Q1. Mendeleev’s predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
(i) Name the elements which have taken the place of these elements.
(ii) Mention the group and the period of these elements in the modern periodic table.
(iii) Classify these elements as metals, non-metals or metalloids.
(iv) How many valence electrons are present in each one of them?
Q2. What is meant by group in the modern periodic table? How do the following changes occur on moving from top to bottom in a group?
- Number of valence electrons
- Number of occupied shells
- Size of atoms
- Metallic character of element
- Effective nuclear charge experienced by valence electrons
Q3. Consider two elements A (atomic number = 17) and B (atomic number= 19)
- Write the positions of these elements in the modern periodic table giving justification.
- Write the formula of the compound formed when A combines with B.
- Draw the electron dot structure of the compound and state the nature of the bond formed between the two elements.
Q4. An element is placed in 2nd group and 3rd period of the periodic Table, burns in presence of oxygen to form a basic oxide.
- Write the electronic configuration.
- Write a balanced equation when it burns in the presence of air.
- Write a balanced equation when this oxide is dissolved in water.
- Draw the electron dot structure for the formation of this oxide. \
- Identify the element.
Q5. (i) Why do we classify elements?
(ii) What are the two criteria used in the development of Modern Periodic Table?
(iii) State the position of
(a) metals,
(b) non-metals and
(c) metalloids in the periodic table.
(iv) Would you place two isotopes of chlorine; Cl-35 and Cl-37 in different slots of the periodic table because of their different atomic masses or in the same slot because their chemical properties are same? Justify your answer.
Q6. (a) Why did Mendeleev have gaps in his periodic table?
(b) State any three limitations of Mendeleev’s classification?
(c )How do electronic configurations of atoms change in a period with an increase in atomic number?
Q7. (a) What was the basis of Mendeleev’s classification of elements?
(b) List two achievements of Mendeleev’s Periodic table.
(c) List any two observations which posed a challenge to Mendeleev’s Periodic Law.
Q8. (a) The modern periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. List one advantage and one limitation of all the three attempts.
(b) Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.
Q9. Explain giving justification the trends in the following properties of elements, on moving from left to right in a period, in the Modern Periodic Table:
(a) Variation of valency.
(b) Change of atomic radius.
(c) Metallic to non-metallic character.
(d) Electronegative character.
(e) Nature of oxides.
Q10. (a) An element which is an essential constituent of all organic compounds belongs to which group?
- Account for the following:
- Elements of group 18 are called zero-valent.
- If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride?
- An element X forms a chloride with formula XCI3. The element X would most likely be in the same group of the periodic table as for which of the following
- Na, Mg, AI or Ca.
- Elements of which groups will form acidic oxides?
Q11. (a) Consider the following elements:
Na (11), AI (13), Cl (17), K (19)
For the given elements, find out
(i) valency (ii) period number (iii) group number
(b) An element X belongs to group 17 and element Y belongs to group 1. What type of bond will they form?
Q11. The positions of five elements in the periodic table are shown below:
Group 1 | Group 2 | Group 15 | Group 16 | |
Period 1 | A | B | ||
Period 3 | C | D | E |
What are the number of valence electrons in B? Identify the element(s) which
(i) will have the. smallest atomic radius?
(ii) will be the most metallic?
(iii) will form basic oxide?
(iv) will show valency three?
(v) will show greatest tendency to gain electron?
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