Question

how an atom become positive and negative​

Answer 1

Answer:

Unlike protons, electrons can move from atom to atom. If an atom has an equal number of protons and electrons, its net charge is 0. If it gains an extra electron, it becomes negatively charged and is known as an anion. If it loses an electron, it becomes positively charged and is known as a cation.

Answer 2

an atom is electrically neutral.

but it can become positive by loosing an electron and become negative by gaining an electron because an electron is negatively charged.