Final answer:
True statements about electron configurations include that they describe the energy and likely location of electrons and help explain an atom's reactivity. It is possible to determine the number of valence electrons from the electron configuration.
Step-by-step explanation:
The statements that are true about electron configurations are:
- (A) The electron configuration of an atom describes the energy of electrons in the atom.
- (B) The electron configuration for an atom describes the likely location of electrons in that atom.
- (C) The electron configuration of an atom is a tool we can use to explain the reactivity of an atom.
Statement D is incorrect. We can indeed determine the number of valence electrons an atom has using an electron configuration diagram or notation by looking at the number of electrons in the outermost shell. The electron configuration is key to understanding the chemical behavior of an element as it provides critical information about the arrangement of electrons in shells and subshells which influence bonding and reactivity.