Atomic Number = number of protons In atom Structure of Atoms Atomic Number = number of protons In atom Atomic Mass = mass of protons, neutrons and electrons in atom

Structure of Atoms Isotopes – alternative forms of an atom that differ in their number of neutrons How are these atoms different from each other? What can isotopes be used for?

Do Now – 10-11-12 What does group number tell us? How many valence electrons does Neon have? What do you think an ionic compound is?

Bonding and Compounds Ionic Covalent

Structure of Atoms Atoms contain protons, neutrons, and electrons. Protons - positive charge – 1 atomic mass unit Neutrons – no charge – 1 atomic mass unit Electrons – negative charge – almost no mass

Structure of Atoms

Structure of Atoms There are certain spaces around the nucleus where electrons are likely to be found. The electron is found a certain distance from the nucleus called a shell. Within a shell is an orbital that holds 2 electrons.

The outermost electron shell is referred to as the valence shell. Structure of Atoms The outermost electron shell is referred to as the valence shell.

Structure of Atoms RULES ABOUT ELECTRONS! 1. First energy shell can contain a maximum of 2 electrons 2. All other shells can contain a maximum of 8 electrons (there are exceptions) An atom is most stable when the valence shell contains a full 8 electrons = OCTET RULE

Electrons determine chemical reactivity. Structure of Atoms RULES ABOUT ELECTRONS! Electrons determine chemical reactivity. Atoms are reactive unless they have a full valence shell of electrons!

Ions An atom or group of atoms that has a net positive or negative charge *Remember – During a chemical reaction, the proton number stays the same, but electrons may be lost or gained. Cation – An ion with a net positive charge, caused by the loss of one or more electrons Anion – An ion with a net negative charge, caused by an increase in the number of electrons.

Do Now – 10-12-12 Which atoms on the periodic table have a full valence shell? Which atoms on the periodic table have only one electron in the valence shell? Which atoms on the periodic table have seven electrons in the valence shell?

# of valence electrons = = the electrons in the outermost shell/energy level Use the periodic table to figure out the number of valence electrons Rule: # of valence electrons = group #

Valence Electrons 1 8 DON’T FOLLOW RULE 2 2 2 3 3 4 4 4 5 5 6 6 7 7

Lewis Dot Diagrams Why show only valence electrons? = model that shows the valence electrons of an atom Why show only valence electrons? They are the electrons that elements use to form compounds.

Lewis Dot Diagrams Rule 1: Fill dots in counter clockwise Rule 2: Write 4 dots individually, then pair them with a second dot

Lewis Dot Diagrams for Period 2 Li Be B C N O F Ne # of Val. e- =

So what’s going to happen if an atoms valence shell is not full? Ionic Bond – Bond between 2 ions

Patterns If an atom has 3 valence electrons, is it shorter to give up 3 or gain 5? What charge would it become? If an atom has 5 valence electrons, is it shorter to gain 3 or give up 5? What charge would it become?

Do Now – 10-15-12 If an atom has 5 valence electrons, will it gain or lose electrons? What will it’s overall charge be? Predict what charge Al will carry as an ion.

Predictions Atoms Want a full outer shell, so they take the easiest route to getting it. By gaining or losing electrons. This allows us to predict an ions charge. Remember atoms in the same group have the same number of? So, atoms in the same group react the same.

Ionic Charge +1 DON’T FOLLOW RULE +2 +3 4 ±4 --3 -2 -1

Electronegativity is the tendency of an atom to attract electrons. Chapter 2 Chemical Principles Bonding Electronegativity is the tendency of an atom to attract electrons. If the electronegativity of an atom is high, then it attracts and holds on to electrons. If the electronegativity of an atom is low, then it tends to give electrons away.

Bonding Where on the Periodic Table do you find the atoms with high electronegativity? Where do you find those atoms with low electronegativity? Which atom has the highest electronegativity? Using ionization energies explain why metals lose electrons more easily than nonmetals.

