Atoms Ions and Isotopes Quick Review Atoms are

Atoms, Ions, and Isotopes

Quick Review • Atoms are made up of three particles: • Protons • Neutrons • Electrons • Question: Which of the three particles identifies what element an atom is? • The PROTON! (very important)

Different Forms of the Same Element • In any element, the # of protons is always constant. • Unlike the number of protons, the number of electrons and neutrons can vary within an element without changing the identity of the element. • Ex. Carbon (C) ALWAYS has 6 protons, but it can have anywhere from 6 -8 neutrons and 2 -10 electrons

Isotopes • An ISOTOPE is a form of an element that has a different number of neutrons than “normal” • The # of protons does NOT change! • Ex: • The most abundant Carbon has 6 protons, electrons and neutrons • So the atomic number is 12 • There is also Carbon 14 which still has 6 protons and electrons, but 8 neutrons • The atomic mass is now 14 because of the extra neutrons

Other Isotopes • Most atoms have naturally occurring isotopes including: • Radon • Potassium • Uranium • When an element is “radioactive” it means it has an unstable number of neutrons (an unstable ISOTOPE)

IONS • An atom usually has a neutral charge. That means it has the same number of protons as electrons • Remember, a proton has a positive charge and an electron has a negative charge • ION – an atom that has lost or gained one or more electrons and has become charged either positively or negatively

Positive Ions • When an atom LOSES electrons, it becomes more POSITIVE • Why? • If you are getting rid of negative particles (electrons) but your number of positive particles (protons) are staying the same. • In other words, you are subtracting negative numbers

Examples • What would the charge be if: • The neutral form of Gold (Au) lost 4 of its 79 electrons. It now has 79 protons and 75 electrons • The neutral form of Mg lost 2 of its 12 electrons. It now has 12 protons and 10 electrons.

Negative Ions • When an atom GAINS electrons it becomes more NEGATIVE • Why? • Electrons have a negative charge, so the more you have, the more negative you become

Representing Ions • Ions are represented by placing a “superscript” charge number next to the atomic symbol. • Ex. • O-2 = oxygen with a negative 2 charge • K+ = potassium with a positive 1 charge • N-3 = nitrogen with a negative 3 charge • And so on