An Arrhenius acid by definition dissociates in water to form H3O+ (or H+) ions while an arrhenius base dissociates in water to form OH- ions.
NH4+(aq) can be categorised as an arrhenius acid since it releases H3O+ ions in aqueous media
NH4+(aq) + H2O (aq) ↔ NH3 (aq) + H3O+(aq)
Answer: The element shown in the image is Helium (He).
Explanation: We are given a image of an atom having protons, neutrons and electrons.
Number of protons as shown in image = 2
Number of neutrons as shown in image = 2
Number of electron as shown in image = 2
Atomic number = Number of protons = Number of electrons
Atomic number of the element = 2
Atomic Mass = Number of protons + Number of neutrons
Atomic mass = 2 + 2 = 4
The element having Atomic number = 2 and mass number = 4 is Helium.
Element = 
All elements are made up of atoms. ➢ Atoms are made up of protons, neutrons, and electrons. Two different kinds of atoms can combine to form a compound. A molecule is a combination of atoms that cannot be broken apart while still retaining the same properties as the larger substance that it is a part of.