Putting Atoms Together

Review:

Matter is divided into 2 main groups:

Pure Substances:◦Made of only 1 type of particle

Mixtures:◦Made of 2 or more types of particles

Mixtures can be divided further: Solutions:

◦Different components cannot be distinguished (they look like one substance)

Mechanical Mixtures:◦Individual

components can be seen, they do not mix together

Compounds:◦These are substances that contain two or more different elements, in fixed proportions.

Pure Substances can also be divided into:

Elements:◦Pure substances that cannot be broken

down into simpler substances.◦More importantly: They contain only one

type of atom!

Pure Substances can also be divided into:

Are the “building blocks” of all matter

Think of Lego: a small number of different blocks, but they can be combined to form anything you can think of!

Elements:

Elements are made of one type of atom.

Compounds are made of 2 or more elements.

Therefore: Compounds are made of TWO or MORE types of atoms.

Elements vs Compounds:

Determine which of the items in the list below are elements and which are compounds:

H2O CO2

Ar Ag

NaCl COO2

Try This:

A molecule is two or more atoms that are chemically joined together.

Molecules are defined by a chemical formula, which shows the number and type of each atom in a molecule.

Example: The chemical formula for water is H2O.

Molecules

Now determine which of the items in the list below are atoms and which are molecules:

H2O CO2

Ar Ag

NaCl COO2

Try This Again:

Can also be divided into 2 types:

Molecular Elements and Molecular Compounds

Molecular combinations involved non metals only.

Molecules (cont’d)

Let’s look at oxygen:

Like an oxygen atom, oxygen gas O2 (the stuff we breathe) is an element, because it has only one type of atom.

We call O2 a Molecular Element: a molecule made of atoms of the same element.

Molecular Elements

O2

O O

Elements that form molecules made of 2 atoms. We call these the diatomic molecules.

The seven diatomic molecules are:H2, O2, F2, Br2, I2, N2, Cl2

These elements are never found in nature as single atoms.

There are only Seven…

If you are having trouble remembering all of those, just remember:

HOFBrINCl it rhymes with Twinkle

An easy way to remember…

composed of more than one type of element.

Most molecules are molecular compounds.

From the chemical formula, we can determine how many atoms of each element are found in the molecule.

Molecular Compounds

chemical formula is H2O

The subscript “2” tells us there are 2 hydrogen atoms.

Because the oxygen does not have a subscript, it means there is only 1 oxygen atom.

Therefore, for every water molecule, we have 2 hydrogen atoms and 1 oxygen atom.

Example: Water

Water

H HO

Sugar has the chemical formula C6H12O6

From this formula, how many of each atom does sugar have?

Carbon atoms: Hydrogen atoms: Oxygen atoms:

Sugar

Sugar

Caffeine: C8H10N4O2

Capsaicin: C18H27NO3 (this is what makes food spicy)

Vinegar: C2H4O2

Some other Common Molecules:

Figure out the Total number of atoms of the following molecules:

H2SO4

CO2

NO3

KOHHClC5H5N5O

Try This:

Involve combinations between a metal and a non metal.

These compounds involve charged atoms called ions.

An ion forms when a neutral atom loses or gains electrons.

Ionic Compounds

When an atom loses electrons it becomes positive and is called a cation.

When an atom gains electrons is becomes negative and is a called an anion.

Examples: Aluminum Chloride (AlCl3)Sodium Sulfide (Na2S)

HomeworkPage 261, questions # 1, 2, 3, 4