Atomic structure study guide

What did John Dalton develop?

He developed and published a theory on how atoms look and behave in 1808.

What was Dalton's 1st Postulate?

All elements are composed of tiny INDIVISBLE particles called atoms

What was the correction to his 1st postulate?

Atoms are DIVISBLE, they are compromised with protons, neutrons, and electrons.

What was Dalton's 2nd postulate?

Atoms of the same element are IDENTICAL

What was the correction to his 2nd postulate?

It is no longer accepted due to the discovery of isotopes

What was Dalton's 3rd postulate?

Atoms of different elements can chemically combine with one another in simple whole number ratios to form COMPOUNDS

What was Dalton's 4th postulate?

CHEMICAL REACTIONS occur when atoms are separated, joined, or arranged. Atoms of one element are NEVER changed into atoms of another element as a result of a chemical reaction.

Who discovered the electron by the Cathode Ray Experiment?

J.J Thomson

What were the observations of the Cathode Ray Experiment?

1. Ray bends in magnetic field

2. Ray bends toward positive plate in electric field

3. Ray is identical for any cathode

What were the conclusions of the Cathode Ray Experiment?

1. Consists of charged particles

2. Consists of negative particles

3. Particles are found in all matter

What was J.J Thomson's model?

Thomson's Plum Pudding Model

Describe the Model.

-Atoms are big spheres of positive charge with electrons spread in it

• like a 3D chocolate chip cookie/plum pie

What did Ernest Rutherford prove in 1911?

-An atom I mostly empty space

-all positive charges were located in a small central area called the nucleus

What was the experiment that Rutherford used?

Gold Foil experiment

What did the Gold Foil experiment consist of?

• alpha particles are helium Nuclei

-particles fired at a thin sheet of gold foil

-particle hits on the detecting screen (film) are recorded

What were the results of the Gold foil experiment?

• most particles passed straight through

• some were partiality deflected

• very few deflected fully

What were Rutherford's conclusions?

• the nucleus is dense, positively charged

-negative electrons move around the nucleus

What did Eugene Goldstein discover in 1886?

protons

(particles flowing in opposite direction of cathode rays. Called them Canal rays and discovered they were positively charged)

What did James Chadwick discover in 1932?

Neutrons

What is the number on the top left of the element symbol?

Atomic Mass

What is the number on the bottom left of the element symbol?

Atomic Number

Atoms with the same number of protons but different numbers of neutrons.

Isotope

How do you name an isotope?

Put the atomic mass after the name of the element

What is the equation for average atomic mass?

Average mass = (Mass # x %) + (Mass # x %)…

What is the Octet Rule?

-atoms want 8 electrons like noble gases

• nobles have completely filled energy levels that are stable

-Atoms that don't have to lose, gain, or share to reach this

What is Lewis Dot structures?

-first 2 valence electrons pair together

-3rd, 4th, 5th don't pair with other electrons