Question

1. an atom of a certain element has the electron configuration of ar4s2 3d10 4p5. how many valence electrons does this element have? 7 10 17 2 5 option 7 clear selection 5) what is the element described in question #4? cl br se zn

Explanation:

Step1: Identify valence - shell electrons

Valence electrons are in the outermost shell. For the electron - configuration [Ar]4s23d104p5, the outermost shell is the 4th shell with electrons in 4s and 4p orbitals.

Step2: Calculate number of valence electrons

The number of electrons in 4s is 2 and in 4p is 5. So, the total number of valence electrons is 2 + 5=7.

Step3: Determine the element

Argon (Ar) has 18 electrons. Adding the electrons in the outer - shell (2 in 4s, 10 in 3d, and 5 in 4p), we have 18+2 + 10+5=35 electrons. The element with 35 electrons is Bromine (Br).

Answer:

1. A. 7
2. B. Br