ATOMS and ISOTOPES

Atoms and ions

atoms consist, at a basic level, of:

• a nucleus consisting of protons (positively charged) and neutrons (neutral)
• electrons (negatively charged), that surround the nucleus.

An ion is formed by loss or gain of electrons. The valence of the ion tells us how many electrons have been gained or lost

. i.e., Carbon: 6 protons and 6 electrons, looses 4 electrons to become the cation C 4+

The ATOMIC NUMBER = NUMBER OR PROTONS

The ATOMIC WEIGHT = TOTAL WEIGHT OF PROTONS AND NEUTRONS

Isotopes

• The atomic number tells us what the element is (i.e., identifies its place on the periodic table).

• The atomic weights of an element tells us which isotope we have!

For example:

Here are three isotopes of carbon (C).

The atomic number for C is 6, so that all carbon atoms have 6 protons.

C 12: 6 protons plus 6 neutrons

C 13: 6 protons plus 7 neutrons

C 14: 6 protons plus 8 neutrons

The C 14 ISOTOPE IS UNSTABLE and thus, undergoes radioactive decay!

The result of radioactive decay is that C 14 -> N 14, an isotope of nitrogen.