§2.4 The structure of atoms

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§2.4 structure of atoms

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What is a carbon atom made of?

What do the solar system and an atom have  in common?

Let's go back in time

to 1808...

John Dalton 

thought.....

Thompson thought differently

In 1904 he proposed

A ball with small charged balls within it. 

Rutherford thought.

The nucleus

Protons     Neutrons

and 

The electron cloud

Niels Bohr made a small correction

There is no such thing as an electron "cloud"! The electrons are located within layers!

Every element in the periodic table has a unique amount of protons

Atomic model by Bohr

A substance is made up of molecules.

Molecules are made up of atoms.

An atom is made up of:

• a nucleus containing protons and neutrons
• electrons in orbits around the nucleus

Take notes

Information about an atom in the periodic table

Atomic number equals:

• number of protons
• number of electron

Carbon has 6 protons and 6 electrons.

And oxygen has ... ?

Isotopes

Isotopes are different types of the same atom.

Hydrogen can have

1 proton, 1 electron and 1 neutron

OR

1, proton, 1 electron and 2 neutrons 

The Isotopes of Hydrogen

Same amount of protons and electrons

so it behaves the same. 

it is just has more mass when it has an extra neutron.

Protons and neutrons determine the mass of an atom

elektrons are SO LIGHT, that the do not influence mass

The number of protons within an atom is equal to its Atomic number

Information about an atom in the periodic table

Atoms can also be represented differently, as C-12 or as the figure below

12 indicates the atomic mass

6 indicates the atomic number

C is the symbol 

The atomic number = number of protons = number of electrons

The mass number    = number of protons + number of neutrons

Carbon has 12 - 6 = 6 neutrons

(the number of protons does not have to be equal to the number of neutrons!)

What is a carbon atom made of?

In the nucleus of an atom you can find?

1. electrons and neutrons
2. electrons and protons
3. neutrons and protons
4. electrons, protons and neutrons

The total mass of protons and neutrons is the atomic mass.

The atomic number of an atom tells you?

1. The number of electrons in an atom.
2. The number of neutrons in an atom.
3. The number of protons in an atom.
4. Nothing.

Back to work!

- TEST NEXT WEEK!! Questions????

Homework:

52, 55, 59, 60, 63, 64, 69, 70