Element with the electron configuration $1 s^2 2 s^2 2 p^6 3 s^2 3 p^5$ is
A. potassium
B. fluorine
C. sulfur
D. chlorine
E. carbon
Answer (1)
Count the total number of electrons: 2 + 2 + 6 + 2 + 5 = 17 .
Identify the element with atomic number 17.
The element with atomic number 17 is chlorine.
Therefore, the element is c h l or in e .
Explanation
Understanding the Problem We are given the electron configuration 1 s 2 2 s 2 2 p 6 3 s 2 3 p 5 and asked to identify the corresponding element from the given options.
Counting Electrons To identify the element, we need to count the total number of electrons in the given configuration. The number of electrons in each subshell is indicated by the superscript.
Total Number of Electrons The total number of electrons is 2 + 2 + 6 + 2 + 5 = 17 .
Identifying the Element The atomic number of an element is equal to the number of electrons in a neutral atom. Therefore, we need to find the element with an atomic number of 17.
Finding the Element on the Periodic Table Looking at the periodic table, the element with atomic number 17 is chlorine (Cl).
Final Answer Therefore, the element with the electron configuration 1 s 2 2 s 2 2 p 6 3 s 2 3 p 5 is chlorine.
Examples
Understanding electron configurations helps us predict how elements will interact to form chemical compounds. For example, knowing that chlorine has 7 valence electrons allows us to understand why it readily forms a bond with sodium, which has 1 valence electron, to create sodium chloride (table salt). This concept is fundamental in chemistry for predicting molecular structures and chemical reactions.
