that
periodicity of properties dependent upon number of protons in an atom?
Q16. Identify the electronic configuration of the
following elements; Na, Ca, F, Si
Q17. Determine the demarcation of periodic table in to s, p, d and f
blocks.
Q18. Describe the trend of electronegativity within
group and period with the help of examples?
Q19. Why Alkaline earth metals shows irregular
melting and boiling point?
Q20.Why ionization energy, electron affinity and
electronegativity exhibit same trend in period and groups?
Q21. Determine the location of families on periodic
table.
Q22. Explain how shielding effect influence the periodic trends?
Q23.Define, give their units, their dependence and periodic variation of the following periodic properties of elements;
atomic radii, ionization energy, electron affinity, electronegativity.
Answer
Doberiener’s law of
Triads
“Central atom of each set of triad has an atomic mass average of
the atomic masses of the other two elements.”
For example,
calcium (40), strontium (88) and barium
(137) in which atomic mass of strontium is average of atomic masses of calcium
and barium.
Newland’s law of Octaves
In 1864, an
English industrial chemist John Newland proposed his Law of Octave accordingly:
“If the elements are arranged in the ascending order of their
atomic weights, the eighth (8th) element following any given element
in the series has nearly same properties as first one i.e. its properties are a kind of repetition of the first.”
For example,
Na is the 8th element from Li has similar properties, Mg is the 8th
element following Be and has same properties etc.
Answer
Mendeleev’s Periodic
law
“The properties of the elements are a
periodic function of their atomic weights.”
Periodicity
The
Periodicity means” Repetition of something after fixed interval”. The
Periodicity of properties means that elements are arranged in an Order where
properties of elements repeat after some period.
modern periodic law
The physical and chemical properties of
all elements are the periodic function of their atomic numbers.
periodic trend
The variation
in properties of elements along a period in the periodic table is called
periodic trend.
Lanthanides
The 14
elements series of f-block elements in 6th period in the periodic
table after 57La in which 4f orbital is filled is called lanthanides
series. It is from 58Ce to 71Lu.
Trans Uranium elements
The elements
following uranium in the periodic table are called trans uranium elements e.g.
Es
Answer
Atomic
number is a fundamental property of an atom because it increases regularly
element to element and is fixed for every elements. Atomic number also provides
the electronic configuration of elements of periodic table.
A British
physicist, Henry Moseley in 1914 showed that atomic number (number of protons)
of an atom is the fundamental and basic property. The modern periodic
table is the result of discovery of atomic number by Moseley in 1914. Based on
the concept of atomic number Bohr, Werner and Bury proposed the modern
periodic law which states that:
The physical and chemical properties of all elements are the
periodic function of their atomic numbers.
Basis of Classification
The periodic
classification of elements is based on periodicity, due to which the
elements having similar properties are repeated at regular intervals. As atomic
number is related to the number of protons in an atom, so the real basis of
periodicity of properties is due to recurrence of identical valence shell
electronic configuration of the next element in the same group.
The periodic
table is a tabular form of the known elements in which elements are placed in
the increasing order of their atomic number or electronic structure
(configuration) so that many chemical properties vary regularly across the
table.
The modern
periodic table based on Mosley’s Modern Periodic Law grounded on periodicity
adopted by IUPAC in 1984 is also known as Bohr’s Long Form of Periodic Table
(because it contains 16 groups or 18 vertical columns rather than 8 and 7
periods instead of 12).
Answer
Difference
between Alkali Metals and Halogens
Members of
group IA
This group
comprises of fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine
(At). Except astatine which is a metalloid and radioactive all others are
non-metals.
Members of
group VIIA
This group
includes lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs)
and francium (Fr). Francium is radioactive. Sodium and potassium are the 6th
and 7th most abundant elements in the earth crust with % abundance
of 2.6% and 2.4% respectively.
Answer
Group VIIIA or Zero Group (Inert or Noble Gases)
Members
This group includes helium (He), neon (Ne), argon (Ar), krypton (Kr),
xenon (Xe) & radon. Radon (radioactive)
General Characters
1. They are monoatomic,
diamagnetic and low boiling point colourless gases.
2. They
are have ns2 np6
valency shell configuration (where n = 1 – 6) i.e. they have 8 valence electrons (except helium
which has only two valence electrons i.e. 1s2).
3. They
have complete valence shell i.e. an octet or duplet (He) of electrons
in their valence shell. They are exceptionally stable due to completely
filled valence shell.
