Chemistry

Atoms

Learning Objectives Atoms

Essential knowledge and skills:

Determine the atomic number, atomic mass, the number of protons, and the number of electrons of any atom of a particular element using a periodic table.

Determine the number of neutrons in an isotope given its mass number. Perform calculations to determine the “weighted” average atomic mass. Perform calculations involving the half-life of a radioactive substance. Differentiate between alpha, beta, and gamma radiation with respect to penetrating power, shielding, and composition. Differentiate between the major atom components (proton, neutron and

electron) in terms of location, size, and charge. Identify key contributions of principal scientists including:o atomos, initial idea of atom – Democrituso first atomic theory of matter, solid sphere model – John Daltono discovery of the electron using the cathode ray tube experiment, plum pudding model – J. J. Thomsono discovery of the nucleus using the gold foil experiment, nuclear model – Ernest Rutherfordo discovery of charge of electron using the oil drop experiment – Robert Millikano energy levels, planetary model – Niels Bohro periodic table arranged by atomic mass – Dmitri Mendeleevo periodic table arranged by atomic number – Henry Moseleyo quantum nature of energy – Max Plancko uncertainty principle, quantum mechanical model – Werner Heisenbergo wave theory, quantum mechanical model – Louis de Broglie. Differentiate between the historical and quantum models of the atom.

Essential understandings:

The periodic table is arranged in order of increasing atomic numbers. The atomic number of an element is the same as the number of protons. In a neutral atom, the number of electrons is

the same as the number of protons. All atoms of an element have the same number of protons. The average atomic mass for each element is the weighted average of that element’s naturally occurring isotopes. The mass number of an element is the sum of the number of protons and neutrons. It is different for each element’s

isotopes. An isotope is an atom that has the same number of protons as another atom of the same element but has a different

number of neutrons. Some isotopes are radioactive; many are not. Half-life is the length of time required for half of a given sample of a radioactive isotope to decay. Electrons have little mass and a negative (–) charge. They are located in electron clouds or probability clouds outside

the nucleus. Protons have a positive (+) charge. Neutrons have no charge. Protons and neutrons are located in the nucleus of the

atom and comprise most of its mass. Quarks are also located in the nucleus of the atom. Discoveries and insights related to the atom’s structure have changed\ the model of the atom over time. Historical

models have included solid sphere, plum pudding, nuclear, and planetary models. The modern atomic theory is called the quantum mechanical model.

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History of the Atom (find answers from Power point in VISION)

Democritus proposed: _______________________________________________________________

These “particles” were thought to be indivisible

Which person did not accept Democritus’ atom, he was of the “_______________ ________________”

philosophy

Because of Aristotle’s popularity his theory was adopted as the standard

By the 1700’s nearly all chemists had accepted the modern definition of an element as a

__________________________________________.

It was also understood at that time that _______________________________

____________________________________________________________ However, these understandings

were based on ______________________ not ______________________ (empirical = comes from

observation)

There was controversy as to whether elements always combine in the same proportion when forming a

particular compound.

In the 1790’s, chemistry was revolutionized by a new emphasis ____________________ because of new and

improved ________________.

This new technology led to the discovery of some new scientific understandings

The ___________________________________________:

Proposed by Antoine Lavoisier

States that

Which means the _______________________________________________

The _______________________________:

The fact that a _______________________________________

______________________________________________________________________________________

______________________

Ex: ________, _________, _________, _______

Atomic Theory:

In 1808, John Dalton proposed an explanation for each of the proposed laws

He reasoned that ___________________________________________

_________________________________________________________

His ideas are now called the __________________________________

All matter is composed of extremely small particles called _________

Atoms of a given element are identical in ________, _______, and other properties; atoms of

______________ elements differ in size, mass, & other properties

Atoms cannot be __________________, _________________, or________________

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Atoms of different elements combine in simple __________________________ to form chemical

compounds

In chemical reactions, atoms are _____________, _____________, ____________________.

Through these statements, evidence could be gathered to confirm or discount its claims

Not all of Dalton’s claims held up to the scrutiny of experimentation

Atoms _________ be divided into even smaller particles

Not every atom of an element has an _____________.

Ex:

Dalton’s Atomic Theory of Matter has been modified.

What remains is:

___________________________________________________________________________

___________________________________________________________________________

One of the disputed statements of Dalton was that atoms are ________ indivisible

In the 1800’s it was determined that

__________________________________________________________ like

_____________________________________________________________________

It’s the _______________ and ________________ of these particles that determine the atom’s chemical

properties.

