Important Questions (1 Mark): Periodic Classification of Elements

# Important Questions (1 Mark): Periodic Classification of Elements - Class 10

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## 21 Questions MCQ Test Science Class 10 - Important Questions (1 Mark): Periodic Classification of Elements

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Important Questions (1 Mark): Periodic Classification of Elements - Question 1

### The nuclear charge of Li is:

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 1
As we know, an atomic number of Li is 3. So it contains 3 protons in the nucleus, So it nuclear charge is 3.

Important Questions (1 Mark): Periodic Classification of Elements - Question 2

### Which of the following is one of the major drawbacks of Mendeleev's periodic table?

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 2
Major Drawbacks of Mendeleev's Periodic Table
There are several major drawbacks associated with Mendeleev's periodic table, including:
1. Gaps left in the table:
- Mendeleev's periodic table had several gaps where elements were yet to be discovered.
- These gaps left uncertainty and made it difficult to predict the properties of missing elements.
2. Inaccurate placement of elements:
- Mendeleev's periodic table did not always accurately place elements based on their atomic masses.
- Some elements were placed in groups solely based on their chemical properties, even if their atomic masses did not fit the pattern.
3. Isotopes:
- Mendeleev's periodic table did not account for isotopes.
- Isotopes are atoms of the same element with different numbers of neutrons, resulting in different atomic masses.
- Since Mendeleev arranged elements based on atomic mass, the presence of isotopes would have disrupted the pattern in his table.
4. Lack of atomic number concept:
- Mendeleev's periodic table did not incorporate the concept of atomic number.
- Atomic number is the number of protons in an atom's nucleus and is now used to arrange elements in the modern periodic table.
- Arranging elements by atomic number provides a more accurate representation of element properties.
Conclusion:
While Mendeleev's periodic table was a significant step in organizing the elements, it had some major drawbacks. The gaps in the table, inaccurate placement of elements, failure to account for isotopes, and the absence of the atomic number concept were limitations that hindered its effectiveness. These drawbacks were addressed and improved upon in the development of the modern periodic table, which provides a more comprehensive and accurate representation of the elements and their properties.
Important Questions (1 Mark): Periodic Classification of Elements - Question 3

### With an increase in temperature by 10k ,the rate of reaction becomes double. How many times the rate of reaction will be, if the temperature is increased from 303 k to 353 k ?

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 3
Given information:
- The rate of reaction doubles with a temperature increase of 10K.
Calculations:
To find the increase in the rate of reaction with a temperature increase from 303K to 353K, we need to determine the difference in temperature and calculate the corresponding increase in the rate.
1. Difference in temperature:
- ΔT = final temperature - initial temperature
- ΔT = 353K - 303K
- ΔT = 50K
2. Increase in rate with a 10K temperature increase:
- Let's assume the initial rate of reaction is R.
- With a temperature increase of 10K, the rate becomes 2R.
- This means that for every 10K increase, the rate doubles.
3. Increase in rate with a 50K temperature increase:
- Since the rate doubles for every 10K increase, we can calculate the increase in rate with a 50K increase as follows:
- Increase in rate = (2^5)R
- Increase in rate = 32R
The rate of reaction will be 32 times the initial rate when the temperature is increased from 303K to 353K. Therefore, the correct answer is D: 32.
Important Questions (1 Mark): Periodic Classification of Elements - Question 4

Name the element that first shows some visible metallic properties at room temperature.

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 4
The high ionization energy makes the element appear non-metallic while Iodine and astatine having low ionization energy display metallic properties and Iodine was the first element to show some physical properties of metals.

Important Questions (1 Mark): Periodic Classification of Elements - Question 5

The properties of_________were predicted by Mendeleev before their isolation.

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 5
Mendeleev has the foresight to leave some gaps in the periodic table for 3 elements and these elements are discovered later and included in the table.

