The Structure of the Atom

Laws & Theories

100

Mass is neither created nor destroyed during ordinary chemical reactions or physical changes.

What is the Law of Conservation of Mass?

200

A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound

What is the Law of Definite Proportions?

300

Identify the following theory:

• All matter is composed of extremely small particles called atoms.
• Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
• Atoms cannot be subdivided, created, or destroyed.
• Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
• In chemical reactions, atoms are combined, separated, and arranged.

What is the Dalton's Atomic Theory?

400

Consider the following chemical reaction:

Magnesium + Oxygen --> Magnesium Oxide

     48.6 g   +   ? g     --> 80.6 g

How much oxygen (in grams) would be needed?

What is 32 grams?

500

When 0.0976 g of magnesium was heated in air, 0.1618 g of magnesium oxide (MgO) was produced.

(a) What is the percent of Mg in MgO?
(b) Using only law of definite proportions, what mass of oxygen was needed to combine with the magnesium?

(a) % Mg = (mass Mg / Mass MgO) 100

= (0.0976g / 0.1618 g) 100 = 60.3 %

(b) % O = 100% MgO – 60.3% Mg = 39.7% O

% O = (mass O / mass MgO) 100

39.7 %  = (mass O / 0.1618 g) 100

mass O = 0.397 ( 0.1618 g) = 0.0642 g O

Same as using the Law of Conservation of Mass.

Discoveries

100

Experiments in the late 1800s showed that cathode rays were composed of negatively charged particles. 

What is the discovery of the electron?

200

Robert A. Millikan's oil drop experiment measured what?

What is the charge of an electron?

300

The results of the gold foil experiment led to the discovery of a very densely packed bundle of matter with a positive electric charge. What did Rutherford call the positive bundle of matter?

What is the nucleus?

400

Joseph John Thomson's cathode-ray tube experiments measured what?

What is the charge-to-mass ratio of an electron?

500

What experiments led scientists to determine the mass of an electron?

What is the cathrode-ray tube experiments and the oil drop experiment?

Subatomic Particles

100

The smallest particle of an element that retains the chemical properties of that element. 

What is an atom?

200

A very small region located at the center of an atom.

What is the nucleus? 

300

The nucleus is made up of at least one positively charged particle and usually one of more neutral particles. What are the names of these two particles?

What is a proton and a neutron? 

400

Atoms are electrically neutral because they contain equal numbers of what?

What are protons and electrons?

500

The number of what subatomic particle determines that atom's identity?

What are protons?

Dimensional Analysis

100

How many miles will a person run during a 10 kilometer race?

(Hint:0.621 miles = 1 kilometer)

What is 6.21 miles?

200

The moon is 250,000 miles away. How many feet is it from Earth?

(Hint: 1 mile = 5280 feet)

What is 1,320,000,000 feet?

300

The average American student is in class 330 minutes per day. How many hours per day is this?

What is 5.5 hours per day?

400

Sixty miles per hour is how many feet per second?

(Hint: 1 mile = 5280 feet)

What is 88 feet per second?

500

Chicago uses 1.2x10⁹ gallons of water per day. How many gallons per second must be pumped from the lake every second to supply the city?

What is 13,889 gallons per second?

Counting Atoms

100

Atoms of the same element that have different masses due to the varying numbers of neutrons. 

What are isotopes?

200

This conversion factor is used to find the number of atoms of an element.

What is Avogadro's number?

300

What is the total number of protons and neutrons that make up the nucleus of an isotope?

What is the mass number?

400

How many moles are in 15 grams of lithium?

What is 2.2 moles of Li?

500

How many moles are there in 24.0 grams of FeF₃?

What is 0.213 moles?