An atom has the following electron configuration.

1s22s22p63s23p3

How many valence electrons does this atom have?

3
5
8
15

5 electrons

Explanation:

Valence electrons are electrons located in the outermost energy shell, so you want to count the number of electrons in the last energy shell.

You can divide the configuration into 1s2 / 2s22p6 / 3s23p3 to see the energy shells in this atom. There are 3 shells occupied by the atom's electrons, so you need to count the electrons in the third shell as those are its valence electrons.

2 + 3 = 5 valence electrons total

Note: you don't count the 3 before the letter because that only indicates the shell level, not the number of electrons. Count only the exponents.

- "the choice that is not an indicator of a chemical change is "state of matter changes". more common than not, chemical reactions produce energy in the form of light or heat. along with energy, they also produce a new substance called the product that could be in any state of matter (solid, gas, or liquid)."

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).