Positive Ions (AQA GCSE Physics)
Revision Note
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 Tips and Tricks
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.
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