Atomic Structure Chemistry: Chapter 4

AtomsBuilding block of matter Cannot be seen Known to exist through indirect evidence. Gathering information w/o actually seeing or touching the object. Used to develop a mental picture or model. Ex. gravity

History of the atom overview 

Greek Model 2400 years ago, Greek philosopher Democritus 1st to use the term “atom” meaning “indivisible” or “not to be cut” Ancient Greeks believed matter was made of 4 basic elements: fire, air, water, and earth

Dalton’s Model Early 1800’s, English chemist, John Dalton Meteorologist Developed the atomic theory 1.All elements are composed of atoms. 2.Atoms of the same element are identical. 3.Atoms of different elements are different. 4.Compounds are formed by joining 2 or more atoms.

1897 Proved atoms were made up of even smaller particles Discovered corpuscles electrons Model called “plum pudding” Thomson’s Model

Rutherford’s Model 1908 Discovered that atoms have dense, positively charged nucleus Fired charged particles at gold foil, some went through while others were deflected.

Subatomic particles Protons  Positively charged; +1 Neutrons  No charge  In the nucleus Electrons  Negative charge; -1  Outside the nucleus Distinguishing Characteristics: Mass Charge Location

Atomic Number Number of p+ in the nucleus Each element has a certain number of p+ Mass Number or Atomic mass Sum of p+ and neutrons Mass # = atomic # + neutrons Li Chemical symbol 3 7 Atomic # Mass # Also equal to the number of e-

Isotopes Atoms of the same element Have different number of neutrons, but the same number of protons & electrons They have the same atomic #,but different mass # because of the # of neutrons Ex. (O-16, O-17, and O-18) Each O has 8 protons, but the neutrons vary

Bohr’s Model 1913 Discovered that electrons move in energy levels (orbits) around the nucleus Called the “solar system model”

Summary of history of the atom  artel/Chemistry/Ch3/History%20of%20At om%20Notes.pdf artel/Chemistry/Ch3/History%20of%20At om%20Notes.pdf artel/Chemistry/Ch3/History%20of%20At om%20Notes.pdf

 science.co.uk/atomicstructure1.htm science.co.uk/atomicstructure1.htm science.co.uk/atomicstructure1.htm

Arrangement of electrons Electrons are in energy levels within an electron cloud. 1 st energy level can hold 2 e- Around the nucleus 2 nd energy level can hold 8 e- 3 rd energy level can hold 8 e-  Each orbital can contain 2 electrons 4 th energy level can hold 18 e-

Electron Configuration Arrangement of electrons in orbitals Most stable in the lowest possible energy level If all electrons have the lowest possible energies, the atom is in ground state

Ex. Magnesium Symbol  Mg Atomic Number  12# of p+  12 # of e-  12 1 st energy level  ____ (can hold 2) 2 nd energy level  ____ (can hold 8) 3 rd energy level  ____ (can hold 8) 2 8 2

12 p+ Magnesium

Ex. Aluminum Symbol  Al Atomic Number  13# of p+  13 # of e-  13 1 st energy level  ____ (can hold 2) 2 nd energy level  ____ (can hold 8) 3 rd energy level  ____ (can hold 8) 2 8 3

13 p+ Aluminum

Ex. Fluorine Symbol  F Atomic Number  9# of p+  9 # of e-  9 1 st energy level  ____ (can hold 2) 2 nd energy level  ____ (can hold 8) 3 rd energy level  ____ (can hold 8) 2 7 none

9 p+ Fluorine

Practice Determine the # of e- in the following elements. Draw their electron configuration. Lithium Oxygen Helium Titanium Beryllium Nickel Sulfur Argon Carbon Zinc

Preparing for tomorrow  Tomorrow you will be having a lab where you concentrate on Atomic Structure  Make a list of supplies that you will need in order to make a model of any atom of your choosing beyond element #10 Oxygen  Bring your supplies to class or drop them by room 604 tomorrow morning

Lab Lab  This lab you will be creating a Bohr Model of any atom that you choose beyond Oxygen  You must bring your own supplies for this  EX: cookies with icing to hold the P + N 0 and E - in place  Make a key that show the atomic name, number, symbol and atomic mass number

After you complete your model…  Once you have completed your model you are to have your teacher check you off. You will need to have your key and be able to answer questions about your model ie.. How did you determine the number of protons, neutrons electrons etc.