The definition of an atom that emerged was:

______________________________________________________________________________________

__________________________________________________________

Structure of an Atom

All atoms consist of 2 regions that contain the subatomic particles

________________________________________________________________

________________________________________________________________

The nucleus is a very small region located near the center of the atom

In every atom the nucleus contains at least 1 _________, which is _________________ charged particle

and usually contains 1 or more _______ particles called __________.

The electron cloud is the region that surrounds the nucleus

This region contains 1 or more _______________, which are _______________ charged subatomic

particles

The volume of the electron cloud is ____________________ than the nucleus

Discovering the Electron

The discovery of the first subatomic particle took place in the late 1800’s.

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A power source was attached to two metal ends of an evacuated glass tube, called a

______________________________.

A beam of “light” appears between the two electrodes called a _________________

Investigators began to study the ray and they observed that…

An object placed in the path of the ray cast a shadow on the glass

Cathode rays were _________________________________________

The rays were deflected away from a __________________________.

The first 2 observations support the idea that the ray is composed of ________

_______________________________________________________________

The second set of observations support the evidence that the ray is composed of a

_________________________________________________________________.

J.J. Thomson studied the rays with cathode tube and proved that they were

____________________________ being emitted from the metal atoms. Dubbed these tiny particles

“___________”

Devised the________________________ Model

Each atom was a sphere filled with a _________________________. The fluid was called the "______."

Scattered in this fluid were __________ known as the "_________."

Robert Millikan then used an ingenious investigation to calculate

___________________________________________________________________

In his Oil Drop Experiment, he determined that

______________________________________________

Charge of Electron= ______________________________

Mass of Electron = _______________________________

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What can their work help us conclude about the atom?

atoms are composed of smaller particles, and one of these components is

________________________________

atoms are neutral, so there must be an opposing _____________________

because electrons are essentially mass-less, there must be an

__________________________________________________________________

Discovering the Neutron

In 1932, the English physicist James Chadwick discovered yet another subatomic particle.

– the ____________________ is electrically neutral

– It’s mass is nearly _________________as that of the proton

New Structure of Atoms

In 1911, Ernest Rutherford et al. provided a more detailed picture of the internal structure of the atom

Gold Foil Experiment: In his experiment, Rutherford directed a narrow beam of __________________

at a very thin sheet of ______________.

Alpha particles (α) are _______________________________________.

According to Thomson’s model, the heavy, positive alpha particles

______________________________________________________________________________________

__________________________________________________________

However, Rutherford found _________________________________________________

________________________________________________________________________

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Rutherford suggested a new structural model of the atom.

He stated that ________________________________________

___________________________________________________

And that the atom is mostly ____________________________.

___________________________________________________ like planets around the sun.

Rutherford’s planet system model was an improvement over earlier models, but it was still not complete.

Physics says that _________________________________________

_______________________________________________________

Losing energy would cause the electron to spiral into the nucleus.

The attraction of the electron to the nucleus would cause it to spiral into the nucleus as well

Niels Bohr proposed a new model that would allow the _______________________________________

and _________________________

____________________________________________________________________.

His model coupled Rutherford’s model with a new concept of energy in Physics called

_____________________________________________________________________

Bohr proposed that the electrons aren’t on any random orbit around the nucleus, they are on

_________________.

Bohr’s Model restricts the orbits on which an electron can be found

The bases for what orbit an electron is allowed is entirely based on

_________________________________________

If it has any more energy or any less energy it would be forced to be on a different path of different energy

Each path or level of energy that the electron is on is given a label of “n”

Such that n=1 is the closest energy level to the nucleus

Each energy level can only hold a certain number of electrons (2n2)

n=1 can hold ____ electrons

n=2 can only hold ____ electrons

n=3 can hold ____ electrons

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Summary of the main ideas in chronological oder

NAME CONTRIBUTION MODEL OR EXPERIMENT

JOHN DALTON

Atomic Theory:

1. All matter is made of atoms (atoms are indivisible and indestructible)

2. All atoms in an element are identical to each other in mass and properties

3. Compounds are formed by a combination of 2 or more different kinds of atoms in different ratios

4. A chemical reaction is a rearrangement of atoms

5. In reactions, matter is neither created or destroyed (law of conservation of matter)

Solid Sphere – “Billiard Ball Model”