Important Questions (1 Mark): Periodic Classification of Elements - Question 6

The number of elements known in Mendeleev's presented periodic table is:

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 6
The number of elements known in Mendeleev's presented periodic table is:

Explanation:
- Dmitri Mendeleev presented the first periodic table in 1869.
- He arranged the elements in order of increasing atomic mass and grouped them based on their similar properties.
- At that time, Mendeleev's periodic table consisted of 63 known elements.
- The elements were organized into horizontal rows called periods and vertical columns called groups.
- Each element was assigned a unique atomic number, symbol, and atomic mass.
- Mendeleev's periodic table provided a systematic way to organize and predict the properties of elements.
- Over time, the periodic table has expanded as new elements have been discovered or synthesized.
- Currently, there are 118 known elements in the modern periodic table.
- However, at the time Mendeleev presented his periodic table, only 63 elements were known.
In summary:
- The number of elements known in Mendeleev's presented periodic table is 63.
Important Questions (1 Mark): Periodic Classification of Elements - Question 7

The law of triads is not applicable to:

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 7
The law of triads does not apply to Ru, Rh, Pt.

Important Questions (1 Mark): Periodic Classification of Elements - Question 8

Lanthanides belong to which period?

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 8
Lanthanides belong to 6th period.They start from atomic number 58 and ends in 71

Important Questions (1 Mark): Periodic Classification of Elements - Question 9

The elements in the_______group have________chemical properties.

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 9

All the elements of a group have similar chemical properties because they have same number of valence electrons in their outemost shell

Important Questions (1 Mark): Periodic Classification of Elements - Question 10

In Mendeleev's periodic table,the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.69 amu.Reason for the same is that:

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 10
According to Mendeleev's classification,the properties of elements are the periodic function of their atomic masses and there is a periodic recurrence of elements with similar physical and chemical properties.

Important Questions (1 Mark): Periodic Classification of Elements - Question 11

The law of triads was given by:

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 11

In the year 1829, Johann Wolfgang Dobereiner,a German scientist, was the first to classify elements into groups based on John Dalton's assertions. He grouped the elements with similar chemical properties into clusters of three called 'Triads'. The distinctive feature of a triad was the atomic mass of the middle element.When elements were arranged inorder of their increasing atomic mass,the atomic mass of the middle element was approximately the arithmetic mean of the other two elements of the triad.

Important Questions (1 Mark): Periodic Classification of Elements - Question 12

In order to fit elements into his table, Newlands adjusted two elements in the same slot, but also put some unlike elements in the same slot.

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 12

For example, cobalt and nickel were in the same slot and these were placed in the same column as fluorine, chlorine and bromine which have very different properties than these elements. Iron,which resembles cobalt and nickel in properties,had been placed far away from these elements.

Important Questions (1 Mark): Periodic Classification of Elements - Question 13

Mendeleev examined the relationship between_________and______for classification of elements.

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 13
Explanation:
Mendeleev examined the relationship between chemical properties and atomic masses for the classification of elements. This approach led to the development of the periodic table, which is still used today to organize and classify elements based on their properties and atomic masses.
Here is a detailed explanation of Mendeleev's examination:
1. Chemical properties:
- Mendeleev observed that elements with similar chemical properties tend to have similar atomic masses.
- He noted that elements with similar chemical properties often occur in groups or families within the periodic table.
- By comparing the chemical properties of different elements, Mendeleev was able to identify patterns and trends that helped him in the classification process.
2. Atomic masses:
- Mendeleev recognized that the atomic mass of an element plays a significant role in determining its properties and behavior.
- He arranged the elements in order of increasing atomic mass, starting with the lightest element (hydrogen) and progressing to the heaviest elements.
- Mendeleev noticed that elements with similar chemical properties tended to have atomic masses that increased in a regular pattern.
3. Classification of elements:
- By examining the relationship between chemical properties and atomic masses, Mendeleev was able to organize the elements into a periodic table.
- He arranged the elements in rows (periods) and columns (groups) based on their properties and atomic masses.
- Mendeleev left gaps in his periodic table for elements that were yet to be discovered, and he was able to predict the properties of these missing elements based on their position in the table.
In conclusion, Mendeleev's examination of the relationship between chemical properties and atomic masses was crucial in the development of the periodic table and the classification of elements. This approach allowed for the organization of elements based on their properties and provided a framework for further scientific discoveries in the field of chemistry.
Important Questions (1 Mark): Periodic Classification of Elements - Question 14

