Chapter 2: Atoms, Molecules, and Ions Study Guide

John Dalton's Atomic Theory (5 postulate)

1. Matter is made up of atoms (right)

2. Elements consist of one type of atom (right)

   -Mass is the same for all atoms of that element (wrong)

   -Atoms of the same element have identical chemical properties (not completely right or wrong)

3. Atoms of 1 element aren't the same as other elements (right)

4. A compound = 2+ atoms of 2+ elements in small, whole number ratios (right)

5. Atoms aren't created/destroyed in a chemical change but are rearranged (right)

Did John Dalton believe that the atom is indivisible?

Yes

are atoms indivisible?

No

Law of Definite Proportions (from Dalton)

compounds contain the same elements in the same proportion by mass

JJ Thomson's experiment

Cathode ray experiment

What did the cathode ray tube experiment discover?

allowed us to calculate the charge-to-mass ratio of cathode ray particle, aka electrons (negatively charged w/a mass of 1/1000 of an atom

Robert Millikan's experiment

"oil drop"

What did the oil drop experiment prove?

allowed us to determine the charge and mass of an electron (9.107 x 10^-31 kg)

JJ Thomason's experiment

plum pudding model

What did the plum pudding model discover?

protons and electrons

Ernest Rutherford experiment

Gold foil experiment

How did the gold foil experiment work?

positive alpha particles were shot at thin gold foil, most passed directly through and very few were deflected back

What did the gold foil experiment discover?

1. since the alpha particles were getting deflected, they must have hit a positive charge (that being the nucleus)

2. An atom is mostly empty space

James Chadwick discovered what?

discovered the neutron

Neutron (n^0)

uncharged subatomic particle w/mass = to a proton

Proton (p^+)

positively charged subatomic particle found in the nucleus

Electron (e^-)

A subatomic particle that has a negative charge

How heavy are neutrons, electrons, and protons?

1. Neutrons: ~1 amu; 1.0087 amu

2. Electrons: 0.00055 amu

3. Protons: ~1 amu; 1.0073 amu

Isotope

atoms of the same element that differ in mass; same number of protons, different number of neutrons

T or f: the nucleus is 1,000 times smaller than the diameter of an atom

t

Electron cloud

where electrons are located

Atomic Mass Unit (amu)

1/12 the mass of a carbon-12 atom; used as the mass unit for an atom

1 amu

1.6605 x 10^-24g

Fundamental Charge (e)

the charge of an electron

Fundamental charge (e) =

1.602 x 10^-14C

Atomic Number (Z)

the number of protons

Mass Number (A)

sum of protons and neutrons; not on the periodic table

Neutral Atom

proton = electron

Ion

atom with a charge, proton isn't = electron

Atomic Charge

difference of protons - electrons

Atoms and Molecules

1. Take in electrons = more negative

2. Lose electrons = more positive

Anion

gains electron

Cation

lose electron

Chemical Symbol

abbreviation for an element

Isotope Notation

don't always have all of the numbers (mass number, atomic number, and charge)

What are the 3 isotopes of Hydrogen?

1. Protium

2. Deuterium

3. Tritium

Average Atomic Mass

average of isotopes of an elements mass

epsilon

summation

Average Atomic Mass formula

(Percent to decimal)(mass) + (percent to decimal)(mass)