Question 1:
Which of
the following statements is not a correct statement about the trends
when going from left to right across the periods of periodic Table.
(a) The
elements become less metallic in nature.
(b) The
number of valence electrons increases.
(c) The
atoms lose their electrons more easily.
(d) The
oxides become more acidic.
(c) The atoms lose their electrons more easily.
(On moving from left to right across the periods of the periodic table, the non-metallic character increases. Hence, the tendency to lose electrons decreases.)
Question 2:
Element
X forms a chloride with the formula XCl2,
which is a solid with a high melting point. X would most likely be in
the same group of the Periodic Table as
(a) Na (b) Mg (c) Al (d) Si
Question 3:
Which element has
(a) two
shells, both of which are completely filled with electrons?
(b) the
electronic configuration 2, 8, 2?
(c) a
total of three shells, with four electrons in its valence shell?
(d) a
total of two shells, with three electrons in its valence shell?
(e) twice
as many electrons in its second shell as in its first shell?
(a) Neon has two shells, both of which are completely filled with electrons (2 electrons in K shell and 8 electrons in L shell).
(b) Magnesium has the electronic configuration 2, 8, 2.
(c) Silicon has a total of three shells, with four electrons in its valence shell (2 electrons in K shell, 8 electrons in L shell and 4 electrons in M shell).
(d) Boron has a total of two shells, with three electrons in its valence shell (2 electrons in K shell and 3 electrons in L shell).
(e) Carbon has twice as many electrons in its second shell as in its first shell (2 electrons in K shell and 4 electrons in L shell).
Question 4:
(a) What property do all elements in the same column of the Periodic
Table as boron have in common?
(b) What property do all elements in the same column of the Periodic
Table as fluorine have in common?
(a) All the elements in the same column as boron have the same number of valence electrons (3). Hence, they all have valency equal to 3.
(b) All the elements in the same column as fluorine have the same number of valence electrons (7). Hence, they all have valency equal to 1.
Question 5:
An atom has electronic configuration 2, 8, 7.
(a) What
is the atomic number of this element?
(b) To which of the following elements would it be chemically
similar? (Atomic numbers are given in parentheses.)
N(7) F(9) P(15) Ar(18)
(a) The atomic number of this element is 17.
(b) It would be chemically similar to F(9) with configuration as 2, 7.
Question 6:
The position of
three elements A, B and C in the Periodic Table are shown below −
Group
16
|
Group
17
|
−
|
−
|
−
|
A
|
−
|
−
|
B
|
C
|
(a) State whether A
is a metal or non-metal.
(b) State whether C
is more reactive or less reactive than A.
(c) Will C be larger
or smaller in size than B?
(d) Which type of
ion, cation or anion, will be formed by element A?
(a) A is a non-metal.
(b) C is less reactive than A, as reactivity decreases down the group in halogens.
(c) C will be smaller in size than B as moving across a period, the nuclear charge increases and therefore, electrons come closer to the nucleus.
(d) A will form an anion as it accepts an electron to complete its octet.
Question 7:
Nitrogen
(atomic number 7) and phosphorus (atomic number 15) belong to group
15 of the Periodic Table. Write the electronic configuration of these
two elements. Which of these will be more electronegative? Why?
| Element | K L M |
| Nitrogen Phosphorus |
2 5 2 8 5 |
Question 8:
How does
the electronic configuration of an atom relate to its position in the
Modern Periodic Table?
In the modern periodic table, atoms with similar electronic configurations are placed in the same column. In a group, the number of valence electrons remains the same.
Elements across a period show an increase in the number of valence electrons.
Question 9:
In the
Modern Periodic Table, calcium (atomic number 20) is surrounded by
elements with atomic numbers 12, 19, 21, and 38. Which of these have
physical and chemical properties resembling calcium?
The element with atomic number 12 has same chemical properties as that of calcium. This is because both of them have same number of valence electrons (2).
Question 10:
Compare
and contrast the arrangement of elements in Mendeleev’s
periodic Table and the Modern Periodic Table.
Mendeleev’s
periodic table
|
Modern periodic
table
|
||
| 1. | Elements are arranged in the increasing order of their atomic masses. | 1. | Elements are arranged in the increasing order of their atomic numbers. |
| 2. | There are a total of 7 groups (columns) and 6 periods (rows). | 2. | There are a total of 18 groups (columns) and 7 periods (rows). |
| 3. | Elements having similar properties were placed directly under one another. | 3. | Elements having the same valence shell are present in the same period while elements having the same number of valence electrons are present in the same group. |
| 4. | The position of hydrogen could not be explained. | 4. | Hydrogen is placed above alkali metals. |
| 5. | No distinguishing positions for metals and non-metals. | 5. | Metals are present at the left hand side of the periodic table whereas non-metals are present at the right hand side. |