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 d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

Most of the radio active elements are present in__________

  1. Lanthanoids

  2. Actinoids

  3. Representative elements

  4. Second transition series
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The actinoids are radioactive elements and the earlier members have relatively long half-lives.

The most common and known element is Uranium, which is used as nuclear fuel when its converted into plutonium, through a nuclear reaction.

Option B is correct.
Multiple choice chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

If the seventh period is completed, the atomic number of the last element would be:

  1. $118$
  2. $112$
  3. $107$
  4. $120$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As the seventh period will be completely filled its electronic configuration must be in the manner of noble gas configuration i.e., $ns^2,: np^6$ because the last element in every period is noble gas element. Hence, the electronic configuration of last element of seventh period is (Rn) $5f^{14} 6d^{10} 7s^27p^6$ as the electronic configuration contains $118$ electrons, the last element in the seventh period will have the atomic number $118$.

Multiple choice chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

Stable electronic configuration of a transition metal is:

  1. $1s^{2} 2s^{2}2p^{6} 3s^{2} 3p^{6} 3d^{9} 4s^{2}$
  2. $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{5}$
  3. $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2}$
  4. $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{10} 4p^{6}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Generally the elements having  half filled and completely filled outer electronic configurations are stable  elements,here in given options the configuration $1s^22s^22p^63s^23p^64s^23d^5$ contains half filled outer electronic configuration $(3d^5)$.


Hence option B is correct.

Multiple choice chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

The element with $Z = 106$ belongs to :

  1. $3^{rd}$ period
  2. $ 5^{th}$ period
  3. $7^{th}$ period
  4. $6^{th}$ period
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Z=106$ is seaborgium and its electronic configaration is $(Rn) 5f^{14}6d^{4}7s^{2}$. as the differenting electron enter into $7s$, 7 is the principle quantum number which represents the number of period to which the element belongs hence, the element belongs to 7th period.

Multiple choice chemistry d- and f-block elements actinoids the actinoids the d-and f-block elements comparison of lanthanoids and actinoids

An atom of element has $2K, 8L$ and $3M$ electrons. Then the element belongs to :

  1. IA group

  2. IIA group

  3. IIIA group

  4. IVA group
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The total number of electrons present in all the shells are $2+8+3=13$, hence the atomic number of element is $13$ and the electronic configuration would be $1s^22s^22p^63s^23p^1 $. Element belongs to $|||A$ group.

Multiple choice chemistry materials liquid crystals liquid state the liquid state

Most elements are solids at 25$^o$C and 1 atm pressure, the exception being the 11 elements that are gases and 2 that are liquids. What 2 elements are liquids?

  1. Hg and Br

  2. Hg and I

  3. Ag and Kr

  4. Au and Kr

  5. Pt and Co
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At room temperature, that is $25^o C$ and $1$atm, Mercury and Bromine both exist as liquids. Hence option A gives the correct pair.

Iodine, Silver, Platinum, Cobalt are all solid at room temperature. Whereas, Krypton is a gas at room temperature.                                            

Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

Which of the following lists contains ONLY heavy elements

  1. Oxygen, Carbon, Iron

  2. Helium, Oxygen, Carbon

  3. Hydrogen, Helium, Carbon

  4. Iron, Hydrogen, Oxygen
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Helium and hydrogen being lighter gases are seen in other options other than option a. Thus , such options are incorrect options

Multiple choice maths numbers and place value many forms of ten thousand standard form of numbers number names, numerals and place values

Charge of an electron is $0.00000000000000000016$ coulomb. This number can also be written in standard form as:

  1. $\displaystyle 1\cdot 6\times 10^{19}$
  2. $\displaystyle 1\cdot 6\times 10^{-20}$
  3. $\displaystyle 1\cdot 6\times 10^{-19}$
  4. $\displaystyle 1\cdot 6\times 10^{18}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$0.0000000000000000000016=\displaystyle \frac{16}{100000000000000000000}$


=$\displaystyle \frac{1\cdot 6\times 10^{1}}{10^{20}}$

=$\displaystyle 1\cdot 6\times 10^{-19}$

Multiple choice chemistry enthalpy changes enthalpy changes and enthalpy profile diagrams enthalpy study of enthalpy

the $\triangle { H } _{ 1 }\quad $ and $\triangle { H } _{ 2 }\quad $ $(in kJ mol^-1)$ and the $\triangle {egH } $  $(in kJ mol^-1)$ of a few 3 elements are given below:
Which of the element is likel;y to be:

Elements $\triangle { H } _{ 1 }\quad $ $\triangle { H } _{ 2 }\quad $  $\triangle {egH } $
I 520 7300 -60
II 419 3051 -48
III 1681 3374 -328
IV 1008 1846 -295
V 2372 5251 +48
VI 738 1451 -40

  1. the least reactive element

  2. the most reactive mental

  3. the most reactive non- mental

  4. the least reactive non-mental
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Element V has a positive electron gain enthalpy (+48 kJ/mol), meaning it requires energy input to gain an electron. This makes it the least reactive as it resists electron gain. Element II (ΔH1=419, ΔH2=3051, ΔegH=-48) would be most reactive metal, and Element III (ΔH1=1681, ΔH2=3374, ΔegH=-328) would be most reactive non-metal.