Explain how a neutral atom can become

positively or negatively charged.

If a neutral atom gains electron it becomes negatively charged and if it loses electrons it becomes positively charged

Neutral atoms can be turned into positively charged ions by removing one or more electrons ... Atoms that gain extra electrons become negatively charged. A neutral chlorine atom, for example, contains 17 protons and 17 electrons. By adding one more electron we get a negatively charged Cl - ion with a net charge of - 1.