Chemical Bonding! Mr. Coffey

Chemical Equations Reactants Products 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 1 H 4 2 Atom Quantity H 4 O 2

More Examples… 1. 2. 3. H S Hg Atom Quantity 4 O 3 Atom Quantity 9 O 4

Lewis Dot In 1916, Gilbert Lewis represented the valence electrons using dots. Electron dot diagrams are used to represent or show the valence electrons that an atom has.

X Lewis Structures Write the chemical symbol Use dots to show valence electrons (found by looking at the group number) They go in pairs around the “perimeter” of the imaginary box. This shows the general format of an electron dot diagram. The X shows any chemical symbol. X

Lewis Dot Structures by Family 1 2 13 14 15 16 17 18

A chemical reaction is a process in which new substances with new chemical and physical properties are formed. Why do they happen? Basically all chemical reactions happen because atoms are trying to complete their valence shell!

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

Complete Valence Shell? The outer most electrons are called valence electrons A complete valence shell has 8 valence electrons (if there is more than one energy level) Atoms will give, take, share electrons in order to make a full energy level

Energy Levels/Shells For the first 20 elements, each energy level/shell can hold a maximum amount of electrons. 1st Shell-can hold 2 electrons 2nd Shell-can hold 8 electrons 3rd Shell-can hold 8 electrons 4th Shell can hold 8 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!

Lewis Dot Structures by Family 1 2 13 14 15 16 17 18 With the Lewis Dot Diagram you can see which two elements would pair perfectly together.

Ions Ions are charged particles. When atoms lose an electron, they become positively charged. + When atoms gain an electron, they become negatively charged. - This gain or loss of electrons causes atoms to be charged (ions).

Here, Cl has 17 protons and 17 electrons. Its overall charge is zero. If Cl gains an electron, it has: 17 + 18 – This brings its charge to -1.

Oxidation States Oxidation states explain how the atom usually reacts with other elements. A positive number means the atom wants to lose an electron. A negative number means the atom wants to gain an electron.

Example: Sodium 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 positive.

+ Chemical Bonding When ATOMS get stuck together This is what forms compounds! 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.

Chemical Reactions When a chemical reaction happens, a chemical bond is formed! 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, taken….

What does it mean to be unstable? Atoms that have complete valence shells, like the Noble Gases, will not chemically react with anything. They will not give up electrons to become unstable, nor will they take electrons to create a new, unstable valence shell. 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/take or share electrons with another atom so that their shell is complete

Ionic Bonds Ionic bonds form: When a metal and a nonmetal combine When one atom TRANSFERS one or more electrons to another atom – it becomes an ION One atom gains, another atom loses 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.

Covalent Bonds Covalent bonds: Result in the SHARING of electrons. It is between nonmetals and nonmetals. http://www.middleschoolchemistry.com/multimedia/chapter4/lesson4

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.

Water forms a Covalent Bond

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

Atomic Structure Matters! The number of valence electrons that an atom has will determine how/if it will chemically react with other atoms. Remember how to find the number of valence electrons? FAMILY NUMBER!

ION vs. ISOTOPE An ion is a positive or negative atom that has more or less electrons. An ISOTOPE is an atom of the same element that has more or less neutrons. Having more or less neutrons can make an atom heavier or lighter. Being heavier or lighter will cause the atom to have sometimes new, special properties even though it is the same element

ISOTOPES Carbon typically has 6 neutrons so it is considered Carbon 12. If carbon has more neutrons it can become Carbon 14 which is a radioactive material!