Question

the element that has the electronic configuration of $1s^2 2s^2 2p^6 3s^2 3p^6 4s^1$

1. co
2. ca
3. k
4. ar

Explanation:

Step1: Calculate total electrons

Sum the exponents in the electron configuration $1s^2 2s^2 2p^6 3s^2 3p^6 4s^1$. So, $2 + 2 + 6 + 2 + 6 + 1 = 19$.

Step2: Identify element by atomic number

The atomic number equals the number of electrons in a neutral atom. An atomic number of 19 corresponds to potassium (K). Now check the options:

• Co (Cobalt) has atomic number 27.
• Ca (Calcium) has atomic number 20.
• K (Potassium) has atomic number 19.
• Ar (Argon) has atomic number 18.

Answer:

1. K