Chemistry Ch. 2 - Atoms, Molecules, and Ions

Atomic Force Microscopy

A way to see atoms using a sharp tip with lasers

Scanning Tunneling Microscopy

Another way to see atoms using an electron beam

Dalton’s Atomic Theory and the 4 Postulates

1) Everything is made of Atoms
2) All atoms of 1 element are identical, but different elements have different atoms
3) One elemental atom (like oxygen) cannot be changed into a differnt elemental atom (like nitrogen)
4) Several elemental atoms can come together to make compounds and a specific compound will always be made in the same composition

Law of Constant Composition

Based on postulate 4. The composition of a compound will never change; it will always have the same percentages of elements
Ex) any water molecule will always have one oxygen and two hydrogens

Law of Conservation of Mass

Based on postulate 3. Mass is never lost or gained, total mass does not change in chemical reactions.

Law of Multiple Proportions

Based on all postulates. The same elements can form more than one compound
Ex) With just hydrogen and oxygen, you can make water (H2O) or hydrogen peroxide (H2O2)

Who discovered Protons?

Ernest Rutherford

Who discovered Electrons?

J.J. Thompson

Who discovered Neutrons?

James Chadwick

What makes up the volume of electrons

The electron cloud

What is the electron mass

9.1 × 10^-28

What do protons do and their relative charge?

Determine the identity of the atoms, +1 amu

What do neutrons do?

They glue/keep the atom together

What do electrons do and their relative charge?

They determine the reactivity, -1 amu

How to find the mass number?

Protons + Neutrons

Where is mass number, atomic number, and charge located on an elements periodic table

Mass number is on top, atomic number on bottom, and charge on the top right.

Isotope

Different versions of the same element due to different number of neutrons.

Groups

Vertical columns with the same physical and chemical properties

Periods

Horizontal rows

Where are the main groups and transition metals on the periodic table

The main group includes the two tall columns on each side and the transition metals in the middle and bottom

Properties of Metals

Shiny, conductive, lustrous, malleable, solids at room temperature, high melting point, high malleability, lose electrons easily (low ionization energy, low electronegativities)

Properties of Nonmetals

Most are gases at room temperature, hard and brittle, low/no luster, low melting points, gains electrons easily (high ionization energies, high electronegativities), good insulators (because theyre poor conductors)

Metalloids

They are good semiconductors

Molecular Compounds

Almost always nonmetals

Covalent Bonding

C.C. = Caring Covalent, covalent bonding shares electrons

Molecular Formulas

The exact number of atoms in each element
Ex) C₆H₁₂O₆

Empirical Formula

The lowest whole number ratio of atoms in each element
Ex) CH₂O

Polyatomic Ions

Compounds with a net charge
Ex) SO₃^-2 is Sulfite