Chem Week 2- Atomic Structure, The Mole, and Molecular Formula

John Dalton Rule #1

Atoms are exceedingly small particles that make up matter.

John Dalton Rule #2

Atoms in an element are identical with a mass that charaterizes the element

John Dalton Rule #3

Atoms of one element differ in properties from atoms of all other elements

John Dalton Rule #4

A compound consists of atoms of two or more elements combined in a small, whole-number ratio

John Dalton Rule #5

Atoms are neither created nor destroyed during a chemical reaction but instead are rearranged.

Micheal Faraday

Determined atoms were connected to electricity.

Solid Sphere Model

John Dalton

1803

JJ Thompson

Discovered Electrons through electricity

• Sent electrical currents through a glass tube

• Plum Pudding Model - some negative charges surrounded by positive

• 1904

Ernest Rutherford

New Zealand Scientist who performed the Gold Foil experiment and discovered PROTONS.

• Nuclear Model

• 1911

Rutherford “rules”

• There must be empty space inside of an atom

• Since Alpha particles are positive and deflecting they must be repelled by positive parts of the atom

• Since only so few particles were deflected at all, there must be a very small cluster of positive charge in the center of the atom

Atomic Number

The number of protons an element has

Three subatomic particles and their charges

1. Protons (positive or +)

2. Neutrons (neutral)

3. Electrons (negative or -)

Mass Number

The mass of an element, the number of neutrons plus protons (whole numbers)

Electrons are negligible for mass

Atom

Element that is neutrally charged

number of protons equal number of electrons

Ions

Have a charge, meaning that the number of protons is not equal to the number of electrons.

Cation

Positive charge; more protons than electrons

Anions

Negative Charge ; more electrons than protons

Isotopes

Atom of an element that has the same number of protons, but a different number of neutrons

Atomic Mass

The average masses of all isotopes of each element (not a whole number)

Diatomic Molecules

Pure elements where two atoms are bonded together; usually gases

Examples: I_2, Br₂, F₂,O₂, N₂,H₂,Cl₂

Mole

A chemical quantity that converts between the mass of a substance and the number of atoms/molecules/ions in the substance

Avogadro’s Number

6.02 X 10²³ units/mole

Units can be molecules/atoms/ions

Molar Mass

The mass in grams of 1 mole of that substance (g/mol)

Number of Atoms

should be a huge number

Number of moles

Should be a small number

Why are electrons negligible?

Electrons are too small.

Sodium (Na) has an atomic number of 11. How many neutrons does it contain if its mass number is 23?

23-11=12

12 neutrons

Why is the atomic mass not a whole number?

They are naturally mixtures of isotopes

Colloids

Microscopic nanoparticles that are suspended in another medium or solution.

kilo

10³

centi

10^-2

Milli

10^-3

Micro

10^-6

nano

10^-9

Density of Water

1 g/mL