Ch4. Mixtures, Elements, and Compounds

The facts that some do not understand!!!!

Some Ch4 topics that still confuse students.

1. What is the connection between atoms and elements?

2. What is the connection between atoms and molecules?

3. What is the connection between molecules and compounds?

What is the atom/element connection?

To answer this question we will discuss…….1. What an atom is made out of.2. How can atoms make elements.3. How can atoms make molecules.4. Molecules vs Compounds.

What is an atom made out of?

An atom is made by placing……• Protons in the center.

Without neutrons the center is unstable!!!

• Neutrons are added to the center for stability.

This center can now be called a nucleus!!!

• Around the nucleus there are orbits.

• Electrons are placed in orbits around the nucleus based on how many electrons are available. This atom has two negatives to match the two positives.

• We now have a working helium atom. ;)

+ +N

N

nucleus

-- --

How can atoms make elements?

• Now we will shrink the atom down to size.

• One atom is too small for our eyes to see, but if enough identical atoms are clumped together we can see the elemental clump.

1. Let us use the periodic table to build a Lithium atom.

2. 3 protons & 3 electrons

Round the Atomic mass #, then subtract the Atomic # to get 4 Neutrons.

3. Atoms, like the Lithium atom below, are too small to see with our eyes.

3

LiLithium6.941

+

++

+ NN

NN

N

E

E

E

E

+ ++

NN

NN

E

E

E

+++NNNNE

EE+++NN

NNE

EE

+++NNNNE

EE

+++NNNNE

EE

+++NNNNE

EE +++NN

NNE

EE

+++NNNNE

EE

+++NNNNE

EE

+++NNNNE

EE

+++NNNNE

EE

microscopic view

how we see it

Some Facts about Atoms

• Atoms are the smallest part of an element.

• Therefore the atom has the same properties as the element.

+++NNNNE

EE+++NN

NNE

EE

+++NNNNE

EE

+++NNNNE

EE

+++NNNNE

EE +++NN

NNE

EE

+++NNNNE

EE

+++NNNNE

EE

+++NNNNE

EE

+++NNNNE

EE made out of

+++NNNNE

EE

Elements are… identical atoms.

Atoms to Molecules • These atoms will join together, by sharing electrons, to form a molecule.

• To make this water molecule easier to represent, we can model it like this:

When atoms chemically combine they form a molecule.Below, is an oxygen atom & two hydrogen atoms.

Oxygen Atom

Two Hydrogen Atoms

E

+N +

N

E

NN+

N

NN

+ +N

N++

+

+

+N

E

E

E

E E

E E

E

NN+

N

NN

+ +N

N++

+

+

+N

E

E

E

E E

E E

E

+N

E

E

+N

SeparateAtoms

Molecule

Oxygen AtomHydrogen Atom Hydrogen Atom

NN+

N

NN

+ +N

N++

+

+

+N

E

E

E

E E

E E

E +N

E

E

+N

(A.K.A Water)

H

O

H

Some facts about Atoms becoming Molecules

• When different atoms join together to become a molecule

• The molecule behaves differently than the separate atoms ever did.

Oxygen AtomHydrogen Atom Hydrogen Atom

NN+

N

NN

+ +N

N++

+

+

+N

E

E

E

E E

E E

E+

N

E

E

+N

NN+

N

NN

+ +N

N++

+

+

+N

E

E

E

E E

E E

E +N

E

E

+N

H

O

H

H

O

H

Molecules vs CompoundsMolecules

• Molecules are made up of atoms that are chemically bonded.

• Once bonded into a molecule, the molecule behaves in a new way.

Compounds

• One molecule is too small for our eyes to see, but if enough identical molecules are clumped together we can see the group (now called a compound).

H H

O

H

O

HH

O

H

H

O

H

microscopic view

how we see it

H O

H

H

OH

H

OH

HO

H

H

OH

H

O

HH

OH

H

OH

HO

H

HO

H

HO

H

Facts about Molecules becoming Compounds

Since molecules are the smallest unit of a compound …

Whatever the compound can do the molecule can do!!!

H

O

H

H

OH

H

OH

H

O

H

H

OH

H

O

H

H

O

H

Compound

Molecule

Hope this helps. Good Luck!!