4. They
are chemically inert or non-reactive due to completely filled outer
shell
Answer
Members
This group
comprises of Beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr),
barium (Ba) and radium (Ra). Radium is radioactive.
General
Characters
1.They are less
reactive and less electropositive than alkali metals, a bit
harder having relatively high melting and boiling points than the
alkali metals.
2.They have ns2 valency shell electronic
configuration i.e. contain two valence electrons and are divalent.
3. They lose
their two valence electron on reaction to form divalent positive ion (M2+).
4. They are reducing agent due to the low I.P.
5. They form ionic bond except Be and Mg.
6. They
show irregular densities and melting and boiling points.
Answer
Lanthanides
The 14
elements series of f-block elements in 6th period in the periodic
table after 57La in which 4f orbital is filled is called lanthanides
series. It is from 58Ce to 71Lu.
Actinides
The 14
elements series of f-block elements in 7th period in the periodic
table after 89Ac in which 5f orbital is filled is called actinides
series. It is from 90Th to 103Lr.
Lanthanides
and actinides are f-block elements in which f-orbital is progressively filled.
Answer
Since element
contains only two shells, its period is 2.
Since element
has 5 valence electrons, its group is VA.
The element
present in 2nd period belonging to group VA is nitrogen with Z = 7.
OR
Since element contains
only two shells, its period is 2.
Since element
has 4 valence electrons, its group is IVA.
The element
present in 2nd period belonging to group IVA is carbon with Z = 6.
Answer
Definition of Transition Elements
The elements in which besides the valence shell, penultimate shell
is also incomplete i.e. in which electrons are in the process of occupying d or
f sub-shells (orbitals) are called transition elements.
Characteristics
of Transition Elements
1. They all are
metals.
2. They show variable valencies (forming more than one type of ions)
e.g. Cu1+, Cu2+,
Fe2+, Fe3+ etc.
3. Their
valence shells are incomplete.
4. They form coloured compounds
e.g. ferric salts are brown.
5. They all are paramagnetic
except Zn, Cd, Hg.
Classification of Transition Elements
They consist
of following types:
1. Outer Transition Elements
The elements
of sub-group B from IB, IIB, IIIB to VIIIB are called Outer Transition Elements
which are characterized by filling of penultimate d-sub-shell with outer
s-sub-shell. They have partially filled d-sub-shell. That is why they
are called d-block elements. They consist of four series of 10
elements each.
2. Inner Transition Elements
The elements which are characterized by filling of penultimate f sub-shell with outer s-sub-shell having partially filled f sub-shell are called Inner Transition Elements or f-block elements. They are placed at the bottom of the periodic table. They consist of two series of 14 elements each
Answer
In 1869 Mendeleev proposed a periodic
law on the basis of physical and chemical properties empirically. which states
that
“The properties of the
elements are a periodic function of their atomic weights.”
Features of Mendeleev’s Table
The Mendeleev’s periodic table consisted
of 8 vertical columns called groups (i.e. group I to VIII) containing similar
elements and 12 horizontal rows called Series or Periods having dissimilar
elements. The group number indicates the highest valency of the element of that
group. In certain cases Mendeleev left gaps, which modified by Moseley.
Atomic
number is a fundamental property of an atom because it increases regularly
element to element and is fixed for every elements. Atomic number also provides
the electronic configuration of elements of periodic table. It was noticed in
arrangement of elements that atomic number increases from left to right in a
horizontal row and properties of elements were found repeating after regular
intervals. Due to this reason elements of same properties and same electronic
configuration are placed in same group.
Answer
Elements in
the same group have same valence shell electronic configuration. Since chemical
properties of elements depend on number of valence electrons or valence shell
electronic configuration, hence elements in the same group have same chemical
properties. For example all elements of group IA have same ns1 configuration so
they have same chemical properties i.e. they all are metals, showing fixed
valency of 1, forming ionic bond etc.
First period (shortest
period)
1. This period
contains only two elements Hydrogen (H) and Helium (He).
2. This period
corresponds to filling up of K-shell.
Second and Third Period (Short Period; Period 2 and 3 are Short Periods as each contains 8 elements.
1. Each periods
contain eight elements (3Li to 10Ne and 11Na
to 18Ar respectively)
2. In these
Periods L and M shells are being filled by electrons respectively.
3. Second period
contains Li, Be, B, C, N, O,F and Ne.
4. Third period
contains Na, Mg, Al, Si, P,S, Cl, and Ar.
