Charge

Electronegativity

Electronegativity is the ability of each element to attract electrons.  If there is an uneven electronegativity among atoms in a molecule, the electrons are shared unevenly. This creates different types of bonds:

• Ionic: Generally a metal bonded to a nonmetal

• Covalent: Generally nonmetals bonded with each other

• Metallic: Generally metals bonded with each other

To determine the bond type, look at the difference in electronegativities from the periodic table then consult the chart (electronegativity is a periodic trend):

Ionic Bonds

Electrons are the part of the atom nearest its outer regions and are constantly moving around in electron clouds. Because of this the electrons in the outermost energy level of an atom does all of the bonding! This can be done by having atoms gain electrons, lose electrons, or share electrons. 

(Nearly all) Atoms prefer having 8 electrons in their highest energy level and want to get the same amount of electrons as noble gases. This is known as the Octet Rule. For ions, this is represented by atoms combining to gain a net neutral charge of 0, mixing cations and anions together to make compounds. Electrons in ionic bonds are transferred from the cations to the anions. Ionic compounds are called salts (Not to be confused with table salt, which is a type of salt). They are crystalline at room temperature, have high melting and boiling points, are soluble in water, and conduct electricity when dissolved (but not when in solid form).

Since electrons are negatively charged, gaining electrons makes a net negative charge and losing electrons makes a net positive charge. Metals usually form positive ions, known as cations (cats have paws so cations are pawsitive!). Nonmetals usually form negative ions, known as anions (a negative ion). To write the symbol for an ion you add the charge to the top right of the element's symbol (and don’t write a 1 if the charge is plus or minus 1), with the number before the sign. For example:

Ions and Orbitals

An orbital is a region within an atom where there is a probability of finding an electron (essentially one piece of the larger electron cloud). Orbital shapes are defined as the surface that contains 90% of the total electron probability. Orbitals are the reason that the periodic table has those specific blocks to it:

Electrons fill in this way because it's the way they can be as close to an atom's nucleus as possible without being close to one another. The electrons in the outermost orbital region of an atom are known as valence electrons and are the electrons that do all of the bonding for an atom. Within each part of an orbital there are 2 electrons (one to spin clockwise and one to spin counterclockwise). 

If we need to talk about a specific electron we can denote its name based on the orbitals within it. For example, 1s^1 would be the first electron that all elements would have (the one closest to the nucleus), 1s^2 is the second, 2s^1 is the third,  2s^2 is the fourth, 2p^1 is the fifth, and so on.

Additional Resources

• List of Common Ions

• Periodic Table of Ions (More Complete Chart)

Interesting Links

• Ionic Crystal Compounds  

• Something Weird Happens when you Simulate Lifeless Molecules