-different atoms were drawn at different sizes

Discovered electrons

- Negative electrons set in a sponge of

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J. J. THOMSON

Used cathode rays to show how electrons were deflected by magnetic forces

“+” charge

-“Plum Pudding” Model

ERNEST RUTHERFORD

Gold Foil experiment – proved nuclear form

Discovered a positively charged nucleus (99.9% of mass of atom)

Atoms are mostly made up of empty space

-“Nuclear” Model-Protons in nucleus with electrons floating outside nucleus

NIELS BOHR Discovered electron motion

Said that electrons orbit around the nucleus

Light emissions

- “Solar System” Model

Subatomic Particles

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In ancient times, people believed that all matter is a variation of earth, air, fire and water. Until early 20th century people believed that the basic building block of matter is an atom, visualized as a sphere. Nowadays, we know that atoms are made of even more fundamental entities. The diagram below shows an increasing magnification of an imaginary microscope on an ordinary matter.

For a given atom, it is consisted of a nucleus occupies a very small volume of space, and a collection of electrons that are attracted to the nucleus by electromagnetic forces. The lump is called the nucleus of an atom while the extension of electrons in space defines the size of an atom. The more number of electrons the larger the size of the atom. Electrons are incredibly small. No one knows the actual size, but it is estimated at the lower scale of 10-18 m, almost a point-like. Electrons are one of the most fundamental particles. In other words, they are not made of anything smaller (so we think).

However, the nucleus is made of a mixture of protons and neutrons. The size of a proton and a neutron are similar, in the order of 10-15 m. We now know that they are not the fundamental particles. Take, for example, a proton. It is now believed a proton is made of three fundamental particles called quarks. There are six different types of quarks, of which only up (u) quark and down (d) quark made up of protons: 2 up and 1 down. This is often written as 'duu'. On the other hand, a neutron is made of 'ddu': two down quarks and one up quark. Once again, to our current understanding, a quark is a fundamental particle. These quarks are held very tightly by the strong force carrier called gluon.

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The Strong force

This force acts between quarks. Its operation involves the exchange of particles called gluons (which are neither quarks nor leptons).

• The force does its work in a very short time (~ 10-23s), so can bring about interactions between particles colliding at high kinetic energies (and close to each other for only very short times).

The Weak force

Both quarks and leptons can ‘feel’ the weak force. It is involved in certain decays and interactions, and its involvement – in all common cases – is signalled by

interaction times in the order of 10-12 s or longer neutrino (or antineutrino) involvement change of quark flavour (that is u number and d number are not conserved)

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The Electromagnetic force

This acts between all charged particles and is signalled by photon emission or absorption. It may be involved in the internal re-arrangement of, for example, quarks within a hadron, or electrons within an atom. Some particle-antiparticle annihilations occur via this force. A typical interaction time would be 10-17s.

Summary Table

Sub Atomic Particle

Mass (kg) Relative Atomic Mass (amu)

Charge (C) Relative charge (C)

Where?

Proton 1.672 x 10-27 1 1.60 x 10-19 +1 nucleusNeutron 1.675 x 10-27 1 0 0 nucleusElectron 9.109 x 10-31 1/1840 -1.60 x 10-19 -1 clouds

Distinguishing Between Atoms

Atomic Number

Elements are different because they contain different numbers of protons The atomic number of an element is the number of protons in the nucleus

o Atomic number identifies an elemento Since atoms are neutral, number of protons = number of electrons o The number of protons never changes for an elemento The number of electrons might change for an element (forms an ion)o Elements on the periodic table are organized according to increasing atomic number, or increasing

number of protons

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Mass Number

Total number of protons and neutrons in an atom is called the mass number Number of neutrons can be determined by

o Number of neutrons = mass number – atomic number Shorthand notation for an element

X = Element symbol from the periodic table

A = Mass Number (p + n)

Z = Atomic Number (p)

Usually abbreviate the names of the element by saying the name of the element followed by its atomic mass, “carbon-12.”

Isotopes

Isotopes are atoms of the same element that have different masses. The number of protons and electrons is the same for all isotopes of an element, but the number of neutrons is different, causing each isotope to have a different atomic mass. Atomic number does not change.

o Hydrogen-1 has no neutrons, mass number of 1o Hydrogen-2 (deuterium) has one neutron, mass number of 2o Hydrogen-3 (tritium) has two neutrons, mass number of 3

Isotopes are chemically alike because they have identical numbers of protons and electrons which are the subatomic particles responsible for chemical behavior

Why can there be more than one possible number of neutrons in an atom? For many atoms, there can be several different numbers of neutrons that serve to stabilize the positive charge in the nucleus.