Pair of element shaving same number of valence electrons is:

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 14

To determine the pair of elements that have the same number of valence electrons, we need to consider the electron configuration of each element.
Valence Electrons:
Valence electrons are the electrons in the outermost shell of an atom. They are responsible for the chemical properties and reactivity of an element.
Element Options:
We have the following element options:
A: N, O
B: Na, Ca
C: As, Bi
D: Pb, Sb
Valence Electron Configuration:
To determine the number of valence electrons, we need to look at the electron configuration of each element.
A: N - 2s2 2p3 (5 valence electrons)
O - 2s2 2p4 (6 valence electrons)
B: Na - 3s1 (1 valence electron)
Ca - 4s2 (2 valence electrons)
C: As - 4s2 3d10 4p3 (5 valence electrons)
Bi - 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p3 (5 valence electrons)
D: Pb - 6s2 4f14 5d10 6p2 (4 valence electrons)
Sb - 5s2 4d10 5p3 (5 valence electrons)
Conclusion:
From the given options, the pair of elements that have the same number of valence electrons is C: As and Bi. Both As and Bi have 5 valence electrons.
Therefore, the correct answer is option C.
Important Questions (1 Mark): Periodic Classification of Elements - Question 15

How many periods were there in Mendeleev's periodic table?

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 15
Explanation:
To determine the number of periods in Mendeleev's periodic table, we need to understand what a period is in the context of the periodic table.
Definition:
A period in the periodic table is a horizontal row that represents the arrangement of elements according to their atomic number.
Details:
Mendeleev's periodic table was arranged based on the atomic number of elements and their chemical properties.
Here are the details regarding the number of periods in Mendeleev's periodic table:
1. Period 1:
- Consists of two elements: hydrogen (H) and helium (He).
2. Period 2:
- Consists of eight elements: lithium (Li), beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), and neon (Ne).
3. Period 3:
- Consists of eight elements: sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), and argon (Ar).
4. Period 4:
- Consists of eighteen elements: potassium (K), calcium (Ca), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), arsenic (As), selenium (Se), bromine (Br), and krypton (Kr).
5. Period 5:
- Consists of eighteen elements: rubidium (Rb), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), indium (In), tin (Sn), antimony (Sb), tellurium (Te), iodine (I), and xenon (Xe).
6. Period 6:
- Consists of thirty-two elements: cesium (Cs), barium (Ba), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), thallium (Tl), lead (Pb), bismuth (Bi), polonium (Po), astatine (At), and radon (Rn).
7. Period 7:
- Consists of thirty-two elements: francium (Fr), radium (Ra), act
Important Questions (1 Mark): Periodic Classification of Elements - Question 16

What were the limitations of Mendeleev's periodic table?

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 16
Limitations of Mendeleev's periodic table:
A. The position of Hydrogen was uncertain:
- Mendeleev placed hydrogen in a group with the alkali metals due to its similar chemical properties, but it also exhibited some similarities to the halogens.
- The position of hydrogen in the periodic table was uncertain because it did not fit neatly into any specific group or period.
B. There was no space for isotopes of elements:
- Isotopes are atoms of the same element with different numbers of neutrons.
- Mendeleev's periodic table did not account for isotopes as he arranged elements based on their atomic masses.
- Isotopes have the same atomic number but different atomic masses, so they should have been placed in separate positions on the periodic table, which was not possible in Mendeleev's table.
C. Atomic masses do not increase in a regular manner in going from one element to the next:
- Mendeleev organized elements in his periodic table based on increasing atomic masses.
- However, he encountered some irregularities where the atomic masses did not follow a consistent trend.
- For example, iodine (atomic mass 126.9) was placed before tellurium (atomic mass 127.6) even though iodine has a higher atomic mass.
D. All of the above:
- The limitations mentioned above collectively contributed to the shortcomings of Mendeleev's periodic table.
- These limitations were later addressed by advancements in atomic theory and the development of the modern periodic table.
Important Questions (1 Mark): Periodic Classification of Elements - Question 17

