H Chem Unit 2

Mole

Mole

SI unit for amount of substance, abbreviated as mol

Avogadro’s Number

6.02 × 10²³ atoms ( = 1 mole)

conversion factor for mole and actual amount of particles

Molar mass (per mass)

The mass of one mole of a kind of chemical. Serves as conversion factor between mass (g) and mole

Atomic Mass

Molar mass of each element atom

Found in the periodic table + unit is g/mole

(Chemical) Symbol

All elements in the Periodic Table have symbols that are recognized worldwide.

A chemical symbol is an abbreviation of a name of an element.

Represented by a single capital letter or by a capital letter followed by a lowercase letter.

Identifies types of elements in a molecule

Chemical Formula

Combination of symbols that represent a particular molecule

Indicates which elements are present in the compound + in what proportions

Ratio Examples

• H₂O

  • 2 : 1 (hydrogen to oxygen)

• Fe₂O₃

  • 2:3. (iron to oxygen)

Subscripts

Whole numbers on lower right hand side of each element symbol in the formula of a molecule. Tells you the number of atoms of each element in the molecule.

No subscript = Quantity of 1

Lower right hand side of parentheses that surround some groups of atoms→ indicate amount of the atom groups

Conversion Diagram

Democritus (2)

1st to propose that matter is made of tiny solid particles.

He called particles atomos, meaning uncuttable

Law of Conservation of Mass

“Discovered” in 1789:

mass of ALL reactants = mass of ALL products

Law of Definite Proportions

(Fixed ratio) Any amount of a compound is composed of elements in the same proportions by mass.

Law of Multiple Proportions

When two elements form more than one compound, the ratios of the masses of the second element that combine w/ one gram of the first can be reduced to small whole numbers

John Dalton’s Atomic Theory + Revision (1)

Him: All matter is made of atoms which are indivisible and could not be created or destroyed → explains Law of Conservation of Mass + Law of Definite Proportions

Revision:

• Atoms are divisible into smaller particles called subatomic particles (protons, neutrons, + electrons) that can be removed

• Atoms are not created, destroyed, or changed into any other elements in chemical reactions

John Dalton’s Atomic Theory + Revision (2)

Him: Atoms of the same element are identical and have the same size, mass, and physical and chemical properties.

Revision:

• Atoms of the same element are identical and have the same size and physical + chemical properties

• Atoms of the same element can have different masses, which are called isotopes

John Dalton’s Atomic Theory + Revision (3)

The properties of the atoms of one element are different from those of another element

John Dalton’s Atomic Theory + Revision (4)

Atoms of different elements combine in whole number ratios to make compounds → explains Law of Definite Proportions and Multiple Proportions

Dalton’s Model Name

“Billiard Ball Model”

Thomson was the 1st to discover a subatomic particle — the ___1___, which is ____2____ charged

1 → electron

2 → negative

Thomson’s experiments used _____ rays

cathode

Thomson’s atomic model is known as the _____ ______ model.

plum pudding

Alpha particles are a type of ______ charged radiation

positive

When shot at a piece of gold foil, most alpha particles ____________1_______________ like the foil was not there. But occasionally, some alpha particles _________2________ as if it has hit something.

1 → passed straight through the foil like the foil was not there

2 → went straight back or were deflected,

The Gold Foil experiment led to the discovery of the ______, which is the center of the atom.

nucleus

The core of an atom is ___1______ charged, called __2____.

1 → small positively

2 → nucleus

Bohr proposed that electrons are found in circular ____1_____ around the ____2___ in different distances.

1 → fixed orbits / shells

2 → nucleus