WARM UPThe atomic mass of an element and the mass number of an atom often have similar values. However, atomic mass and mass number are not the same thing. Explain the difference.

WARM UPAcids and bases are two kinds of chemical compounds. Compare and contrast at least four chemical and physical properties of acids and bases.

WARM UPWhy don’t the noble gases in Group 18 on the periodic table form chemical bonds?

WARM UPYou measured the mass of a steel pipe before leaving it outdoors. One month later, the pipe had rusted, and its mass had increased. Does this change violate the law of conservation of mass? Explain your answer.

CHEMICAL BONDINGChapter 12

CHEMICAL BONDING A chemical bond is an interaction that holds two atoms

together. This joining of two atoms is called chemical bonding Atoms bond by sharing, gaining, or losing electrons Most atoms bond using only their electrons in the outermost

energy level. The electrons in the outermost energy level are called valence electrons

Sodium Atom

OCTET RULE The number of valence electrons determines whether an atom

will form bonds.

The outermost energy level of an atom is considered to be full if it contains 8 electrons. Hydrogen and Helium only need 2 valence electrons for a full

energy level.How many valence electrons are in the fluorine atom?

IONIC BONDS

Ionic bonds form when electrons are transferred from one atom to another Ionic bonds form between metals and nonmetals

COVALENT BONDS

Covalent bonds are formed when two atoms share one or more pairs of electrons Covalent bonds form between 2 nonmetals

http://www.youtube.com/watch?v=QqjcCvzWwww

METALLIC BONDS Metallic bonds are formed by the attraction between positive

metal ions and the electrons in the metal Electrons are not shared by adjacent atoms (atoms that are next to

each other), but are free to “roam” This gives metals their ability to conduct electricity

CHEMICAL REACTIONSChapter 13

SPI 0807.9.10 Identify the reactants and products of a chemical reaction

SPI 0807.9.11 Recognize that in a chemical reaction the mass of the reactants is equal to the mass of the products (Law of Conservation of Mass)

NEW SUBSTANCES

A chemical reaction is a process where one or more substances change to form one or more new substances

During a reaction, bonds are broken, atoms are rearranged, and new bonds are formed

Some signs of chemical reactions:Gas formationSolid formation (also called precipitate)Energy change (light, heat, electricity)Color change

http://www.youtube.com/watch?v=qx5lhj5grts

CHEMICAL FORMULAS

A chemical formula is a shorthand way to use chemical symbols and numbers to represent a substanceCarbon dioxide = CO2 Glucose = C6H12O6

The subscript number tells you how many atoms of an element are in the compound

CHEMICAL FORMULAS

Reading check: What is the difference between CO and Co?

Subscripts – the number of atoms

No number is understood to be “1”

Coefficients – the number of molecules

3H2SO4 =

H2SO4

H2SO4

H2SO4

6 – H, 3 – S, 12 - 9

H2SO4 =

2 – hydrogen

1 – Sulfur

4 – Oxygen

coefficient

subscript

CHEMICAL EQUATIONS A chemical equation uses chemical symbols and formulas as a

shortcut to describe a chemical reaction The starting materials in a reaction are reactants The substances formed from a reaction are products

C + O2 CO2

What are the reactants and products of the following equation?2H2 + O2 2H2O

The formulas of the reactants are written before the arrow

The formulas of the products are written after the arrow

The arrow, also called the yields sign, separates the reactants from the products

LAW OF CONSERVATION OF MASS

Law of Conservation of Mass states that mass is neither created nor destroyed in ordinary chemical and physical changes.

This means that a chemical equation must show the same numbers and kinds of atoms on BOTH sides of the arrow!

LAW OF CONSERVATION OF MASS

Which chemical equation best shows the law of conservation of mass?

A. 3Al + 2CuO Al2O3 + 2Cu

B. 2Al + 3CuO Al2O3 + 3Cu