Question

(c.6b) neils bohr published his model of the atomic structure in 1913. he introduced the theory of electrons traveling in orbits around the atoms nucleus, with electrons orbiting only in certain orbits called shells. each shell can contain a fixed number of electrons. according to this model of the atom, the chemical properties of an element are mainly determined by the number of electrons in the outer shell. the total number of electrons in all shells. the number of electrons in the inner shells. the difference between number of electrons and protons

Explanation:

In Bohr's atomic model, chemical properties of an element relate to how atoms interact (bonding, reactions), which is driven by the electrons in the outermost shell (valence electrons). Inner shell electrons are stable, total electrons or electron - proton difference don't directly determine chemical behavior as outer - shell electrons do (they participate in bonding).

Answer:

the number of electrons in the outer shell.