REPRESENTING ATOMS

1. Atoms that are not bonded and stand alone are neutral. 2. That means in neutral atoms the number of protons are equal to the number electrons. This carbon atom is neutral because it has 6 protons and 6 electrons. The positive charge of the protons “cancel out” the negative charge of the electrons.

3. Only a certain number of electrons can fit in each electron shell (or level). Energy Level Electron Capacity

THE RULE OF OCTET Every atom tries to have 8 electrons in its outermost or valence shell. To accomplish this, atoms may need to give up, share, or take electrons. Noble gases have complete outer electron shells, which make them very stable. Other elements also seek stability, which governs their reactivity and bonding behavior. Halogens (group 17) are one electron away from filled energy levels. They each have 7 valence electrons so they are very reactive.

Alkali Metals (group 1) are very reactive metals that do not occur freely in nature. These metals have only 1 valance electron in their outer shell. Therefore, they are ready to lose that one valance electron in ionic bonding with other elements. Alkaline Earth Metals (group 2) are also reactive metals that do not occur freely in nature. These metals have 2 valance electrons in their outer shell.

4. The atomic number on the periodic table tells us how many protons each atom of the element has.

5. You can represent an atom by beginning with the atomic number. Let’s represent an Aluminum atom.

Aluminum Al To find the number of neutrons, subtract the atomic number from the atomic mass. For aluminum: = P 14 N

Now it’s your turn. Choose any four atoms from numbers 3 through 18 and complete your four diagrams.