Positive Ions
- Electrons in the outer energy level can be knocked out from an atom
- This can happen in a number of ways:
- When objects are rubbed together, electrons can be removed by friction
- When electrons absorb electromagnetic radiation they can gain enough energy to leave the atom
- From chemical reactions
- When one or more electrons are removed from an atom, it becomes positively charged
- This is because an electron is negatively charged
- The atom becomes a positive ion
- An ion is an atom or particle with a non-zero charge
When radiation passes close to atoms it can knock electrons out, leaving the atom with an overall positive charge
- Ions are more chemically reactive than atoms because of their positive charge
Examiner Tip
Definitions are very important for picking up marks on this topic. Be clear with your definitions such as ions and isotopes, and remember that ions have different numbers of electrons, whereas isotopes have different numbers of neutrons.
You met the idea of electron transfer in Static Electricity and Electric Charge. This is a good place to pause and explore any misconceptions that you might have. For objects or atoms to become charged, it is always the movement of electrons that causes it. Positive protons are locked away in the nucleus, so protons can't move around from atom to atom, but electrons can. Electrons are negatively charged. So if a neutral atom or object gains electrons, then it becomes more negative, it gains a negative charge (remember that when an atom gains a charge, we no longer call them atoms, we call them ions). In order for a neutral atom or object to gain a positive charge, it must lose electrons. The ion or object is left with more positive charge than negative, and so the overall charge of the ion or object is positive.
