Chapter 3 hw

In 1909, Robert Millikan performed an experiment involving tiny, charged drops of oil. The drops were charged because they had picked up extra electrons. Millikan was able to measure the charge on each drop in coulombs. Here is an example of what his data may have looked like.

Based on the given data, how many extra electrons did drop C contain?

A 3.20times 10^{-19}
B 4.80times 10^{-19}
C 8.00times 10^{-19}
D 9.60times 10^{-19}

5 electrons

Why did different drops have different charges?
Because some drops had picked up more electrons than others.

What did each of the following scientists contribute to our knowledge of the atom?

James Chadwick
Michael Faraday
Eugen Goldstein
J.J Thomson
William Crookes
Ernest Rutherford

Chadwick- discovered the neutron.
Faraday- developed electrolysis.
Goldstein- discovered the proton.
Thomson- discovered the electron.
Crookes- developed the cathode ray tube.
Rutherford- proposed the nuclear theory of the atom.

What is radioactivity?
Radioactivity is spontaneous radiation from an atomic nucleus.

How did the discovery of radioactivity contradict Dalton’s atomic theory?
Dalton’s Atomic theory stated that atoms were indestructible.

Unstable atomic nuclei decay to form nuclei that are usually more stable. In the process, they emit high-energy particles. These particles, called nuclear radiation, occur in three different forms:
alpha (α) particles,
beta (β) particles, and
gamma (γ) rays.
Alpha particles are helium nuclei, with two neutrons and two protons. Beta particles are high-energy electrons. Gamma rays are high-energy photons, a form of electromagnetic radiation just like visible light but of much higher energy.

Match each description to a type of radiation.

charge =+2 A particle

charge = -1 B particle

least penetration A particle

mass =0 amu Y ray

medium penetration B particle

deepest penetration Y ray

mass~1/2000 amu B particle

mass~4 amu A particle

charge = 0 Y ray

Rank the following by speed.
1.alpha (α ) particles,
2.beta (β ) particles, and
3.gamma (γ ) rays.
Fastest

gamma
beta
alpha

slowest

Which is the charge of an alpha particle?
+2

Conclusions from Rutherford’s experiment
Watch the animation depicting Rutherford’s experiment and choose which of the following conclusions are correct.

1. A positive charge is condensed in one location within the atom.

2. A positive charge is spread equally over the atom.

3. The atom is a very compact entity without any empty space.

4. The atom does not have a positive charge.

5. The majority of the space inside the atom is empty space.

1. A positive charge is condensed in one location within the atom.

5. The majority of the space inside the atom is empty space.

The structure of the atom
On the basis of Rutherford’s experimental observations, which of the following statements predicts the structure of the atom?

1. In an atom, negatively charged electrons are small particles held within a positively charged sphere.

2. In an atom, negatively charged electrons are dispersed in the space surrounding the positively charged nucleus of an atom.

3. In an atom, all of the positive and negative charges are randomly distributed.

4. In an atom, most of the mass and the positive charge are located in a small core within the atom called the nucleus.

2. In an atom, negatively charged electrons are dispersed in the space surrounding the positively charged nucleus of an atom.

4. In an atom, most of the mass and the positive charge are located in a small core within the atom called the nucleus.

Sort each of the items into the appropriate bin. Use the diagram of a neutral lithium atom, shown to the left, for reference.(Figure 1)
Drag each item to the appropriate bin.
Proton:
Particle labeled “B”
+1 charge
approximately the same mass as a neutron

Neutron:
Particle labeled “A”
no charge

Electron:
Particle labeled “C”
-1 charge
smallest mass of the three particles

In Rutherford’s model of the atom, where are the protons, the neutrons, and the electrons found?
in the nucleus:
protons, nutrons

surrounding the nucleus:
electrons

The following table describes four atoms.
Atom A Atom B Atom C Atom D
Number of protons 20 21 21 20
Number of neutrons 21 20 21 20
Number of electrons 20 21 21 20
Are atoms A and B isotopes? No
Are atoms A and C isotopes? No
Are atoms A and D isotopes? Yes
Are atoms B and C isotopes? Yes
Are atoms C and D isotopes? No

Which two atoms in the table have about the same mass?
Atom A Atom B Atom C Atom D
Number of protons 17 18 18 17
Number of neutrons 18 17 18 17
Number of electrons 17 18 18 17
4. A and B

*the atomic number is the number of protons in an element, while the mass number is the number of protons plus the number of neutrons.

How many different isotopes of silver are listed here? (The X does not necessarily represent any specific element.)
108/47 X 108/48 X 110/47 X 107/47 X
3 isotopes

* in the example you can see that element with atomic number 47, but different mass numbers 108,109,107 are isotopes.

How many protons and neutrons are there in a
34 S
16
nucleus?

1. 34 neutrons and 16 protons
2. 18 protons and 16 neutrons
3. 18 neutrons and 16 protons
4. 50 neutrons and 16 protons

3. 18 neutrons and 16 protons

*34 is the mass
16 is the atomic number/ protons
subtract 34-16=18

What theory uses wave properties to describe the motion of particles at the atomic and subatomic levels?

1. the Dalton model
2. the quantum mechanical model
3. the Bohr model
4. the electrolysis mode

2. the quantum mechanical model

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