Chapter 3Chapter 3

Atoms: The Building Blocks of Matter

Atoms: The Building Blocks of Matter

The Atomic TheoryThe Atomic Theory

Law of conservation of mass Mass is neither destroyed nor created

Law of definite proportions Compound is always composed of

same proportion of elements Law of multiple proportions

If two different compounds are composed of the same elements, the two elements form a ratio of small number

Law of conservation of mass Mass is neither destroyed nor created

Law of definite proportions Compound is always composed of

same proportion of elements Law of multiple proportions

If two different compounds are composed of the same elements, the two elements form a ratio of small number

Law of Conservation of Mass

Law of Conservation of Mass

Law of Multiple Proportions

Law of Multiple Proportions

DaltonDalton

All matter is composed of atoms Atoms of an element are identical

in size, mass and other properties Atoms cannot be subdivided,

created, or destroyed Atoms combine in simple whole-

number ratios Atoms are combined, separated, or

rearranged in chemical reactions

All matter is composed of atoms Atoms of an element are identical

in size, mass and other properties Atoms cannot be subdivided,

created, or destroyed Atoms combine in simple whole-

number ratios Atoms are combined, separated, or

rearranged in chemical reactions

Modern Atomic TheoryModern Atomic Theory

All matter is composed of atoms Atoms of one element differ in

properties from atoms of another element

Atom - smallest particle of an element that retains the chemical properties of that element

All matter is composed of atoms Atoms of one element differ in

properties from atoms of another element

Atom - smallest particle of an element that retains the chemical properties of that element

ThompsonThompson

Current passed through cathode-ray tube

Current produced a stream of particles (cathode ray) that traveled towards the anode

Rays deflected from negatively charged object

Ratio of charge to mass of particles

Current passed through cathode-ray tube

Current produced a stream of particles (cathode ray) that traveled towards the anode

Rays deflected from negatively charged object

Ratio of charge to mass of particles

MilikanMilikan

Oil-drop experiment Charge of electron determined Calculated mass of electron using

ratio of charge to mass

Oil-drop experiment Charge of electron determined Calculated mass of electron using

ratio of charge to mass

The ElectronThe Electron

Mass of 9.109 x 10-31 kg Atoms are neutral, so must contain

same number of electrons and protons

Electrons mass has negligible effect on total mass of atom

Mass of 9.109 x 10-31 kg Atoms are neutral, so must contain

same number of electrons and protons

Electrons mass has negligible effect on total mass of atom

The NucleusThe Nucleus

Rutherford’s gold foil experiment Thin, gold foil bombarded with α

particles Some α particles deflected Caused by positively charged nucleus Volume of nucleus small

Rutherford’s gold foil experiment Thin, gold foil bombarded with α

particles Some α particles deflected Caused by positively charged nucleus Volume of nucleus small

RutherfordRutherford

RutherfordRutherford

The NucleusThe Nucleus

Composed of two particles Protons Neutrons

Protons mass = 1.673 x 10-27 kg 1826 times greater than e-

Nuclear strong force Holds positive particles together

Composed of two particles Protons Neutrons

Protons mass = 1.673 x 10-27 kg 1826 times greater than e-

Nuclear strong force Holds positive particles together

Atomic NumberAtomic Number

Atoms of different elements have different number of protons

Atomic number (Z) number of protons in the nucleus

Elements arranged in order of their atomic number on periodic table

Atoms of different elements have different number of protons

Atomic number (Z) number of protons in the nucleus

Elements arranged in order of their atomic number on periodic table

Mass NumberMass Number

Total number of protons and neutrons

Ex. Hydrogen Isotopes

Total number of protons and neutrons

Ex. Hydrogen IsotopesAtomic # # of Neutrons Mass #

Protium 1 0 1Deuterium 1 1 2Tritium 1 2 3

IsotopesIsotopes

Element may contain different number of neutrons

Isotopes have differing mass Naming

Helium-4 (hyphen notation) 4

2Helium (nuclear symbol)

Element may contain different number of neutrons

Isotopes have differing mass Naming

Helium-4 (hyphen notation) 4

2Helium (nuclear symbol)

ProblemsProblems

How many protons, electrons, and neutrons are in an atom of carbon-13?

Write the nuclear symbol for oxygen-16.