Law of Triad was proposed by

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 17
Law of Triad was proposed by Dobereiner.
Detailed
The Law of Triad was proposed by Johann Wolfgang Dobereiner, a German chemist, in the early 19th century. This law was one of the earliest attempts to organize the elements based on their chemical properties and atomic weights.
Key Points:
- The Law of Triad states that when elements are arranged in order of their increasing atomic weights, the middle element in a triad has properties that are an average of the other two elements.
- Dobereiner observed that certain groups of three elements showed similar chemical properties and their atomic weights had a specific relationship.
- One example of a triad is calcium (Ca), strontium (Sr), and barium (Ba). Calcium has an atomic weight of 40, strontium has an atomic weight of 88, and barium has an atomic weight of 137. The atomic weight of strontium is the average of calcium and barium. These elements also exhibit similar chemical properties.
- Dobereiner identified several other triads, such as chlorine (Cl), bromine (Br), and iodine (I), and lithium (Li), sodium (Na), and potassium (K).
- The Law of Triad provided the basis for the development of the periodic table by other chemists, such as Dmitri Mendeleev.
- However, the Law of Triad had limitations and was not applicable to all elements. It could only explain the properties of a few groups of elements.
Overall, Dobereiner's Law of Triad was an important early contribution to the understanding of the periodic table and the relationships between elements based on their atomic weights and chemical properties.
Important Questions (1 Mark): Periodic Classification of Elements - Question 18

Which of the following statements can help a chemistry student to predict chemical properties of an element?

(I) Position of element in the periodic table

(II) Atomic number of the element

(III) Number of shells in the atom

(IV) Number of electrons in the outermost shell.

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 18
To predict chemical properties of an element.

Important Questions (1 Mark): Periodic Classification of Elements - Question 19

If the two members of a Dobereiner triad are phosphorus and antimony, the third member of this triad is:

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 19
According to Dobereiner, the atomic mass of the middle element was nearly equal to the arithmetic mean of the other two.Therefore,the atomic mass of the third element is which is nearly equal to the atomic mass of arsenic.
Important Questions (1 Mark): Periodic Classification of Elements - Question 20

_________were not included in Mendeleev's periodic table.

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 20
There were many demerits in the Mendeleev periodic table,such as,isotopes were not included in his periodic table as the isotopes were discovered long after this discovery..

Important Questions (1 Mark): Periodic Classification of Elements - Question 21

Whose name is not associated with the development of periodic Table

Detailed Solution for Important Questions (1 Mark): Periodic Classification of Elements - Question 21
Whose name is not associated with the development of periodic Table?

The name that is not associated with the development of the periodic table is Rutherford.

#### Explanation:

• Prout's: William Prout, an English chemist, proposed the concept that all elements are made up of atoms and that the atomic weight of an element is a whole number multiple of the atomic weight of hydrogen. However, his ideas were not fully accepted and later experiments showed that his concept was not entirely accurate.

• Newlands: John Newlands, an English chemist, proposed the Law of Octaves in 1865. He arranged the known elements in order of increasing atomic weights and noticed that every eighth element had similar properties. Although his classification system was not widely accepted, it was a precursor to the modern periodic table.

• Rutherford: Ernest Rutherford, a New Zealand-born British physicist, is not associated with the development of the periodic table. He is well-known for his contributions to the understanding of the atom's structure, especially for his gold foil experiment which led to the discovery of the atomic nucleus.

• Lothar Meyer: Lothar Meyer, a German chemist, independently published a periodic table in 1869, around the same time as Dmitri Mendeleev. Meyer's table arranged the elements based on their atomic volumes, which is a precursor to the modern periodic table. However, his work did not gain as much recognition as Mendeleev's.

Therefore, the correct answer is C: Rutherford.

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