LECTURE                    THE STRUCTURE OF ATOMS

In this lecture you will learn:

The structure of atoms: the nucleus

 
 

PROTONS

- elements are defined by how many protons they have
- have a positive + change
-- since protons (+) repel each other, "nuclear" forces hold the nucleus together.
- have MASS
- the more protons and neutrons, the heavier the element
 
 
 
 
 
 

NEUTRONS

- have no charge
- have MASS
- help hold protons together
- more or less neutrons doesnt change element status but affects radioactivity


 
The structure of atoms: the electrons
ELECTRONS 

-- the electrons "orbit" the nucleus
-- In an atom, the location of electrons in orbit cannot be precisely determined. Instead, the location of electrons are given as an estimate or probability of where they will be at any time.
- this estimate of where electrons are is called a "SHELL". electrons are assigned shell orbits from the inside near the nucleus outward.
- they have mass, altho a lot less than protons and neutrons
- in hydrogen, there is just one electron, in helium, two
 


SHELLS are where the electrons hang out
- shells represent discrete energy levels
- no two electrons are in the same place at the same time
- chemical reactivity is dictated by how many electrons there are in the outer shell
- electrons fill the shells from the inside near the nucleus outward
- shells exist even when there isnt an electron in it
- Between the electrons is emptiness. A lot of emptiness.

-- lets say that your foot (12 inches) is the nucleus, then the atoms are moving in an area of about 20 miles, up to Port Washington, out past Waukesha and down around Racine. That is a lot of space.
- this means that the electron orbits are about 100,000 times larger than the nucleus.

 
electromagnetic force = The attraction of the positive (+) charge of protons and the negative (-) charge of electrons which holds the atom together 
ALL PROTONS are interchangeable with other protons 

ALL NEUTRONS are interchangeable with other neutrons

ALL ELECTRONS are interchangeable with other electrons

- What is unique about each atom of a given element is HOW MANY PROTONS THERE ARE

- IF they have more or less neutrons than usual, they become UNSTABLE and radioactive

- IF they have more or less electrons than usual, they become IONS and are "charged".  If positively charged they are called "cations" (cats are positive)  and if negatively charged they are called "anions" (onions are negative for sweet breath - little memory trick). 

- elements generally have the same number of neutrons and electrons as there are protons, however, the number of neutrons may vary and elements may lose or gain a few electrons but will still be the same element

- if they lose one or more proton, in radioactive decay for example, then they become a TOTALLY DIFFERENT ELEMENT

BUT WHAT EXACTLY MAKES DIFFERENT ELEMENTS DIFFERENT????
HOW MANY PROTONS DETERMINES WHAT THE ELEMENT IS!!!!!

ATOMS ARE UNIQUE AND INDIVISIBLE
- even tho constituent parts of every atom are interchangeable.



REVIEW QUESTIONS:

Draw an atom of hydrogen showing all the parts and give their characteristics

fill in the table

  
proton neutron electron
where is it found      
charge      
mass      
other characteristics      
Discuss where electrons are found.
What are shells?
What particle determines what element an atom is?
What happens if an element has more or less protons than usual?
What happens if an element has more or less neutrons than usual?
What happens if an element has more or less electrons than usual?
What is a cation?
What is an anion?
Why are atoms unique?
What is the current theory of atomic structure?
What are the characteristics of protons?
What are the characteristics of neutrons?
What are the characteristics of electrons?