Chemistry

Periodic Classification and Elements

1,176 Questions

Periodic classification organizes chemical elements based on atomic structure, periodic laws, and elemental properties. It covers historical classification systems, electron configurations, and periodic trends. Test takers preparing for chemistry sections will find these questions crucial for mastering fundamental element properties and atomic interactions.

Periodic table structureAtomic orbitalsElement identificationPeriodic laws

Periodic Classification and Elements Questions

Multiple choice chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

If $N _A$ is the Avogadro's number then number of valence electrons in 4.8 g of $O^{2-} $ is:

  1. $2.4\, N _A$
  2. $4.2\, N _A$
  3. $1.6\, N _A$
  4. $3.2\, N _A$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Number of mole in 4.8 gm of oxygen atom $=\dfrac{4.8}{16} = 0.3$ mole 

Number of the valence electron in one ion of $O^{2-} = 8$

Number of the valence electron in 0.3 mole of $O^{2-} = 8\times0.3\times N _A =2.4N _A$

Hence, the correct option is $(A)$.
Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

According to the law of triads :

  1. the properties of the middle element were in between those of the other two members.

  2. three elements arranged according to increasing weights have similar properties.

  3. the elements can be grouped in the groups of six elements.

  4. every third element resembles the first element in periodic table.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Dobereiner's law of triads, the properties of the middle element were in between those of the other two members. The elements were arranged in a group of three (called triads). The atomic weight of a middle element was almost the average of the other two. Three elements of the triad had similar chemical properties.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Which of the following elements follow Dobereiner's law of Triads?

  1. Na = $23$, Li = $7$ and K = $39$
  2. Cl = $35$, Br = $80$ and F = $19$
  3. Ca = $40$, Mg = $24$ and Sr = $88$
  4. Na = $23$, K = $39$ and Rb = $85$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Dobereiner's, the atomic weight of the middle element is nearly the same as the average of the atomic weights of the other two elements.


$Li(7)+K(39)\longrightarrow \cfrac{7+39}{2}=Na(23)$

So, $Na=23, Li=7$ and $K=39$ 

The correct option is ( A ) 

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

In the Doberiener's triad, all three elements have similar:

  1. electronic configuration

  2. properties

  3. number of shells

  4. both A and B
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the Doberiener's triad, all three elements have similar properties and the atomic weight of the middle member of each triad is very close to the arithmetic mean (average) of the other two elements.


The Dobereiner's triads include (1) Li, Na, K (2) Ca, Sr, Ba and (3) Cl, Br, I.

Hence, the correct option is $\text{B}$

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Dobereiner was the first person to illustrate the relationship between the ____________ of elements and their properties.

  1. atomic masses

  2. electron negativity

  3. molecular masses

  4. number of protons
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Dobereiner grouped elements in set of triads. Thus each group had 3 elements. Dobereiner classified elements into groups based on their properties. He illustrate the relationship between the atomic masses of elements and their properties with his law of triads.

Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Electronic configuration of silver atom in ground state.

  1. $\left[ Kr \right] { 3d }^{ 10 }{ 4s }^{ 1 }$
  2. $\left[ Xe \right] { 4f }^{ 14 }{ 5d }^{ 10 }{ 6s }^{ 1 }$
  3. $\left[ Kr \right] { 4d }^{ 10 }{ 5s }^{ 1 }$
  4. $\left[ Kr \right] { 4d }^{ 9 }{ 5s }^{ 2 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The electronic configuration of $Ag$ in ground state is:$[Kr]4d^{10}5s^1$