5
atomic number
Electrons in the outermost energy shell (valence shell) have the most energy.
5
Electrons in the outermost shell are called valence electrons.
If "penultimate" means "next-to-outermost", the correct answer is 8: The innermost shell is full with two 1s electrons; the next-to-outermost shell is full with two 2s electrons and six 2p electrons, for a total of 8. The outermost shell has five valence electrons, constituting with the two inner shells the remainder of the proper number of total electrons for phosphorus, 15, its atomic number.
atomic number
Electrons in the outermost energy shell (valence shell) have the most energy.
5
On the outermost (or valence) electron shell.
Electrons in the outermost shell are called valence electrons.
I think it's the valence shell
Valence.
If "penultimate" means "next-to-outermost", the correct answer is 8: The innermost shell is full with two 1s electrons; the next-to-outermost shell is full with two 2s electrons and six 2p electrons, for a total of 8. The outermost shell has five valence electrons, constituting with the two inner shells the remainder of the proper number of total electrons for phosphorus, 15, its atomic number.
An octet of electrons is when the outermost electron shell of an atom contains eight electrons.
The valence shell is the outermost electron shell containing electrons.
seven
6