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2.1 Class Work

Sample Question

Explanation of Answer

1. Which sequence represents a correct order of historical developments leading to the modern model of the atom

(1) the atom is a hard sphere most of the atom is empty space electrons exist in orbitals outside the nucleus

(2) the atom is a hard sphere electrons exist in orbitals outside the nucleus most of the atom is empty space

(3) most of the atom is empty space electrons exist in orbitals outside the nucleus most of the atom is empty space

(4) most of the atom is empty space the atom is a hard sphere electrons exist in orbitals outside the nucleus

KEY WORDS AND SYMBOLS:

EXPLANATION:

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2. Which statement correctly describes the charge of the nucleus and the charge of the electron cloud of an atom?

(1) The nucleus is positive and the electron cloud is positive.

(2) The nucleus is positive and the electron cloud is negative.

(3) The nucleus is negative and the electron cloud is positive.

(4) The nucleus is negative and the electron cloud is negative.


EXPLANATION:

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3. According to the wave-mechanical model of the atom, electrons in an atom

(1) are mostly likely found in the excited state

(2) have a positive charge

(3) are located in orbitals outside the nucleus

(4) travel in defined circles


EXPLANATION:

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2.1 Class Work

Directions: Answer all questions based on your knowledge of chemistry.

Part I: Write who discovered which model of atom

1. The first subatomic particle discovered was the

(1) proton(3) electron

(2) neutron(4) photon

2. Which group of atomic models is listed in historical order from earliest to the most recent?

(1) Hard-sphere model, wave-mechanical model, electron-shell model

(2) Hard-sphere model, electron-shell model, wave mechanical model

(3) Electron-shell model, wave-mechanical model, hard-sphere model

(4) Electron-shell model, hard-sphere model, wave-mechanical mode

3. Which phrase describes an atom?

(1) a positively charged electron cloud surrounding a positively charged nucleus

(2) a positively charged electron cloud surrounding a negatively charged nucleus

(3) a negatively charged electron cloud surrounding a positively charged nucleus

(4) a negatively charged electron cloud surrounding a negatively charged nucleus

4. The gold-foil experiment led scientists to conclude that an atom’s

(1) Positive charge is evenly spread throughout its volume

(2) Negative charge is mainly concentrated in its nucleus

(3) Mass is evenly spread throughout its volume

(4) Volume is mainly empty space

5. In Rutherford’s gold foil experiments, some alpha particles were deflected from their original paths but most passed with no deflection. Which statement about gold atoms is supported by these experimental observations?

(1) Gold atoms consist mostly of empty space.

(2) Gold atoms are similar to alpha particles.

(3) Alpha particles and gold nuclei have opposite charges

(4) Alpha particles are more dense than gold atoms.

6. The gold foil experiment led to the conclusion that each atom in the foil was composed mostly of empty space because most alpha particles directed at the foil

(1) Passed through the foil

(2) Remained trapped in the foil

(3) Were deflected by the nuclei in gold atoms

(4) Were deflected by the electrons in gold atom

2.1 Class Work

One model of the atom states that atoms are tiny particles composed of a uniform mixture of positive and negative charges. Scientists conducted an experiment where alpha particles were aimed at a thin layer of gold atoms.

Most of the alpha particles passed directly through the gold atoms. A few alpha particles were deflected from their straight-line paths. An illustration of the experiment is shown below.

a) Most of the alpha particles passed directly through the gold atoms undisturbed. What evidence does this suggest about the structure of gold atoms?’

b) A few of the alpha particles were deflected. What does this evidence suggest about the structure of the gold atoms?

c) How should the original model be revised based on the results of this experiment?

2.2 Class Work

Charge of Atom

· How many protons does this atom have? _______________

· How many electrons does this atom have? ______________

· How many neutrons does this atom have? ______________

· # of nucleons: ______________________

· Positive charge: __________ Negative charge: __________

· Overall charge: ________________________________

15 p

16 n

10 p

10 n

10 n

16 n

How many Protons? _________ How many Protons? _________

How many Electrons? _______ How many Electrons? _______

How many Neutrons? _______ How many Neutrons? _______

# of nucleons: __________ # of nucleons: __________

Positive charge: ___________ Positive charge: ___________

Negative charge: __________ Negative charge: __________

Overall charge: ___________ Overall charge: ___________

2.2 Class Work

SAMPLE QUESTION #1:

Which total mass is the smallest?

