The Class 10 is an important year in a student’s life and Maharashtra State Board Science 1 is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 10 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 10 Science 1 Book syllabus.
1. Write down the electronic configuration of the 3 Li, 14 Si, 2 He, 11 Na, 15 P from the given atomic numbers. Which of these elements belongs to the period 3? Answer with explanation.
Ans: The electronic configuration of these elements are as given below:
Electronic configuration of Li is 1s2 2s1
That of Si is 1s2 2s2 2p6 3s2 3p2
Electronic configuration for He = 1s2
Electronic Configuration of Na is 1s2 2s2 2p6 3s1
That of P is 1s2 2s2 2p6 3s2 3p3
From this it is seen that elements Na, Si and P have the same value as the principle quantum number of the outermost shell.
2. Write the name and symbol of the elements from the given descriptions:
(a) The atom having the smallest size
(b) The most electronegative atom
(c) The most reactive non-metal
Answer: (a) Hydrogen is the element with symbol H that has the smallest atom
(b) Fluorine with F symbol is the most electronegative atom
(c) Fluorine with F symbol is also the most reactive non-metal
3. Write short notes on Mendeleev’s periodic law.
Answer: The periodic table was organised by Mendeleev according to the chemical and physical properties of the elements. These were the molecular formula of the hydrides and oxides of the elements, melting points, boiling points and densities of the elements and their hydrides and oxides. Mendeleev determined that the elements with similar physical and chemical properties repeat after a definite interval. So, as per this finding he stated the following periodic law that properties of elements are periodic functions of their atomic masses. The vertical columns in the Mendeleev’s periodic table are the groups while the horizontal rows are known as periods.
4. Point out the merits of mendeleev’s periodic table.
Answer: Mendeleev takes into consideration the basic property of elements, namely, the atomic mass, as standard and arranged 63 elements known at that time in an increasing order of their atomic masses. Then, he transformed this into the periodic table of elements in accordance with the physical and chemical properties of these elements. On the basis of the law that the properties of elements are a periodic function of their atomic masses, to all the known elements, Mendeleev arranged the elements, keeping in mind that the information available till then was not final and it could change. Following this, Mendeleev’s periodic table is said to have the following merits.
1. In order to give the atoms proper place in the periodic table as per their properties, the atomic masses of some elements were revised. For example, the previously determined atomic mass of beryllium, 14.09, was modified to the correct value 9.4, and beryllium was placed before boron.
2. Mendeleev’s periodic table has vacant places to accommodate the elements that are not discovered yet. Three of these unknown elements were eka-boron, eka-aluminium and eka-silicon from the known neighbours with atomic masses 44, 68 and 72, respectively. Not only this, but their properties were also predicted. Later on, these elements were discovered and named as scandium (Sc), gallium (Ga) and germanium (Ge) respectively. The properties of these elements matched well with those predicted by Mendeleev. Due to this success, all were convinced about the importance of Mendeleev’s periodic table and this method of classification of elements was accepted immediately.
3. Meanwhile, Mendeleev ’s periodic table did not have a place to include the noble gases like helium, neon or argon. But, later, in the 19th century, when they were discovered, Mendeleev created the zero group where the noble gases fitted very well without any disturbance to the original periodic table.
5. The third period contains only eight elements, even though the electron capacity of the third shell is 18. Why?
Answer: The third period contains only eight elements, even though the electron capacity of the third shell is 18 because after 8 electrons go to the third shell, the next one is added to the fourth shell. Actually, the 3rd shell should contain 18 elements, but as per Aufbau ’s principle, electrons should be filled in the abilities according to their increasing order of energies. It is seen that 4s orbital has lower energy than 3d orbital i.e the electrons fill in this order 3s <3p <4s <3d. So, 8 electrons fill the 3s and 3p orbitals then fill the orbital in the 4th shell. So, of the 18 electrons, there are 10 electrons which are found to have a high energy equivalent to the energy of the 4th shell. Hence, these electrons are not counted in the 3rd shell and only 8 electrons are in the 3rd shell, resulting in the 2, 8, 8, 18, electronic configuration.
6. Write the name of the family of metals having valency one and two.
Answer: Alkali metals are the family of metals having valency one, while Alkaline earth metals have valency two.
7. What are Dobereiner ’s Triads?
Answer: Dobereiner identified that properties of elements and atomic masses are related. He manufactured groups of three elements, each with similar chemical properties and naming them triads. He arranged the three elements in a triad as per the increasing order of atomic mass and showed that the atomic mass of the middle element was approximately equal to the mean of the atomic masses of the other two elements.
8. What are the limitations to Newland’s Octaves?
Answer: Newlands’ octaves have many limitations. They are as follows:
9. Position of hydrogen, according to mendeleev’s periodic table.
Answer: Hydrogen has properties similar with halogens (group VII). That is, the molecular formula of hydrogen is H₂ while the molecular formulas of fluorine and chlorine are F2 and Cl2 , respectively. Meanwhile, the chemical properties of hydrogen and alkali metals (group I) are similar, also a similarity is found in the molecular formulae of the compounds of hydrogen alkali metals (Na, K, etc) formed with chlorine and oxygen. From these observations, it is not possible to decide whether the correct position of hydrogen is in the group of alkali metals (group I) or in the group of halogens (group VII).
10. What is a modern periodic table?
Answer: A modern periodic table is the classification of elements resulting from an arrangement of the elements in an increasing order of their atomic numbers. The properties of elements can now be identified more accurately with the help of the modern periodic table. This table was manufactured on the basis of atomic numbers. The modern periodic table is also called the long form of the periodic table. In the modern periodic table the elements are arranged in accordance with their atomic number.
Meanwhile, the students are recommended to go through all the topics thoroughly. The best resources that the students can find to prepare more effectively for the Maharashtra State Board exam includes the textbooks, question papers, syllabus and so on.