Tag: dobereiner's triads

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

An element $X$ belongs to fourth period and fifteenth group of the periodic table. Which of the following statements is true?

  1. It has a completely filled s-orbital and a partially filled d-orbital.

  2. It has completely filled s-and p-orbitals and a partially filled d-orbital.

  3. It has completely filled s-and p-orbitals and a half-filled d-orbital.

  4. It has a half-filled p-orbital and completely filled s-and d-orbitals.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Group 15 has a valence shell electronic configuration of $ns^2np^5$ and period $=4$$ means its $n=4$

thus electronic configuration of element $X$  is $4s^24p^3$

Elements of Group 15 and period 2 onwards are: $N, P, As, Sb, Bi$

Thus $X$ is Arsenic ($As$) and has electronic configuration of: $1s^22s^22p^63s^23p^63d^{10}4s^24p^3$. 

Thus, $s$ and $d-$orbitals are fully-filled and $p-$orbital is half-filled.

Hence, the correct option is $\text{D}$
Multiple choice chemistry the periodic table dobereiner's triads development of the modern periodic table into the history

Which of the following is an artificial element made by man?

  1. Gallium

  2. Iron

  3. Helium

  4. Americium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
In chemistry, a synthetic element is a chemical element that does not occur naturally on Earth, and can only be created artificially. So far, 24 synthetic elements have been created (those with atomic numbers 95–118). Americium is one of them having atomic no. 95.

Hence, the answer is option $D$.