(1) the mass of 2 electrons

(2) the mass of 2 neutrons

(3) the mass of 1 electron plus the mass of 1 proton

(4) the mass of 1 neutron plus the mass of 1 electron

Let’s solve each multiple choice answer:

1. ____________________________________

2. ____________________________________

3. ____________________________________

4. ____________________________________

SAMPLE QUESTION #2: Base your answers on the information below:

In the modern model of the atom, each atom is composed of three major subatomic (or fundamental) particles.

a) Name the subatomic particles contained in the nucleus of the atom

b) State the charge associated with each type of subatomic particle contained in the nucleus of the atom.

c) What is the net charge of the nucleus?

2.2 Class Work

Answer the following questions

1. Which statement best describes electrons?

(1) They are positive subatomic particles and are found in the nucleus.

(2) They are positive subatomic particles and are found surrounding the nucleus.

(3) They are negative subatomic particles and are found in the nucleus.

(4) They are negative subatomic particles and are found surrounding the nucleus.

2. Which particles are found in the nucleus of an atom?

(1) electrons, only

(2) neutrons, only

(3) protons and electrons

(4) protons and neutrons

3. Which statement is true about the charges assigned to an electron and a proton?

(1) Both an electron and a proton are positive.

(2) An electron is negative and a proton is positive.

(3) An electron is positive and a proton is negative.

(4) Both an electron and a proton are negative.

4. Which statement is true about a proton and an electron?

(1) They have the same masses and the same charges.

(2) They have the same masses and different charges.

(3) They have different masses and the same charges.

(4) They have different masses and different charges.

5. Which subatomic particle will be attracted by a positively charged object?

(1) proton

(2) neutron

(3) electron

(4) positron

6. Which two particles have approximately the same mass?

(1) proton and neutron

(2) proton and electron

(3) neutron and electron

(4) neutron and positron

2.3 Class Work

Sample Question


Which sequence represents a correct order of What is the total number of neutrons in an atom of an element that has a mass number of 19 and an atomic number of 9?

(1) 9

(2) 19

(3) 10

(4) 28


EXPLANATION:

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A neutral atom contains 12 neutrons and 11 electrons. The number of protons in this atom is

(1) 1

(2) 11

(3) 12

(4) 23


EXPLANATION:

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What is the total number of electrons found in an atom of sulfur?

(1) 6

(2) 8

(3) 16

(4) 32


EXPLANATION:

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In which list are the elements arranged in order of increasing atomic mass?

(1) Cl, K, Ar

(2) Fe, Co, Ni

(3) Te, I, Xe

(4) Ne, F, Na


EXPLANATION:

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2.3 Class Work

Fill in the missing items in the table provided below.

Name of Element

Symbol of Element

Atomic #

Mass #

# Protons

# Electrons

# Neutrons

Na

17

Potassium

P

53

Silver

36

W

29

49

Practice Problems

1. How many protons and electrons are present in a vanadium atom?

2. How many protons, electrons, and neutrons are present in a platinum atom?

3. What is the name of the element that has atoms that contain 5 protons?

4. What is the name of the element that has atoms that contains 82 protons?

5. What is the atomic number of the element that has 74 protons? What is the name of that element?

2.3 Class Work

Sample Question


The nucleus of an atom of cobalt-58 contains

(1) 27 protons and 31 neutrons





EXPLANATION:

2. The nucleus of an atom of 42K contains






EXPLANATION:

Atoms of 16O, 17O, and 18O have the same number of

(1) neutrons but a different number of protons

(2) protons but a different number of neutrons

(3) protons but a different number of electrons

(4) electrons but a different number of protons


EXPLANATION:

Which symbols represent atoms that are isotopes of each other?

(1) 14C and 14 N

(2) 16O and 18 O

(3) 131 I and 131 I

(4) 222Rn and 222 Ra


EXPLANATION:

2.3 Class Work

For each of the following isotopes, write the number of protons, neutrons, and electrons as well as the other notation specified.

Nitrogen-15

Nitrogen-20

# of protons

# of electrons

# of neutrons

S-23

S-25

# of protons

# of electrons

# of neutrons

238 92 U

235 92 U

# of protons

# of electrons

# of neutrons

14N

12N

# of protons

# of electrons

# of neutrons

Describe, in terms of subatomic particles found in the nucleus, one difference between the nuclei of carbon- 12 atoms and the nuclei of carbon-13 atoms. The response must include both isotopes.

Describe, in terms of subatomic particles found in the nucleus, one difference between the nuclei of Chlorine-35 atoms and the nuclei of Chlorine-37 atoms. The response must include both isotopes.

