Question

Complete the passage. K (potassium) belongs to group IA of the periodic table, and has 1 valence electron. Br (bromine) belongs to VIIA, and has valence electrons. answer= 7

Answer 1

Answer:

7

Explanation:

Answer 2

Answer:

See detailed explanation.

Explanation:

Hello.

In this case, since the electron configuration of potassium whose atomic number is 19 turns out:

$K^{19}: 1s^2,2s^2,2p^6,3s^2,3p^6,4s^1$

We can see that the last level is 4 which has one electron, meaning that potassium has one valence electron. Moreover, since bromine's atomic number is 35, its electron configuration is:

$Br^{35}: 1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,3d^{10},4p^5$

We can see that the last level is also 4 and it has 2+5 = 7 valence electrons. In such a way, we infer that the valence electrons are computed by the electrons at the outer or last energy level of an element.

Regards.