What does it mean if hydrogen ion concentration and hydroxide ion concentration are equal?

Write the symbol for every chemical element that has atomic number greater than 3 and atomic mass less than 12.0 u.

The human eye contains a molecule called 11-cis-retinal that changes shape when struck with light of sufficient energy. the change in shape triggers a series of events that results in an electrical signal being sent to the brain that results in vision. the minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kj/mol.

Which statement accurately represents the arrangement of electrons in bohr’s atomic model?