DO NOT LEAVE CLASS WITHOUT YOUR DAILY TRACKER CHECKED! Date: _________________ Page 1

“Success is not the result of spontaneous combustion. You must set yourself on fire.”

2.4 Class Work

The accepted values for the atomic mass and percent natural abundance of each naturally occurring isotope of silicon are given in the data table below:

1. Show a correct numerical setup for calculating the atomic mass of Si

2. Determine the total number of neutrons in an atom of Si-29. ______________________________

· To find the average atomic mass, there are 3 simple steps:

Step 1: Determine Relative Natural Abundance

Formula: Percent Natural Abundance / 100

Step 2: Determine Relative Mass

Formula: Relative Natural Abundance x Mass Number

Step 3: Find Average Atomic Mass = Atomic Mass Number

Formula: ADD EACH RELATIVE MASS

2.4 Class Work

· Predict whether you think the answer will be closer to 63 or 65. Explain why.

· The atomic mass of copper is 63.546 amu. Which of copper’s two isotopes is more abundant: copper-63 or copper-65? Explain your reasoning.

· Calculate the atomic mass of copper:

2.4 Class Work

· Calculate the atomic mass. What whole number do you predict it to be close to?

PLEASE SOLVE THIS IN YOUR CORNELL NOTES AS A DOUBLE ENTRY JOURNAL

Naturally occurring elemental carbon is a mixture of isotopes. The percent composition of the two most abundant isotopes is listed below.

• 98.93% of the carbon atoms have a mass of 12.00 atomic mass units.

• 1.07% of the carbon atoms have a mass of 13.00 atomic mass units.

A. Describe, in terms of subatomic particles found in the nucleus, one difference between the nuclei of carbon-12 atoms and the nuclei of carbon-13 atoms. The response must include both isotopes.

B. In the space provided in your answer booklet, show a correct numerical setup for calculating the average atomic mass of carbon.

2.5 Class Work

PRACTICE simple electron configuration:

Write a ground state electron configuration for each neutral atom. Ground state means that all of the lowest possible energy levels (up to the proper number of electrons for the element) are filled. State how many energy levels each one has and number of electrons of those levels.

1. Na

2. Pb

3. Sr

4. U

5. N

6. Ag

7. Ti

8. Ce

9. Cl

10. Hg

Write the electron configuration for an atom that has 33 electrons.

Write the electron configuration for an atom that has 45 electrons.

2.5 Class Work

Do you see a pattern?

Element

Ground State

Excited State(s)

Carbon

2-4

2-3-1 or 1-5

Oxygen

2-6

2-5-1 or 1-7

Aluminum

2-8-3

2-7-4 or 2-8-2-1

1. Does the total number of electrons in an element change when the atom is in the ground state or the excited state?

2. How would you describe the difference between the ground state electron configuration and the excited state configuration?

3. Write one possible excited state configuration for F (fluorine).

Sample Question


Compared to a sodium atom in the ground state, a sodium atom in the excited state must have

A.) a greater number of electrons

B.) a smaller number of electrons

C.) an electron with greater energy

D.) an electron with less energy


EXPLANATION:

Which electron transition represents a gain of energy?

A.) from 2nd to 3rd shell

B.) from 2nd to 1st shell

C.) from 3rd to 2nd shell

D.) from 3rd to 1st shell


EXPLANATION:

2.5 Class Work

Sample Question


Which electron configuration represents the electrons of an atom in an excited state?

(1) 2-4

(2) 2-6

(3) 2-7-2

(4) 2-8-2


EXPLANATION:

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Which electron configuration represents an atom of chlorine in an excited state?

(1) 2-8-7

(2) 2-8-8

(3) 2-8-6-1

(4) 2-8-7-1


EXPLANATION:

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________________________________________________

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In comparison to an atom of F-19 in the ground state, an atom of C-12 in the ground state has

(1) three fewer neutrons

(2) three fewer electrons

(3) three more neutrons

(4) three more electrons


EXPLANATION:

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2.5 Class Work

Answer the following questions

What is the electron configuration of a sulfur atom in the ground state?

(1) 2-4 (2) 2-6 (3) 2-8-4 (4) 2-8-6

Which electron transition represents a gain of energy?

(1) from 2nd to 3rd shell (2) from 2nd to 1st shell

(3) from 3rd to 2nd shell (4) from 3rd to 1st shell

Which is an electron configuration for an atom of argon in the excited state?

(1) 2-8-7 (2) 2-8-8 (3) 2-8-6-1 (4) 2-8-7-1

Which electron configuration represents the electrons of an atom of oxygen in the ground state?

