Answer:
The mass number (A) of an atom is the total number of protons and neutrons in its nucleus. ... Because electrons have virtually no mass, just about all the mass of an atom is in its protons and neutrons. Therefore, the total number of protons and neutrons in an atom determines its mass in atomic mass units (Table 4.5. 1).
it might look like it has disappeared, but in fact it has just mixed with the water to make a transparent
Open systems are when matter and energy can freely move in and around the system. Closed Systems is when energy can freely move back and forth between the system but matter can not.
We can rewrite the equation KBr(aq) + AgNO3(aq) → AgBr(s) + KNO3(aq) into its net ionic equation into
K+ + Br- + Ag + + NO3- = AgBr + K + NO3-only aqueous solutions can dissociate. Spectator ions are present in both sides, hence these are K+ and NO3-. THe rules of assigning oxidation numbers is to identify the number of valence electrons of elements and may be arbitrary depending on the charge of the molecule.