Carbon has two isotopes. The isotope carbon-13 has 6 protons plus 7 neutrons. Carbon-14 is the rarest isotope of carbon containing 8 neutrons. Some isotopes are unstable and their nucleus tends to lose subatomic particles forming an element with a lower atomic mass. This process is known as radioactive decay .
Metals are elements that usually conduct heat and electricity and are shiny.
Nonmetals do not conduct electricity that well and are normally not shiny. Metalloids have characteristics that are in between metals and nonmetals. Elements with a net positive or negative charge are called ions . Chemists indicate the number of positive or negative charges on an ion using a superscript after the element's symbol. Positive and negative ions are electrically attracted to each other.