Why form chemical bonds? Elements are more stable when they have a full outer energy level The stable number of electrons in the outer shell is 8

Where do they get the electrons to fill their outer shell? From other atoms -by giving or stealing electrons from other atoms OR -By sharing their electrons with other atoms

Atoms and bonding Chemical bond = an attractive force that holds atoms or ions together All elements with unfilled outer energy levels (containing less than 8 valence electrons) can form bonds

Bonding Ionic bonding – Atoms transfer or accept electrons from one another Look at the following diagram with regards to sodium (Na) and chloride (Cl) What must each do to fulfill the octet rule?

Bonding Ionic bonding The sodium ion and the chloride ion will be attracted to each other and form an ionic bond. Na + Cl - The ionic bond is due to the attractive forces between the now positively charged sodium & the negatively charged chloride. By looking at the periodic table, can you predict which atoms may form ionic bonds?

Ionic Compounds A substance containing ions that can conduct an electric current when dissolved Compounds formed between a metal and nonmetal (ions) Charge of Cations + Charge of Anions = net charge of zero

Ionic Compounds - Compound made up of positive ions and negative ions Most are: Solids arranged in a repeating, 3D structure = crystal lattice Conduct electricity when dissolved in water or melted - +

BONDING Bonding IONIC BONDING COVALENT BONDING non-polar covalent and Chapter 2 Chemical Principles Bonding BONDING IONIC BONDING COVALENT BONDING non-polar covalent and polar covalent

Bonding Based on their chemical formulas, which of these compounds is not an ionic compound? KBr O2 SO2 FeCl3 CH4

Non-polar covalent bond – equal sharing of electrons Bonding Covalent bonding Non-polar covalent bond – equal sharing of electrons Polar covalent bond – unequal sharing of electrons What does the word polar mean?

H C Covalent bonding Bonding How many electrons are needed to fill the valence shell of carbon? How many electrons are needed to fill the valence shell of hydrogen? In the molecule of methane (CH4), the electrons are shared equally between the carbon and hydrogens.

Bonding Covalent bonding

Bonding Covalent bonding

Bonding Covalent bonding

Molecules A neutral group of atoms that are joined together by one or more covalent bonds. The attraction between the shared electrons and the protons in each nucleus hold the atoms together in covalent bond. Diatomic Molecules – typically nonmetals; two atoms bonded together covalently H2 F2 N2 O2 Cl2 Br2 I2 (4/7 are halogens)

Polar covalent bond – unequal sharing of electrons Bonding Covalent bonding Polar covalent bond – unequal sharing of electrons A great example of a molecule with polar covalent bonds is water. Why is water considered polar? What is a partial positive and partial negative charge?

Bonding Covalent bonding Polar covalent bond

Non polar bonding Example: CO2

Hydrogen bond A polar covalent bond involving Hydrogen with any of the three most electronegative elements of Nitrogen, Oxygen and Fluorine is especially strong and is called a Hydrogen bond.

Bonding Isomers These are molecules with the same number and type of atoms but with different orientations in space.

Questions Based on their electron dot configurations what is the formula for the covalently bonded compound of nitrogen and hydrogen? What happens to the charge on atoms when they form a polar covalent bond? Name the two factors that determine whether a molecule is polar?

End here

Bonding Covalent bonding Polar covalent bond

Water is the solvent of Life! Properties of Water Water Water is the solvent of Life! Solute – substance dissolved in a solvent to form a solution Solvent – fluid that dissolves solutes

Properties of Water Water Hydrogen bonds make water cohesive and give water surface tension. You can experience surface tension when you do your dishes.

Water Properties of Water Because water has both adhesive and cohesive properties, capillary action is present. Capillary action is one of the major reasons that trees and other plants can grow very tall.

In order to raise the temperature of water, the average molecular speed has to increase. It takes much more energy to raise the temperature of water compared to other solvents because hydrogen bonds hold the water molecules together! Water has a high heat capacity. Properties of Water Water Water is cooling! Do I look cool?

Water Properties of Water Water is less dense as a solid! This is because the hydrogen bonds are stable in ice – each molecule of water is bound to four of it’s neighbors.

Water Properties of Water So can you name all of the properties of water? Adhesion Cohesion capillary action high surface tension holds heat to regulate temperature (High heat capacity) less dense as a solid than a liquid