Chapter 1

Question 1

What three properties of electrons did JJ Thomson discover?

Answer 1

1. They travel in a straight line.
2. They are independent from the composition of the material from which they originate.
3. They carry a negative charge.

Question 2

Define electrostatic forces.

Answer 2

Electrostatic forces are the electrical charges of the particles that compose atoms that results in attractive and repulsive forces. These attractive and repulsive forces are called electrostatic forces.

Question 3

Describe Robert Millikan’s oil drop experiment.

Answer 3

Millikan wanted to measure the charge of a single electron. To do so, he sprayed fine droplets of oil through a small hole in a chamber he constructed. During their fall, the drops acquired electrons, which gave the droplets a negative charge. He then measured the strength of the electric field required to slow or halt the free fall of the negatively-charged oil droplets.

Question 4

What is the charge of a single electron?

Answer 4

-1.60 x 10^-19 C

Question 5

Describe the plum pudding model of the atom.

Answer 5

The plum pudding model states that there is a sphere of positive charge and within that sphere exists the electrons, which are like the plums in the pudding.

Question 6

Describe Rutherford’s gold foil experiment.

Answer 6

Rutherford performed the experiment in order to prove the plum pudding model of the atom. He projected a line of alpha particles at a thin gold foil sheet, thinking that they would pass straight through. Instead, some of the particles deflected, implying that the nucleus of an atom is not uniform.

Question 7

What are the three tenets of Rutherford’s nuclear theory?

Answer 7

1. Most of the atom’s mass and all of its positive charge are contained in a small core called the nucleus.
2. Most of the volume of the atom is empty space, in which are contained the tiny electrons randomly dispersed.
3. The atom is electrically neutral, meaning there are the same number of protons as there are electrons.

Question 8

Define amu.

Answer 8

Atomic mass unit. This is 1/12 the mass of a carbon atom containing six protons and six neutrons. The mass of a proton or neutron is about 1 amu.

Question 9

Define natural abundance.

Answer 9

Natural abundance refers to the frequency with which isotopes of elements appear naturally.

Question 10

Define mass number.

Answer 10

The sum of the number of protons and neutrons in an atom.

Question 11

Define cations.

Answer 11

Positively charged ions.

Question 12

Define anions.

Answer 12

Negatively charged ions.

Question 13

How is the atomic mass listed on the periodic table for an element calculated?

Answer 13

The atomic mass is calculated by averaging the weights of the different isotopes of the element and weighting them according to how frequently they occur.

Question 14

Briefly describe how a mass spectrometer works.

Answer 14

Atoms are converted to positively charged ions, accelerated, and passed through a magnetic field that deflects their path. The heaviest ions undergo the least deflection, allowing scientists to determine the mass of the atoms.

Question 15

Define mole.

Answer 15

A mole is the amount of material containing 6.02214 x 10^23 particles (this is Avogadro’s number).

Question 16

How did the mole get its specific value?

Answer 16

The value of the mole is equal to the number of atoms in exactly 12 g of pure carbon-12.

Question 17

Define molar mass.

Answer 17

Molar mass is the mass of 1 mol of atoms of a given element.

Question 18

What is mass spectrometry?

Answer 18

An analytical technique that detects the mass-to-charge ratio of an analyte.