(1) 2-4 (2) 2-6 (3) 2-7-2 (4) 2-8-2

When compared with the energy of an electron in the first shell of a carbon atom, the energy of an electron in the second shell of a carbon atom is

(1) less (2) greater (3) the same

Which electron configuration represents the electrons of an atom in an excited state?

(1) 2–8–1 (2) 2–8–6 (3) 2–8–17–6 (4) 2–8–18–5

As an electron in an atom moves from the ground state to the excited state, the electron

(1) gains energy as it moves to a higher energy level

(2) gains energy as it moves to a lower energy level

(3) loses energy as it moves to a higher energy level

(4) loses energy as it moves to a lower energy level

2.5 Class Work

· Base your answer on the electron configuration table shown below.

a. Which electron configuration represents the excited state of a calcium atom?

b. What is the element Z?

· Write an appropriate number of electrons in each shell to represent an Mg-26 atom in an excited state. Your answer may include additional shells.

· Write an appropriate number of electrons in each shell to represent an N-14 atom in an excited state. Your answer may include additional shells.

Write an appropriate number of electrons in each shell to represent an Al-27 atom in an excited state. Your answer may include additional shells

2.6 Class Work

The valence electrons of a germanium atom in the ground state are located in the

A) first shell B) second shell

C) third shell D) fourth shell

Magnesium and calcium have similar chemical properties because a magnesium atom and a calcium atom have the same

A) atomic number

B) mass number

C) total number of electron shells

D) total number of valence electrons

Which set of symbols represents atoms with valence electrons in the same electron shell?

(1) Ba, Br, Bi

(2) Sr, Sn, I

(3) O, S, Te

(4) Mn, Hg, Cu

2.6 Class Work

Answer the following questions:

2.7 Class Work

How do neon lights work?

Adapted from http://www.herebeanswers.com/2011/07/how-do-neon-and-fluorescent-lights-work.html

Cool and colorful, eerily radiant, a neon tube emits a light of almost seductive elegance. But mesmerizing as their shimmer may be, neon system owe their glow to nothing more glamorous than a bit of gas and a jolt of electricity. Sealed within the glass tubing of, say, an illuminated signboard is a mixture of gases, one of which will always be neon. Left to itself, neon remains still and colorless. It is only when a current of electricity is passed through the gas that it reveals its garish talents.

When such an electrical change is applied, it stimulates electrons circling a neon atom’s nucleus. The suddenly excited electrons move farther away from the nucleus. This condition lasts only an instant. Almost immediately, the electrons return to their unexcited state, emitting a burst of energy that is visible, as a brilliant orange-red application of a coating of phosphor powder to the inside of the tube will yield commensurate changes in color.

1. Which subatomic particle plays a role in neon lights?

2. Describe what happens to this subatomic particle in order to produce neon lights?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Directions: Match up lines of elements we know to the unknown sample.

Which two elements are present in the unknown spectra below?

A.) Li & H

B.) Li & Na

C.) H & He

D.) Li & He

2.7 Class Work

Many advertising signs depend on the production of light emissions from gas-filled glass tubes that are subjected to a high-voltage source. When light emissions are passed through a spectroscope, bright-line spectra are produced.

Identify the two gases in the unknown mixture.

1. A and B

1. A and D

1. B and C

1. C and D

Given the bright-line spectra of three elements and the spectrum of a mixture formed from at least two of these elements:

Which elements are present in this mixture?

1. E and D, only

1. E and G, only

1. D and G, only

1. D, E, and G

2.7 Class Work

A glass tube is filled with hydrogen gas at low pressure. An electric current is passed through the gas, causing it to emit light. This light is passed through a prism to separate the light into the bright, colored lines of hydrogen’s visible spectrum. Each colored line corresponds to a particular wavelength of light. One of hydrogen’s spectral lines is red light with a wavelength of 656 nanometers. Tubes filled with other gases produce different bright-line spectra that are characteristic of each kind of gas. These spectra have been observed and recorded.

a) Explain, in terms of electron energy states and energy changes, how hydrogen’s brightline spectrum is produced. [1]

b) Explain how the elements present on the surface of a star can be identified using brightline spectra. [1]

c) A student measured the wavelength of hydrogen’s visible red spectral line to be 647 nanometers. In the space in your answer booklet, show a correct numerical setup for calculating the student’s percent error. [1]

Practice Regents Question

Identify all the elements in the mixture: _______________________________________________________________

“Success is not the result of spontaneous combustion. You must set yourself on fire.”

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