Atomic Mass or Atomic Weight

Atomic mass is measured in atomic mass units (amu), defined as 1/12 the mass of a carbon-12 atom. (Carbon-12 is the standard reference.)

1 amu = 1.67 x 10-27 kg Atomic mass is not always a whole number because of the relative abundance of the naturally occurring

isotopes of the element. Most elements occur as a mixture of two or more isotopes Each isotope of an element has a fixed mass and natural percent abundance The atomic mass of an element is the weighted average mass of the atoms in a naturally occurring sample of

the element. How to calculate atomic mass:

o Need the number of stable isotopes of the elemento The mass of each isotopeo The natural percent abundance of each isotope

Example:

Chlorine-35 occurs 75.77% (34.969 amu)

Chlorine-37 occurs 24.23% (36.966 amu)

Convert percentages into decimals (75.77% = 0.7577)

(0.7577 x 34.969) + (0.2423 x 36.966) = 35.453 amu

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Closer to the mass of Chlorine-35 since that’s the more abundant isotope. Note the correct number of significant figures.

Atoms

The number of protons in an atom determines the identity of the atom. Atomic number = number of Protons In a neutral atom, the number of positive protons equals the number of negative electrons. Protons and neutrons both have a mass of 1 amu. The mass of the electron is negligible compared to the mass

of the proton and neutron. Thus the mass number, or the mass of the atom, is the sum of the number of protons and neutrons. Mass number = number of Protons + number of Neutrons

Name Symbol Atomic # Mass # # Protons # Neutrons # Electrons

Selenium 46

222 86

118 79

11 12

Isotopes

The number of neutrons in any specific type of atom can vary. Atoms of the same element with different numbers of neutrons are called isotopes.

Isotopes are distinguished from each other by including the mass number with the name or symbol. Name Symbol Atomic # Mass # # Protons # Neutrons # Electrons

235U

238U

Carbon-12

Carbon-13

Ions

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As we have seen, in a neutral atom, the number of protons and the number of electrons is equal. Atoms can gain or lose electrons to become ions. Ions are charged atoms resulting from the difference in

number of positive protons and negative electrons. A cation is a positive ion. A cation results when an atom loses electrons. Number of Protons > Number of

Electrons An anion is a negative ion. An anion results when an atom gains electrons. Number of Electrons > Number of

Protons Ions are distinguished from atoms by including the ion charge as a superscript in the symbol.

Name Symbol Atomic # Mass # # Protons # Neutrons # Electrons Cation or Anion?

Al3+ 14

Ferric Ion 56 23

15 15 18

F- 19

I S O T O P E S & A V E R A G E A T O M I C M A S S

1. What is the average atomic mass of silicon if 92.21 % of its atoms have a mass of 27.977 amu, 4.07 % have a mass of 28.976 amu, and 3.09 % have a mass of 29.974 amu?

2. Calculate the average atomic mass for neon if its abundance in nature is 90.5% neon-20 (19.922 amu), 0.3% neon-21 (20.994 amu), and 9.2% neon-22 (21.991 amu).

3. Calculate the average atomic mass of chromium.Isotope Mass (amu) Relative Abundance

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Chromium – 50 49.946 0.043500Chromium – 52 51.941 0.83800Chromium – 53 52.941 0.095000Chromium – 54 53.939 0.023500

4. Which of the following are isotopes of element X, with atomic number of 9? (Circle)

, , ,

5. The element Eu occurs naturally as a mixture of 47.82% 151Eu, whose mass is 150.9 amu and 52.18% 153Eu, whose mass is 152.9 amu. Calculate the average atomic mass of Eu.

Atomic Structure Review

The table below contains information about several elements. In each case, enough information has been provided for you to fill in the blanks. Assume all atoms are neutral.

Isotope name Nuclear Symbol

Atomic Number

Mass Number

# of Protons

# of Electrons

# of Neutrons

6. calcium-40

7. 12 24

8. 1 2

9.

