Post on 02-Jan-2016
Atoms are Lazy and Want to be Happy (Who doesn’t?)
• Atom’s goal is to fill its outer (valence) energy level
• ex. Cl (chlorine) has 7 electrons in its outermost energy level - it wants to gain one more to be happy (remember Octet rule?)
• Na (sodium) on the other hand, has 1 electron in its outermost energy level. It has a choice: gain 7 more electrons or lose 1.
Na will lose its lone electron and will become Na+
Cl will gain one electron (from sodium in this case) and become Cl-
NaCl, a neutral compound is formed!!!
Negative Charge
• If an atom gains an electron the atom becomes a negatively charged ion; written 1-
• Likewise, if an atom gains 2 electrons the atom becomes a doubly negative charged ion; written 2-
*This charged number is AKA oxidation number (the # of electrons an atom gains or loses when bonding)
chlorine atoms have: Positive Protons +17 Negative Electrons -17 Neutral Atom 0
If a chlorine atom gains an electron it becomes a negatively charged ion: Positive Protons +17 Negative Electrons -18 Negative Ion 1-
oxygen atoms have: Positive Protons +8 Negative Electrons -8 Neutral Atom 0
If an oxygen atom gains 2 electrons it becomes a negatively charged ion: Positive Protons +8 Negative Electrons -10 Negative Ion 2-
Positive Charge
• If an atom loses an electron the atom becomes a positively charged ion; written 1+
• Similarly, if an atom loses 2 electrons the atom becomes a doubly positive charged ion; written 2+
sodium atoms have: Positive Protons +11 Negative Electrons -11 Neutral Atom 0
If a sodium atom loses an electron it becomes a positively charged ion: Positive Protons +11 Negative Electrons -10 Positive Ion 1+
Neutral Compounds• Most compounds like NaCl are neutral
- or - they have no charge.
• Remember: Na+ + Cl- NaCl w/ no charge
• (+1) + (-1) = 0
• Sometimes more than one of the same
element can help to create a compound.
• If you know the the charges of the atoms you can determine how many atoms will be needed to create neutral compound.
• ex: if you know that Ti has a 3+ charge; when combined with Cl- in order to make a neutral compound you must have 3 Cl for every 1 Ti
• looks like this: TiCl3
(3+) + (1-) + (1-) + (1-) = 0 charge