Chemical Bonding! Unit 6-3 Notes

I. Complete Valence Shell a. Families/Groups on the periodic table are organized by their valence electrons (the outer most electrons). Atoms will give, take, share electrons in order to make a full energy level

b. For the first 20 elements, each energy level/shell can hold a maximum amount of electrons. i. 1st Shell-can hold 2 electrons ii. 2nd Shell-can hold 8 electrons iii. 3rd Shell-can hold 8 electrons iv. 4th Shell can hold 8 electrons

c. Atoms want to have their energy levels completely full. d. Therefore, some atoms need to give away electrons to have all of their shells full and some atoms need to gain electrons to have their shells full.

II. Ions a. Ions are atoms with an electrical charge. i. When atoms lose an electron, they become positively charged. + ii. When atoms gain an electron, they become negatively charged. - b. This gain or loss of electrons causes atoms to go from being neutral to be charged (ions).

Example: Sodium c. Na is in group 1. -It has 1 valence electron. -It wants to have its last energy shell to have 8 electrons. -The easiest thing for Na to do is lose one electron. -When you lose a negative charge, you become positively charged because you have less electrons than protons.

III. Oxidation States Oxidation states explain how the atom usually reacts with other elements (if it will gain or lose electrons). A positive number means the atom wants to lose an electron because it has extra electrons. A negative number means the atom wants to gain an electron because it needs electrons.

IV. Chemical Reactions! A chemical reaction is a process in which new substances with new chemical and physical properties are formed. They happen when elements give, take or share electrons. c. Basically all chemical reactions happen because atoms are trying to complete their valence shells!

Chemical reactions happen when atoms give, take, or share electrons

The outer shells needs 8 electrons to be full. 11 p 12 n 17 p 18 n Na (sodium) has only 1 electron in the outer shell. Chlorine has 7 electrons in the outer shell. The outer shells needs 8 electrons to be full. If Na loses the one electron all of the other shells will be full and if Cl gains an electron all of its shells will be full. This is why these two elements bond together, they can help each other out!

17 + (protons) 18 – (electrons) Here, Cl has 17 protons and 17 electrons. Its overall charge is zero. If Cl gains an electron, it has: 17 + (protons) 18 – (electrons) This brings its charge to -1. So it has a negative charge which makes it an ion.

V. Chemical Bonding Chemical bonding is the combining of atoms to form molecules. After sharing or transferring electrons, atoms get “stuck” together a form a new substance. This is what forms compounds! i. Explains why Na can be stuck to Cl to make a harmless compound. + Sodium Chloride, or table salt, is a white solid. It dissolves easily in water and is safe to eat. Sodium is a soft, silvery white metal that reacts violently with water. Chlorine is a poisonous, greenish-yellow gas.

VI. Chemical Bonds When a chemical reaction happens, a chemical bond is formed! A chemical bond is the force of attraction that holds atoms together. Some chemical bonds are strong, and some are weak. The type of bond will depend on if electrons are given, shared or transferred.

VII. Ionic Bonds a. Ionic bonds form: i. When a metal and a nonmetal combine ii. When one atom TRANSFERS (gives) one or more electrons to another atom and it becomes an ION iii. One atom gains, another atom loses electrons Metals on the LEFT of periodic table LOSE electrons Nonmetals on the RIGHT of table GAIN electrons 1 Carbon & 2 Oxygen http://www.middleschoolchemistry.com/multimedia/chapter4/lesson5

Ionic Bonds Na has 1 valence electron Cl has 7 valence electron Now Na is happy because it has 8 electrons Now Cl is happy because it has 8 electrons

Since K gave up an electron, it is now a positive ion Since K gave up an electron, it is now a positive ion. Since S gained 2 electrons, it now has a -2 charge. K has 1 valence electron. Sulfur wants 2 more electrons to make 8. You need 2 of K to make sulfur happy.

Ca wants to give up 2 electrons so it can have 8 in its last shell. Cl wants one more electron to have a complete outer shell. It takes one calcium to satisfy 2 Cl to make this happen. Ca lost 2 electrons and is now positive +2. Cl gained an electron and is now -1.

VIII. Covalent Bonds a. Covalent bonds: It is between nonmetals and nonmetals. 1. Example-water (H20) Result in the SHARING of electrons. http://www.middleschoolchemistry.com/multimedia/chapter4/lesson4

Water forms a Covalent Bond

Example of Covalent Bonds - H has 1 valence electron and wants 1 more to have a complete shell of 2. - Carbon (Family 14) has 4 valence electrons and wants 4 more to make 8. - If they touch and SHARE electrons, then H is happy because it has 2 and C is happy because it has 8.

RECAP Ionic Covalent Who forms it? Electrons are being…

Nonmetals and nonmetals Summary Ionic Covalent Who forms it? Metals and Nonmetals Nonmetals and nonmetals Electrons are being… Transferred Shared

IX. Stable/Unstable Atoms a. Stable Atoms Atoms that have complete shells, like the Noble Gases, will not chemically react (bond) with anything. They will not give up electrons to become unstable, nor will they take electrons to create a new, unstable valence shell. b. Unstable Atoms Atoms that have incomplete valence shells are said to be unstable. They will do whatever necessary to complete their valence shells That means that they will give (transfer), take or share electrons with another atom so that their shell is complete

X. Chemical Equations Products Reactants Yields; produces Reactants-a substance that changes when it combines with another substance in a chemical reaction. Products-new compound that if formed after a chemical reaction Products Reactants Yields; produces

More about the equation… 1 1 Coefficient: the number that goes BEFORE the element or compound. It tells you the quantity of that substance. If no number is written, the coefficient is 1.

Counting Atoms! List the atoms & quantity C O C H Atom Quantity H Atom

Counting Atoms! List the atoms & quantity C O C H Atom Quantity 1 H 4 2 Atom Quantity H 4 O 2

Try these… CH4 Compound Total # of Atoms 4Al2Cl3 ___________________________

Try these… CH4 Compound Total # of Atoms 4Al2Cl3 ___________________________

Balanced or Unbalanced give examples to practice If a chemical reaction is balanced, then the number of atoms you started with will be the same as the number of atoms you ended with. Example- BALANCED 1 Carbon & 2 Oxygen + 4 Hydrogen & 2 Oxygen 1 Carbon 1 Carbon 4 Hydrogen 4 Hydrogen 4 Oxygen 4 Oxygen

More Examples… 1. Balanced or Unbalanced? 2. Balanced or Unbalanced? 4. 2Mg + 02  2MgO 5. H2 + S  H2S 1. Balanced or Unbalanced? 2. Balanced or Unbalanced? 3. Balanced or Unbalanced? 4. Balanced or Unbalanced? 5. Balanced or Unbalanced?