Compare and contrast the arrangement of elements in Mendeléev’s Periodic Table and the Modern Periodic Table.
Mendeleev’s periodic table |
Modern |
---|---|
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. |
(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?
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?
How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
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?
How could the Modern Periodic Table remove various anomalies of Mendeléev’s Periodic Table?
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) AI (d) Si
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
In the Modern Periodic Table, which are the metals among the first ten elements?
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?
Use Mendeléev’s Periodic Table to predict the formulae for the oxides of the following elements:
K, C, AI, Si, Ba.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
What would you observe when zinc is added to a solution of iron(II) sulphate? Write the chemical reaction that takes place.
What are the different ways in which individuals with a particular trait may increase in a population?
Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) → 2Pb(s) + CO2(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and c
(iv) all
Explain the terms analogous and homologous organs with examples.
What is the function of digestive enzymes?
What are the changes seen in girls at the time of puberty?
Why is variation beneficial to the species but not necessarily for the individual?
Why is the use of iodised salt advisable?