Electrons in Atoms

Bohr’s Model  Electrons move like planets around the sun.  In circular orbits at different levels.  Amounts of energy separate one level from another.

The Bohr Model of the Atom The Bohr Model of the Atom A.Electrons of hydrogen circle the nucleus in orbits 1. orbits have a fixed amount of energy 1. orbits have a fixed amount of energy in the ground state in the ground state 2. orbits are a fixed distance from the 2. orbits are a fixed distance from the nucleus nucleus 3. orbits furthest from the nucleus have 3. orbits furthest from the nucleus have the greatest energy the greatest energy

4. Electrons in the ground state can absorb quanta of energy – become excited- and move to a higher orbit 5. Electrons emit quanta of energy when they return to the ground state they return to the ground state 6. Model applies only to hydrogen atoms

Niels Bohr (1885 – 1962) Bohr Model of the Atom

Bohr’s Model Nucleus Electron Orbit Energy Levels

Bohr’s Model Increasing energy Nucleus First Second Third Fourth Fifth }  Further away from the nucleus means more energy.  There is no “in between” energy  Energy Levels

Bohr  Make a model of Bohr’s Hydrogen. Bohr was only correct about Hydrogen.  Draw a nucleus  Then draw the electron.

Changing the energy  Let’s look at a hydrogen atom

Changing the energy  Heat or electricity or light can move the electron up energy levels

Changing the energy  As the electron falls back to ground state it gives the energy back as light

 May fall down in steps  Each with a different energy Changing the energy

II.Heisenberg Uncertainty Principle IIIIt is impossible to know exactly the position and velocity of a particle at the same time. TTTThe better we know one, the less we know the other. TTTThe act of measuring changes the properties. LLLLook at the fan

Covalent clip

I.The Covalent Bond A. Why do atoms form bonds? 1. To get 8 valence shell electrons 1. To get 8 valence shell electrons (noble gas configuration) (noble gas configuration) 2. more stable configuration - 2. more stable configuration - less potential energy less potential energy B. Definition of Covalent Bond 1. bond resulting from sharing electrons 1. bond resulting from sharing electrons 2. share electrons by overlapping of 2. share electrons by overlapping of orbitals orbitals

I.The Covalent Bond A. Why do atoms form bonds? 1. To get 8 valence shell electrons 1. To get 8 valence shell electrons (noble gas configuration) (noble gas configuration) 2. more stable configuration - 2. more stable configuration - less potential energy less potential energy B. Definition of Covalent Bond 1. bond resulting from sharing electrons 1. bond resulting from sharing electrons 2. share electrons by overlapping of 2. share electrons by overlapping of orbitals orbitals

Covalent Bonds – Sharing of Electrons

The Lewis dot structure for Oxygen O Oxygen is in group VIA so it has 6 valence electrons

The Lewis dot structure for Chlorine Cl chlorine is in group VIIA so it has 7 valence electrons

The Lewis dot structure for calcium Ca calcium is in group IIA so it has 2 valence electrons

Making calcium chloride +Ca Cl Ca( Cl ) 2

Lewis dot structure of a compound NH3NH3 N H H H

NH 3 1)How many valence electrons does N have? N is in group VA so it has 5 valence electrons 2) How many valence electrons does H have? H is in group IA so each H has one valence electron 3) How many valence electrons does Neon have.

Water - H 2 O H O Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

Water  Put the pieces together  The first hydrogen is happy  The oxygen still wants one more H O

Water  The second hydrogen attaches  Every atom has full energy levels H O H

Lewis structure  1. PH 3  2. H 2 S  3. HCl  4. CCl 4  5. SiH 4

Lesson 3 Lewis structure  Use molecular model kit to build  1. PH 3 2. H 2 S  3. HCl4. CCl 4  5. SiH 4 6. CH 4   7. ClF 3 8. PCl 5   9. SO N 2 O 5

1. 1.ClF PCl SO N 2 O 5

Isomers- Build the molecule On the right using springs for double bonds.

3. diatomic molecules (contain two atoms) a. periodic table (1,1-7--->group 17) a. periodic table (1,1-7--->group 17) elements that form diatomic molecules elements that form diatomic molecules H 2 N 2 O 2 F 2 Cl 2 Br 2 H 2 N 2 O 2 F 2 Cl 2 Br 2 b. compounds can also be diatomic b. compounds can also be diatomic HCl CO NO HF HI HBr HCl CO NO HF HI HBr

C. Examples and Diagrams H 2 F 2 HF H 2 F 2 HF Make a drawing D. What is a molecule? Make a drawing D. What is a molecule? 1. two or more atoms bonded covalently 1. two or more atoms bonded covalently 2. examples- Make a drawing 2. examples- Make a drawing (usually two or more nonmetals) (usually two or more nonmetals) H 2 O NH 3 CH 4 N 2 O 5 HCl C 6 H 12 O 6 H 2 O NH 3 CH 4 N 2 O 5 HCl C 6 H 12 O 6