Science Unit 3: Chemistry

Elements:

• AKA Atoms

• The “smallest” unit of matter that ALL KNOWN objects are made up of

Mole number (Avagadros number)

• How many atoms in a small pile of carbon

• 6.02 × 10^ 23

What are atoms mostly made up of?

• MOSTLY empty space

• Subatomic particles

Electrons

• Symbol: -

• Negative charge

• Located in orbitals

• Mass: 1/836 AMU

Protons

• Symbol: +

• Positive charge

• Located in nucleus

• Mass: 1835/1836 AMU

Neutrons

• Symbol: (nada)

• Neutral

• Located in center

• Mass: 1 AMU

How do we determine the # of neutrons?

Atomic weight - atomic number

ATOMIC # =…

NUMBER of PROTONS

(Round that number)

number of electrons=…

Atomic number OR Protons+ Neutron

Electron Orbitals

• Location where electrons can be found

• First 3 orbitals: KLM

• You cannot put electrons in the next orbital unless you fill the previous orbital

Bohr Model

Model of an element that shows the number of electrons in each orbit of an element

Valence Electrons

Electrons that are located on the outermost orbital

Lewis Dot Structure

Shows only the valence electrons

Families

• Pattern on the periodic table

• Same number of valence electrons

Periods

• Pattern on the periodic table

• Have the same number of orbitals

Compounds

2 or more elements combined

Subscript

Tells us how many elements are in that compound

What do all elements want?

FULL VALENCE

Do metals gain or lose electrons to reach full valence

Lose

Do nonmetals gain or lose electrons to get full valence

Lose

Oxidation state

• The charge of an element after it bonds

• Can help us determine what the element can bond to

Metal’s oxidation state

POSITIVE

Nonmetals oxidation state

NEGATIVE

Ionic Compounds

• Metal + Non metal

• Metal gives its valence electrons to the nonmetal who takes it in

• SOLIDS

• Bond strength: Strong

Covalent Compounds

• The valence electrons are shared between the nonmetals

• Nonmetals + nonmetal

• Gasses or liquids

• Weak bond strength

How to draw an ionic bond

1. Draw the lewis dot structure

2. Draw an arrow from the metal’s valence electrons to the nonmetal valence electrons to show the transfer of valence electrons reaching FULL VALENCE

How to draw covalent bonds

1. Draw the Lewis Dot structure

2. Move the dots around so the electrons are easy to SHARE

3. Circle full valence for each atom

4. The overlap of the circles tells us the shared electrons!

Synthesis Reaction

When 2 or more simple things combine to make 1 more complex thing

Decomposition Reaction

When 1 complex thing “Breaks down” into 2 or more simple things

Single-replacement Reaction

An element combines w/ a compound to create a new compound and new element

Double replacement reaction

2 compounds react to form 2 completely different compounds

Combustion reaction

Carbon+Hydrogen+Oxygen = Carbon + Oxygen + Hydrogen + energy

Heterogenous Mixtures

A physical combination where you can see the individual substances

Homogenous Mixtures

A physical combination where you can’t see the individual substances

How can you separate mixtures?

Physically, not chemically

Filtration

Separates solids from liquids

Melting Point

Separates solids from solids (brass and copper)

Magnetism

Separates magnetic materials from non-magnetic ones

Distillation

Separates substances based on boiling points

Boiling/ Evaporation

Removes a liquid to leave a solid behind

Sieving

Separates solids of different sizes

What is solubility

The ability of a solute to dissolve in a solvent to form a solution

Solute

The substance being dissolved

Solvent

The substance that dissolves the solute

Solution

A uniform mixture of solute and solvent

Saturation

When a solution cannot dissolve any more solute at a given temperature

Soluble

A substance that dissolves well in a substance

Insoluble

A substance does not dissolve well (sand in water)

Precipitate

The process where a solid forms from a solution and either sinks to the bottom or remains suspended

Factors affecting solubility: Temperature

• Higher the temperature the greater the solubility for solids

• Higher the temperature the lower the solubility for gases

Factors affecting solubility: Pressure

• The higher the pressure the greater the solubility for gases

• No affect on solubility of a solid

Unsaturated

A solution s able to dissolve more solute

Saturated

A solution is at its maximum amount of dissolved solute

Supersaturated (NoT)

Contains more solute than normally possible at a given temperature

Solubility Curve

A graph showing how solubility changes with temperature