10. 26 30

11. 201 80

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12. 17 18

1. Please use the following table to calculate the average atomic mass of chlorine. Correct significant digits required.

Isotope % Abundance Mass (amu)

35Cl 75.78% 34.969

37Cl 24.22% 36.966

2. Raiderium (Cv) has three naturally occurring isotopes. Raiderium is 74.655% 44Cv, which has an atomic mass of 43.064 amu, 24.958% 46Cv, which has a mass of 46.125 amu, and 0.387% 48Cv, which has an atomic mass of 47.982 amu. Please calculate the average atomic mass of Raiderium to the correct number of significant digits.

Type of radiation

Charge Mass Nature Symbol Deflection in magnetic or

Relative penetration

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g mol-1 electric fields power

Alpha radiation

(α particle)

+2 4 2 protons

2 neutrons

helium nucleus

He24

α24

Some deflection towards negative plate

Paper or a few centimetres of air

Beta radiation

(β particle)

-1 1/1840 high energy electron

β−10

e−10

Large deflection towards positive plate

Aluminium plate 1-2 cm thick

Gamma radiation

( rays)

0 0 Short wavelength electromagnetic radiation

No deflection Lead 1 cm thick

or 2 m of concrete

Nuclear Chemistry: Types of Ionising Radiation

Zone of Stability

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Decay Series

Balancing Nuclear equations

The mass number and atomic number on either side of the reaction arrow must balance (conservation of mass). Use your periodic table to find the missing element/sub-atomic particle

Rn → + He24

86222

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→ Th + α24

90234

Th → Ra + 88226

90230

Pb → + e−10

82214

U → Np + 93234

92234

Write a balanced nuclear equation for the Beta decay of:

Nitrogen-16

Potassium-40

Write a balanced nuclear equation for the Alpha decay of:

Plutonium-244

Strontium-90

1. Complete the following reactions:Cl→ e+?+1

01739

Si→?+ P+ n01

1525

1426

Ra → ?+ α24

88226

? → 2 n+ U92236

01

2. Write correct nuclear equations for each of the following:

a. alpha () decay of thorium-232

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b. positron (ß+ ) decay of zinc-65

c. beta ( ß- ) decay of copper-64

d. electron-capture of potassium-40 (a “beta” particle being added as a reactant)

e. gamma decay of barium-137

3. Complete the following nuclear equations. In each case write which type of decay is occurring.

Fission and Fusion

Half-Life Calculations

The definition for half-life is the time required for half the original amount of substance to decay. This can be mass or radiation count. In this unit we will only use whole number half-lives.

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Number of Half-lives Fraction remaining % remaining0 1001 1/2 502 1/4 (1/2 x 1/2) 253 1/8 (1/2 x ½ x ½ ) 12.54 1/16 (1/2 x ½ x ½ x ½ ) 6.255 ? ?

1. Barium-139 has a half-life of 86 minutes. Suppose you have a 17.8-gram sample of barium-139. How much of the sample remains unchanged after 5 hours and 44 minutes?

2. A sample of cobalt-60 has a half-life of 5.26 years. If 98 grams of this radioisotope remain unchanged after approximately 15.78 years, what was the mass of the original sample?

3. After one year and 124 days, approximately 150 grams of a sample of calcium-45 remain unchanged. If the original sample had a mass of 1200 grams, what is the half-life of calcium-45? [The half-life will be in days.]

4. Phosphorus-33 has a half-life of 25.4 days. Suppose you have a 46.8- gram sample of phosphorus-33. How much of the sample remains unchanged after 101.6 days?

More half-life Problems

How much of a 100.0 gram sample of gold-198 is left after 8.10 days if its half-life is 2.70 days?

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A 50.0 grams sample of nitrogen-16 decays to 12.5 grams in 14.4 seconds. What is its half-life?

The half-life of potassium-42 is 12.4 hours. How much of a 728 gram sample is left after 62.0 hours?

What is the half-life of technetium-99 if a 500.0 gram sample decays to 62.5 grams in 639,000 years?

The half-life of thorium-232 is 1.4 x 1010 years. If there are 25.0 grams of the sample left after 2.8 x 1010 years, how many grams were in the original sample?

There are 5.0 grams of iodine-131 left after 40.35 days. How many grams were in the original sample if its half-life is 8.07 days?

Review Questions:

1) Write the nuclear transformation reaction for the alpha decay of radon-198

2) Write the nuclear transformation reaction for the beta decay of uranium-237

3) Write the nuclear transformation reaction for the Positron emission from silicon-26

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4) Write the nuclear transformation reaction for Sodium-22 undergoing electron capture

5) Plutonium-239 has a half life of 2.41x104 yr. If you have a 1.00 mg sample how much will remain after 4 half-lives have passed?

