Warm Up

1. What evidence did Bohr use for his model?

2. What evidence did Schrodinger use for his model?

Take 1

Next Playa!Bohr

• Experiment: Hydrogen Emission Spectrum– Hydrogen emits only specific wavelengths of

light when it gives off energy

• Result:– Light is a wave and a particle– Light has different energies– When atoms lose energy they lose it in

definite amounts (aka quanta)

Hydrogen Emission Spectrum

Bohr Models of Atoms (1913)

• Depict an atom as a small, positively charged nucleus surrounded by electrons that travel in circular energy levels (aka orbitals) around nucleus

16 p+

16 no

Sulfur: 16 protons

16 neutrons

16 electrons

Bohr: Energy Levels

• Energy levels: paths around the nucleus that electrons travel

• Electrons can ONLY exist in those energy levels, NEVER between

• Energy levels are also known as orbitals• When you add energy to an atom the electrons

jump to a higher energy level (excited state)– When that electron loses energy and falls back down

to its original orbital (ground state) you get light (energy released)

New Notes!

Chemical ReactionsSituation where atoms

rearrange to make new substances.

Reactants

BEFORE

•What you start with.

•What reacts or rearranges

Reactants Products

BEFORE

•What you start with.

•What reacts or rearranges

AFTER

•What you end with.

•What is produced.

How do you know a reaction happened?

Evidence Example

temperature change

color change

precipitate forms

gas released

smell

What can happen in a chemical reaction?

• Old bonds between atoms are broken

• New bonds between atoms are formed

• Matter is CONSERVED!

Review- Types of Reactions

• Synthesis: A + B -> AB

• Decomposition: AB -> A + B

• Single Replacement: AB + C -> AC + B

• Double Replacement:AB + CD -> AD + CB

Double Replacement

• How to predict products?– Just switch partners– Cations (positive ions) still come first in the

formula– Anions (negative ions) still come last in the

formula– Polyatomic ions move as a unit– Example?

Practice Double Replacement (aka partner switch!)

What forms from:

1. Calcium sulfide and magnesium oxide

2. Potassium chloride and hydrogen carbonate

3. Sodium hydroxide and lithium bromide

Practice Double Replacement (aka partner switch!)

What forms from:

1. NaCl and LiF

2. CaO and MgS

3. MgCl2 and CaI2

4. CaF2 and Li2O

How to find the charge?

• Charges of polyatomic ions are on the back of your periodic table

• Elements in columns 1A-8A follow a pattern:

Column 1A 2A 3A 4A 5A 6A 7A 8A

Charge +1 +2 +3 -/+4 -3 -2 -1 No ion

Why those charges?

• Review electron loss/gain

Practice by writing the charge of each element or polyatomic ion

• CO3

• OH• SO4

• B• C• N• Na• Be• F• S

Practice by writing the correct subscripts for the formulas

• MgF

• CaO

• NaN

• BCl

• LiS

• MgN

• AlO

Remastery quiz

• Work silently and alone for full credit

Sum Up

• Top ten: how’d we do?

• What did we learn today?