MCQ
An atom of an element has two electrons in the M shell. Identify its atomic number.
- A10
- B12
- C14
- D15
Explanation:
For M shell value of n = 3. Thus the electronic configuration is: 2, 8, 2 and atomic number is 12.
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[Given $pK _{ a }$ of $CH _{3} COOH =4.57$ ]

$A$. Atoms of all elements are composed of two fundamental particles.
$B$. The mass of the electron is $9.10939 \times 10^{-31} kg$.
$C$. All the isotopes of a given element show same chemical properties:
$D$. Protons and electrons are collectively known as nucleons.
$E$. Dalton's atomic theory, regarded the atom as an ultimate particles of matter Choose the correct answer from the options given below