Bell Ringer Sept. 15 Which element is most like Fluorine? Explain why?

HISTORY OF THE ATOM 460 BC Democritus develops the idea of atoms he pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMA (greek for indivisible)

HISTORY OF THE ATOM 1808 John Dalton suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them ATOMS

HISTORY OF THE ATOM 1898 Joseph John Thompson found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRON

HISTORY OF THE ATOM Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge 1904 like plums surrounded by pudding. PLUM PUDDING MODEL

HISTORY OF THE ATOM 1910 Ernest Rutherford Conducted famous experiment called the “Gold Foil Experiment” He fired Helium nuclei at a piece of gold foil which was only a few atoms thick. He found that almost of them passed through (About 1 in 10,000 hit).

HISTORY OF THE ATOM gold foil helium nuclei They found that while most of the helium nuclei passed through the foil, a small number were deflected and, to their surprise, some helium nuclei bounced straight back. helium nuclei

HISTORY OF THE ATOM Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus. He suggested that the positive charge( PROTON) was all in a central nucleus. With this holding the electrons in place by electrical attraction However, this was not the end of the story.

HISTORY OF THE ATOM 1913 Niels Bohr Bohr refined Rutherford's idea by adding that the electrons were in orbitals. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.

Bohr’s Atom electrons in orbits nucleus

Dalton’s Atomic Theory Theory that atoms are the fundamental building blocks of matter.

1. Each element is composed of extremely small particles called atoms.

2. All atoms of a given element are identical to one another in mass and other properties ;  but the atoms of one element are different from the atoms of all other elements. Nitrogen AtomOxygen Atom

3. Atoms of an element are NOT changed into atoms of a different element by chemical reactions.  atoms are neither created nor destroyed in chemical reactions.

4. Compounds are formed when atoms of more than one element combine  a given compound always has the same relative number and kind of atoms. H H O

S.MORRIS 2006

Cornell Notes

HELIUM ATOM + N N proton electron neutron Shell What do these particles consist of?

Properties of Subatomic Particles ParticleSymbolLocationCharge Electrone-e- Around nucleus 1– Protonp+Nucleus1+ Neutronn0n0 nucleus0

Atomic Structure and the Periodic Table 14 Si Silicon Atomic number = number of protons Symbol Name Atomic Mass Number of protons = number of electrons Number of neutrons = Atomic Mass (rounded) - number of protons (relative mass)

Practice Complete the following chart: NameSymbol Relative mass # protons # neutrons # electrons Lithium Mg 26 16

Closing TaskSept. 15 NameSymbol Relative mass # protons # neutrons # electrons Nitrogen Be

What do we know? Atoms have 2 main parts Electron cloud -- contains electrons Nucleus – contains protons and neutrons Electrons = e- Protons = p+ Neutrons = n 0

What do you need to know? There are 7 possible orbitals You can determine how many orbitals your model has by looking at what period (row) the element is on The orbitals hold a specific number of electrons (which is the same as the atomic number)

How many electrons per orbital? Period 1  orbital (ring) 1: 2 e- Period 2  orbital (ring) 1: 2 e- orbital (ring) 2: 8 e- Period 3  orbital (ring) 1: 2 e- orbital (ring) 2: 8 e- orbital (ring) 3: 8 e- Period 4  orbital (ring) 1: 2 e- orbital (ring) 2: 8 e- orbital (ring) 3: 18 e- orbital (ring) 4: 8 e- *EXCEPTIONS: Potassium and Calcium (2, 8, 8, 8)

Information to create a Bohr model Element symbol Atomic number Atomic mass Protons Electrons Neutrons

Examples: Lets try Magnesium: How many protons? How many neutrons? How many electrons? How many orbitals?

Bohr model for Mg 12p+ 12n

Example 2 Let try Fluorine: How many protons? How many neutrons? How many electrons? How many orbitals?

Lewis Dot Structures Valence electrons are the electrons found in the outermost orbital of the atom. Structure that uses dots around the element’s symbol to represent the valence electrons in the atom Rule Do NOT pair up electrons (dots) until you have 1 electron on all four sides of the symbol. (Electrons try to be as far apart from each other as they can)

Now your turn………..

To turn in: Draw the following Bohr Models: 1. Sodium 2. Hydrogen 3. Carbon 4. Silicon 5. Oxygen 6. Chlorine 7. Argon 8. Calcium 9. Sulfur 10. Neon Draw the following Lewis Dot Diagrams: 1. Chlorine 2. Arsenic 3. Krypton 4. Gallium 5. Germanium 6. Lead 7. Xeon 8. Barium 9. Phosphorus 10. Silicon