Lesson: Periodic Classification of Elements
Which of the following statements is
not a correct statement about the trends when going from left to right across
the periods of the 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)
Element X forms a chloride with the
formula , 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) AI
(d) Si
(b)
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
(b) Magnesium
(c) Silicon
(d) Boron
(e) Carbon
(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)
Valency equal to 3.
(b)
Valency equal to 1.
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) 17.
(b) Fluorine (F) with the configuration as 2, 7
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. Therefore, electrons come
closer to the nucleus.
(d) A will form an anion as it accepts an
electron to complete its octet.
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?
Nitrogen (7): 2, 5
Phosphorus (15): 2, 8, 5
Since, electronegativity decreases with moving from top to bottom in a
group, nitrogen will be more electronegative.
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.
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?
Both calcium and the elements with atomic number 12
and 38 have same number of valence electrons, i.e. 2. Hence both these elements
have the same properties.
Compare and contrast the arrangement of
elements in Mendeleev’s Periodic Table
and the Modern Periodic Table.
Mendeleev's Periodic Table |
Modern Periodic Table |
Elements are arranged in the increasing order of
their atomic masses. |
Elements are arranged in the increasing order of
their atomic numbers. |
There are 8 Groups. |
There are 18 Groups. |
Groups are subdivided into sub-groups. |
Groups are not subdivided into sub-groups. |
Groups for noble gases were not present. |
A separate group is meant for noble gases. |
Position of isotopes could not be explained by
Mendeleev’s periodic table. |
Position of isotopes is well explained. |