6) The half-life of 95Am241 is 458 years. How much of a 12.0 g sample would remain after 1375 years?

THE NUCLEAR FISSION REACTORThe reactor is a way of getting energy from the uranium fission in a controlled way. The first nuclear fission reactor was made by Enrico Fermi in a squash court in Chicago in 1942.One form of fission reactor is shown in the diagram.

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The CORE of the reactor contains the uranium fuel (an alpha emitter and not very dangerous if handled with care) that is held in thousands of metal tubes in a large block of graphite. The graphite, called the MODERATOR slows down the neutrons emitted at each fission so that they can react better. Carbon dioxide gas is blown through the reactor core under pressure to take away the heat energy produced by the fission reactor. This gas is then passed over tubes containing water, giving out its heat and turning the water into high temperature steam which is then used to drive turbines and generators. To increase or decrease the output power of the reactor a large number of CONTROL RODS are used. These are made of boron or boron-steel that gobble up neutrons. They can be lowered into the reactor to reduce the number of neutrons and so lower the power or they can be raised to increase the power.

When the nucleus splits we get two smaller nuclei, two or three neutrons and some energy. This energy appears as heat due to the kinetic energy of the smaller nuclei and the neutrons.The energy is produced because the mass of the uranium nucleus plus the mass of the incoming neutron is slightly greater than the masses of the particles formed after fission.

You don't get very much energy from splitting one uranium nucleus but in one kilogram of uranium there are around a million million million million million nuclei and if you could split all of them the energy produced would be very large. In fact if all the nuclei in 1 kg of uranium 235 could be split the energy produced would be about the same as that obtained from burning three thousand tons of coal!

The whole reactor core is contained in a steel pressure vessel and then surrounded by a thick layer of concrete to protect the workers from radiation.

The reactor is a very heavy structure and so it is important that nuclear power stations are built on very stable solid rock. They need large amounts of water to turn to steam to drive the turbines and also as coolant in the condensing units and so they should be built near the sea, a river estuary or a large lake.People are not usually too happy about living near a nuclear reactor and so nuclear power stations are usually built in areas of low population.

Benefits and drawbacks of nuclear power

(a) benefits(i) low or zero carbon dioxide emission(ii) relatively large uranium fuel reserves

(b) drawbacks(i) expensive to build(ii) radiation danger during operation(iii) danger of terrorist attack(iv) disposal of radioactive nuclear waste

Nuclear waste

Low level waste: This is gloves, cast off clothing, over shoes etc.

Intermediate level waste: This is fuel containers

High level waste: This is mainly irradiated fuel taken from reactors.

Questions:

1. This is a diagram of a typical nuclear reactor.

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(i) Which part of the reactor is designed to control the rate of nuclear fission?

(ii) The moderator slows down the neutrons. Why do they need slowing down?

Useful Radioisotopes

Radioactive isotopes can be very useful. They are used in:

1. Medicine for both treatment and diagnosis2. Archaeological and geological dating using carbon-14 or uranium3. Fluid flow measurement - water, blood, mud, sewage etc.4. Thickness testing of materials such as polythene 5. Radiographs of metal castings6. Sterilisation of food and insects7. Tracers in fertilisers used in agriculture8. Smoke alarms in houses9. Tracing phosphate fertilisers using phosphorus-3210. Checking the silver content of coins11. Atomic lights using krypton-8512. Testing for leaks in pipes

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Oxidation Numbers

Redox Reactions - Practice Problems - Determining Oxidation Numbers

1. Determine the oxidation number of each element in the following compounds.

Oxidation Numbers for each Element

a. SnCl4 Sn Cl

b. Ca3P2 Ca P

c. SnO Sn O

d. Ag2S Ag S

e. HI H I

f. N2H4 N H

g. Al2O3 Al O

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h. S8 S

i. HNO2 H N O

j. O2 O

k. H3O+ H O

l. ClO3- Cl O

m. S2O32- S O

n. KMnO4 K Mn O

o. (NH4)2SO4 N H S O

2. Determine the oxidation number of carbon in each of the following compounds:

a. methane, CH4 b. formaldehyde, CH2O

c. carbon monoxide, CO d. carbon dioxide, CO2

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