Atoms are composed of a positively charged nucleus and negatively charged electrons. These positive and negative charges cancel each other out, making each atom electrically neutral as a whole.
An ion is an atom that has had one electron taken away or added. This makes an electrically neutral atom into an ion with a positive or a negative charge. Different types of rays discovered during the 19th century, such as X-rays and uranium rays, have what is called an ionization power. This means that when they pass through matter, they can pull an electron out of the atoms they encounter. In doing so, they transform atoms into ions.
