Questions: Which element has the following electron configuration: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 ? 1. Ca 2. Rb 3.5 n 4.5 r 5. None of these

Transcript text: Which element has the following electron configuration: $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2}$ $3 d^{10} 4 p^{6} 5 s^{2} ?$ 1. Ca 2. Rb $3.5 n$ $4.5 r$ 5. None of these

Solution

Solution Steps

Step 1: Identify the Electron Configuration

The given electron configuration is: \[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \, 3d^{10} \, 4p^6 \, 5s^2 \]

Step 2: Count the Total Number of Electrons

To determine the element, we need to count the total number of electrons in the configuration: \[ 2 (1s^2) + 2 (2s^2) + 6 (2p^6) + 2 (3s^2) + 6 (3p^6) + 2 (4s^2) + 10 (3d^{10}) + 6 (4p^6) + 2 (5s^2) = 38 \]

Step 3: Determine the Element

The atomic number of an element is equal to the number of electrons in a neutral atom. Therefore, the element with 38 electrons is Strontium (Sr).