Question

The first electron configuration quantum number describes

Answer 1

Answer: The correct answer is Option a.

Explanation:

There are four Quantum numbers. They are:

• Principle Quantum Numbers: It helps us to determine the size of the orbital and the energy level. It is represented by n. Where, n = 1,2,3,4....
• Azimuthal Quantum Number: It helps us to determine the shape of the orbital. It is represented as 'l'. The value of l ranges from 0 to (n-1). For l = 0,1,2,3... the orbitals are s, p, d, f...
• Magnetic Quantum Number: It helps us to determine the orientation of the orbitals. It is represented by the symbol $m_l$. The value of this quantum number ranges from $(-l\text{ to }+l)$. When l = 2, the value of $m_l$ will be -2, -1, 0, +1, +2.
• Spin Quantum number: It helps us to determine the direction of electron spin. This is represented as $m_s$ The value of this is $+\frac{1}{2}$ for upward spin and $-\frac{1}{2}$ for downward spin.

The first number in the electron configuration determines the energy level or electron shell of an atom. The number represents 'n' which is principle quantum number.

For Example:

Let us take an electronic configuration of $2s^1$

• $n=2$       (The electron is present in 2nd shell)
• $l=0$         (The orbital is 's'-orbital)
• $m_l=0$     (The value of l = 0 )
• $m_s=+\frac{1}{2}$     (Sign convention of spin quantum number)

Hence, the correct answer is Option a.

Answer 2

Answer : The correct option is, (a) the energy level.

Explanation :

As we know that there are four quantum numbers :

• Principle Quantum Numbers : It describes the size of the orbital and the energy level. It is represented by n. Where, n = 1,2,3,4....
• Azimuthal Quantum Number : It describes the shape of the orbital. It is represented as 'l'. The value of l ranges from 0 to (n-1). For l = 0,1,2,3... the orbitals are s, p, d, f...
• Magnetic Quantum Number : It describes the orientation of the orbitals. It is represented as $m_l$. The value of this quantum number ranges from $(-l\text{ to }+l)$. When l = 2, the value of $m_l$ will be -2, -1, 0, +1, +2.
• Spin Quantum number : It describes the direction of electron spin. This is represented as $m_s$ The value of this is $+\frac{1}{2}$ for upward spin and $-\frac{1}{2}$ for downward spin.

The first electron configuration quantum number describes the electron shell or the energy level of an atom. The value of 'n' ranges from 1 to the shell containing the outermost electron of that atom.

For example :

For $1s^1$ :

$n=1$       (Because it is in 1st shell)

$l=0$         (Because it is in 's' orbital)

$m_l=0$     (Because l = 0)

$m_s=+\frac{1}{2}$     (Because of the sign convention)

Hence, the correct option is, (a) the energy level.