Fourth and Fifth Period (Long Period; Period 4 and 5 are Long Periods as each contains 18 elements.
1. Each period
contain 18 elements (19K to 36Kr and 37Rb to 54Xe
respectively).
2. In these
periods N and O shells are being filled by electrons.
3. Fourth period
starts from Potassium (K) and ends on Krypton (Kr).
4. Fifth period
starts from Rubidium (Rb) and ends on Xenon (Xe).
Sixth Period (Longest Period)
1. This period
contains 32 elements.
2. This periods
starts from Cesium (Cs) and ends with Radon (Rn) (i.e. 55Cs to 86Rn).
3. This period
contains a group of 14 elements at the bottom called as Lanthanides.
Seventh Period (Incomplete Period)
1. This period is
considered as incomplete (as to date about 112 elements have been discovered)
2. This period
starts from Francium (Fr)
3. This period
contains a group of 14 elements at the bottom known as Actinides.
Answer
The Periodicity means” Repetition of
something after fixed interval”. The Periodicity of properties means that
elements are arranged in an Order where properties of elements repeat after
some period.
The periodic
classification of elements is based on periodicity, due to which the
elements having similar properties are repeated at regular intervals. As atomic
number is related to the number of protons in an atom, so the real basis of
periodicity of properties is due to recurrence of identical valence shell
electronic configuration of the next element in the same group.
According to Modern Periodic Law, the properties of elements are periodic function of their atomic number which in turn is related to electronic configuration. The electronic configuration gives relationship between valency, I.P, E.A, Atomic Volume, E.N., Density, Metallic Character, M.P and B.P etc.
Answer
The periodic
table has been divided into following 4 blocks on the basis of electronic
configuration:
1. Representative
Elements (s-block and
p-block elements)
2.Noble Gases
3. Outer transition elements (d-block
Elements)
4. Inner transition elements (f-block
Elements)
1. Representative Elements
Definition
The elements of sub-group A are called Main group or
Normal or Major or Representative Elements
as the properties of these elements are represented by valence electrons.
s-block and p-block elements except inert gases are known as representative
elements. They form group IA to VIIA and are present at left and right side of the
periodic table. Their general valence
shell electronic configuration of ns1, ns2 to ns2
np5 (ns1-2 to ns2 np1-5).
Characters
1.They consist of some
metals (IA and IIA Groups, some elements of IIIA group, Pb, Bi etc.), all non-metals and metalloids(B, Si, Ge, As, Sb, Se, Te).
2. Some elements are diamagnetic and
some are paramagnetic.
(a) s-block Elements
The elements
in which outer electrons enter into s-orbital having ns1-2
(i.e. ns1 to ns2) valence shell configuration are called s-block elements. They form group IA and IIA
of periodic table found at its far left side.
(b) p-block Elements
The elements
in which outer electron enters into p-orbitals having ns2 np1-6
valence shell configuration are called p-block elements. They from Group IIIA to Group VIIIA of the periodic
table and are located at the extreme right of the periodic table. There are
total 30 elements in six sub-groups of p-block including noble gases
except helium.
2. Nobel gases
1.They are colourless,
unreactive and diamagnetic gases.
2. They are place in
zero or VIIIA group
3.Their valence
shell configuration ns2 np6
4. They are
exceptionally stable.
3. d-Block Elements/Outer Transition Elements
Definition
The elements of sub-group B in which
last electron enters into (n–1)d-orbitals( in their atomic state or ionized
state or in their common oxidation states) are called d-block elements. Their
valence shell electronic configuration (n–1)d1-10, ns2
Characters
They all are metals characterized by their variable
valencies, forming coloured compounds and their ability to form
complex ions. they show
common oxidation state.
Sub-division
The outer
transition (d-block) elements consist of following 4 series of 10
elements each:
4.InnerTransition Elements
The elements in which last electron enters into inner
(n–2)f-orbitals i(n their atomic state or ionized state or in their common
oxidation states) are called f-block elements. Their valence shell electronic
configuration (n–2)f1-14, (n–1)d1, ns2
Sub-division
f-block
consists of two series of 14 elements each namely Lanthanide Series and
Actinide Series.
(a) Lanthanides (4f)
series in 6th period ; following 57La and it is from58Ce to 71Lu
(b) Actinides (5f)
series in 7th
period ; following 89Ac and
it is from 90Th to 103Lr
No comments:
Post a Comment