Warm up:● Summarize 1.3 on the back of your

notes-make sure you answer the key questions.

Cool Chemistry Stuff:

Essential Question: How are chemicals the building blocks of life?

2.1 The Nature of Matter

Nature of MatterProtons, Neutrons and Electrons make up Atoms, the most basic unit of matter

Protons have a positive charge(proton, positive)

● Neutrons have a neutral charge○ neutron, neutral charge

Neutrons

● Have a negative charge(Ever wonder what caused electricity? Its electrons. Moving fast.)

Electrons (e-)

● Protons and neutrons make up the nucleus or center of the atom

● Electrons are in constant motion around the nucleus

Structure of Atom

● Protons and neutrons weigh about the same○ Example: If the nucleus weighs 10 amu (atomic

mass units) and there are 4 protons, how many neutrons are there?

Math (example in margin)

There are the same number of protons and electrons, thus making the atom neutral(the positive and negative charges cancel

out)

If the atom started off with4 electrons and he lost one,what is his charge?

How many protons does hehave?

More math...

● Element-a pure substance made up of only one type of atom (example: oxygen)○ Represented by one or two letter symbols

(example: O)○ Each element has its own Atomic Number-

the number of protons in a nucleus■ Example:An atom has 5 electrons, what is its

atomic number?

Elements

Isotopes● Atoms of the same element that:

○ have the same number of protons and electrons■ have similar chemical properties

○ differ in the number of neutrons● Radioactive isotopes have unstable nuclei

● Mass number-The total number of protons and neutrons in a nucleus○ Example: If a nucleus has 4 protons and 6

neutrons, what is its mass number?● Isotopes are identified by their mass

numbers

● Substances formed by 2 or more elements

● Chemical Formulas show the composition of a compound using the element’s symbols○ Example: Water’s chemical formula is H2O.

It is a compound made up of 2 hydrogen (H) atoms and 1 oxygen (O) atom

Compounds

The physical and chemical properties of a compound are usually different than its elements.

+ =

Hydrogen Gas Oxygen Gas WaterH2O

● Ionic bonds-formed when one or more electrons are transferred from one atom to the other○ Ions-atoms with an electric charge

■ Atoms that gain an electron are - charged (negatively)

■ Atoms that lose an electron are + charged (positively)

Ionic Bonds

Diagraming an ionic bond:

Sodium Metal + Chlorine Gas = Salt (SodiumChloride)

Again we see compounds are different than their elements...

● Covalent Bonds-Formed when electrons are shared between two atoms

●

Covalent Bonds

● the smallest unit of most compounds● Molecules are formed when atoms are

covalently bonded together

Molecules:

Water Molecule

● Van der Waals Forces-attraction between oppositely charged region of different molecules○ Electrons not shared equally in

covalent bonds b/w atoms○ Not strong○ The bigger the molecule the stronger

the force

FINALLY

Van der Waals Forces

1. Only draw energy levels of electrons2. Figure out how many electrons it has

(look at the atomic number)3. Put 2 electrons on the first energy level4. Put 8 electrons on all other energy levelsExample: Carbon, Atomic Number: 6

How to Draw a Bohr Diagram:

1. Write the elements symbol2. Look at which group it is in on the periodic table (only

the ones with A, so 1A, 2A etc)a. Whichever group it is in is the number of valence

electrons3. Pretend there is a box around the elements symbol.

Draw one electron on the top, side, bottom, other side (if the element has 4 or less electrons stop here)

4. If the element has 5 or more valence electrons, repeat step 3 so there are two electrons on each side of the box.

How to Draw a Lewis Diagram:

How to read the periodic table:

Practice problems:

Closure: