Chapter 4 - H

Atoms

4.1 Journal – Using Analogies

The network of blood vessels in your body is like the network of streets and highways in a large city. How are the two networks similar? Both networks are used to transport objects from one location to another. The comparison is an example of an analogy. An analogy uses a similarity to compare two objects or systems. A familiar object is often used to help explain a less familiar object. 1.

Atoms in compounds are like bricks in a wall. Explain this analogy. 2.

3.

Think of and explain another analogy for atoms in compounds.

WORK ON THE “ATOMIC MATH” WORKSHEET.

4.1 Studying Atoms

ANCIENT GREEKS 

DEMOCRITUS:



“atomos” = indivisible, uncut



Different types of atoms with specific properties



ARISTOTLE:

 

Only 4 elements No limit to divisions

4.1 Studying Atoms

DALTON’S ATOMIC THEORY:

particles that cannot be divided all matter is made of

Evidence: 

Compounds have fixed compositions H2O 2g H always combines with 8g O 4g H always combines with 16g O

4.1 Studying Atoms

DALTON’S ATOMIC THEORY:

particles that cannot be divided all matter is made of

 MAIN POINTS: 1) All matter is made of atoms. Atoms are indivisible and indestructible.

2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms.

H2O, CO2, CH4, H2SO4 4) A chemical reaction is a

rearrangement

of atoms.

4.1 Studying Atoms

DALTON’S ATOMIC THEORY:

4.1 Studying Atoms

THOMSON’S ATOMIC THEORY:

particles that CAN be divided matter is made of

 EVIDENCE:  Conducted a current thru a tube

4.1 Studying Atoms

THOMSON’S ATOMIC THEORY:

of particles that CAN be divided all matter is made

 EVIDENCE:   No matter what metal was used, the particles had a mass 1/2000 of a Hydrogen atom.

The beam was always attracted to the positive side

Hypothesis- these particles came from the atoms.

4.1 Studying Atoms - Thomson’s “plum pudding” Model

The 'Plum Pudding' Model of an Atom

4.1 Studying Atoms

RUTHERFORD’S ATOMIC THEORY:

positive charge is concentrated in the nucleus all atoms

4.1 Studying Atoms

RUTHERFORD’S ATOMIC THEORY:

positive charge is concentrated in the nucleus all atoms

Discovered: 

Uranium emits fast moving positive particles

Hypothesis:  

If you shoot positive particles at gold foil (other atoms), what would happen to the particle?

Their path will not change (according to Thomson’s plum pudding)

4.1

Studying Atoms – Gold Foil Experiment

4.1 The Gold Foil Experiment

RUTHERFORD’S ATOMIC THEORY

all atoms positive charge is concentrated in the nucleus

4.1

Studying Atoms – Modern Atomic Theory

Bohr Atom:

focused on the electrons

 Electrons are in energy levels  They move when the atom gains or loses energy

4.2/4.3 The Structure of the Atom & Modern Atomic Theory

1.

JOURNAL:

Work on the “Bohr Model” Worksheet from the back table. Use the Periodic Table to help you.

FILL IN THE Parts of an ATOM: Subatomic particles – distinguished by mass, charge and location

Subatomic particle PROPERTIES



Protons (p+):

   

In the nucleus Charge of 1+ Mass of 1 DEFINES THE ELEMENT (equals the ATOMIC NUMBER)

Protons (p+):



Atoms of DIFFERENT elements have DIFFERENT numbers of protons

Subatomic particle PROPERTIES

  

Neutrons (n

°

): In the nucleus NO charge

 

Mass of 1 Protons + neutrons = the ATOMIC MASS

Neutrons (n

°

):



Atoms of the same element with DIFFERENT numbers of neutrons are called

ISOTOPES

 

Neutrons (n

°

): ISOTOPES of Hydrogen. Same Atomic #, different Mass #

Electrons (e-):

    

In ENERGY LEVELS around the nucleus Charge of 1 Mass of 1/1836 of a p+ Equal to the number of protons The outermost shell of electrons is called the VALENCE SHELL which holds the VALENCE ELECTRONS.

Take out Bohr Diagram Sheet.

Electrons (e-):



Change ENERGY LEVELS when the atom GAINS or LOSES energy The most stable electron arrangement

Electrons (e-):



Current Theory –

 

“Electron Cloud Model” (p116-17) Shows POSSIBLE locations of electrons around nucleus It’s a good approximation of how electrons behave

Electrons (e-):



ORBITALS: the most likely location of the electrons in the cloud.

Electrons (e-):



Atoms of the same element with different number of ELECTRONS are called IONS

IONS: form to make the outermost shell stable