Chapter 3 Matter in action

What are the three types of Change?

Transformation of matter Physical change: Does not change the type substance

Chemical change (chemical reaction) composition of a substance is altered

Signs of chemical change Change in colour (e.g iron rusting) Gas being released( baking soda and vinegar) Light or heat being given off Change in smell

Chemical Change Involve the electrons in the outermost shell The outermost electrons are called valence electrons

Nuclear change Occurs within the nucleus of the atom; the number of protons and neutrons changes

Bonds between atoms Bonded atoms are called molecules Same type of atom (O2)= element 2 or more different types of atoms = compound

Molecular formulas Write down the elemental symbols Use subscripts to indicate how many of each element after it’s symbol

Why do atoms react? Think electrons

How and why atoms react? Noble gases are most stable, do not react They have complete outer shells (8 valence electrons) All elements bond in order to resemble the nearest noble gas

Ionization The loss or gain of electrons

Ions- atoms that have lost or gained electrons Anions are negative Cl + 1e- → Cl- Cations are positive Ca → Ca2+ + 2e-

Finding Charge Protons are positive Electrons are negative Therefore subtract electrons from protons. examples

The Lewis Diagram

P.178 -179 #1 and #2

Examples

Ions with Lewis Dot

Chemical Bonds Covalent bonds Ionic bonds

Ionic bonds Electrons are “stolen” One atom takes the electrons and becomes negative One atom loses the electrons and becomes positive

Ionic Bonds Normally a combination of metals and non-metals. Who will gain? Halogens will gain, you are more likely to pick 1 electron than lose 7. Who will lose? Alkalies and alkaline earth metals. You are more likely to give up one or two electrons than gain 6 or 7.

P. 188 # 5-6-7

Charge associated with Ion Group IA has a charge of +1, because it will want to loose an electron. Group IIA has a charge of +2 it will want to give up two electrons Group IIIA has a charge of +3 Group VA will have a charge of ____________ Group VIA will have a charge of ___________ Group VIIA will have a charge of __________

Assign a charge to each of the following atoms O P B Br Na Cl Mg Al

The Crossover Rule Helps determine the molecular formula of ionic compounds Steps: Write element symbols with their ionic charges charges go to the bottom of the opposite element. (no sign on bottom)

P.188 #8 P.189 #9

Covalent bonds Electrons are shared between the 2 atoms Have structural formula

When and why? Elements that are far apart on the periodic table (non-metal and a metal) will bond ionically Elements that are close together on the periodic table will bond covalently. ( 2 non-metals)

P. 190 # 10-11

Or use Electronegativity Small number in right hand corner of periodic table Subtract the numbers for the two elements in the compound E.g. Na = 0.9, Cl = 3.0 3.0 – 0.9 = 2.1 1.7

P. 186 # 1-2 P 187 # 3-4

P.207 #1 to 4 P.208 #5 to 8

Molecular structure Only occur in Covalent bonds