How many protons, electrons, and neutrons are in an atom of bromine-80?

Write the nuclear symbol for carbon-13. Write the hyphen notation for the

element that contains 15 electrons and 15 neutrons.

How many protons, electrons, and neutrons are in an atom of carbon-13?

Write the nuclear symbol for oxygen-16.

How many protons, electrons, and neutrons are in an atom of bromine-80?

Write the nuclear symbol for carbon-13. Write the hyphen notation for the

element that contains 15 electrons and 15 neutrons.

Relative Atomic MassesRelative Atomic Masses

Atomic mass unit (amu) 1/12 the mass of carbon-12 1.660 540 x 10-27 kg

Hydrogen-1 = 1 amu Average atomic mass

Weighted average of atomic masses of isotopes

Atomic mass unit (amu) 1/12 the mass of carbon-12 1.660 540 x 10-27 kg

Hydrogen-1 = 1 amu Average atomic mass

Weighted average of atomic masses of isotopes

Average Atomic MassAverage Atomic Mass

Ex. 25% weigh 2.00 g 75% weigh 3.00 g (2.00 g x 0.25) + (3.00 g x 0.75) =

2.75 g

Ex. 25% weigh 2.00 g 75% weigh 3.00 g (2.00 g x 0.25) + (3.00 g x 0.75) =

2.75 g

ProblemProblem

What is the average atomic mass of copper which consists of 69.17% copper-63 (62.929 598 amu), and copper-65 (64.927 793 amu)?

What is the average atomic mass of copper which consists of 69.17% copper-63 (62.929 598 amu), and copper-65 (64.927 793 amu)?

ProblemsProblems

Three isotopes of argon occur in nature - Ar-36, Ar-38, Ar-40. Calculate the average atomic mass of argon to two decimal places, given the following relative atomic masses and abundances of each of the isotopes: argon-36 (35.97 amu; 0.337%), argon-38 (37.96 amu; 0.063%), and argon-40 (39.96 amu; 99.600%).

Three isotopes of argon occur in nature - Ar-36, Ar-38, Ar-40. Calculate the average atomic mass of argon to two decimal places, given the following relative atomic masses and abundances of each of the isotopes: argon-36 (35.97 amu; 0.337%), argon-38 (37.96 amu; 0.063%), and argon-40 (39.96 amu; 99.600%).

The MoleThe Mole

Amount of substance that contains as many particles as there are atoms in exactly 12 g of carbon-12

Counting unit like dozen Dozen = 12 Mole = 6.022 x 1023

Avogadro’s number 6.022 x 1023

Amount of substance that contains as many particles as there are atoms in exactly 12 g of carbon-12

Counting unit like dozen Dozen = 12 Mole = 6.022 x 1023

Avogadro’s number 6.022 x 1023

Molar MassMolar Mass

Mass of one mole of pure substance

Units → g/mol Molar mass = atomic mass in amu

Mass of one mole of pure substance

Units → g/mol Molar mass = atomic mass in amu

ConversionsConversions

ConversionsConversions

1 mol/(6.022 x 1023) atoms Molar mass/mol

1 mol/(6.022 x 1023) atoms Molar mass/mol

ProblemsProblems

What is the mass in grams of 3.6 mol of the element carbon, C?

What is the mass in grams of 0.733 mol of the element chlorine, Cl?

How many moles of copper, Cu, are in 3.22 g of copper?

How many moles of lithium, Li, are in 2.72 x 10-4 g of lithium?

What is the mass in grams of 3.6 mol of the element carbon, C?

What is the mass in grams of 0.733 mol of the element chlorine, Cl?

How many moles of copper, Cu, are in 3.22 g of copper?

How many moles of lithium, Li, are in 2.72 x 10-4 g of lithium?

ProblemsProblems

How many moles of carbon, C, are in 2.25 x 1022 atoms of carbon?

How many moles of oxygen, O are in 2 000 000 atoms of oxygen?

How many atoms of sodium, Na, are in 3.80 mol of sodium?

What is the mass in grams of 5.0 x 109 atoms of neon, Ne?

How many moles of carbon, C, are in 2.25 x 1022 atoms of carbon?

How many moles of oxygen, O are in 2 000 000 atoms of oxygen?

How many atoms of sodium, Na, are in 3.80 mol of sodium?

What is the mass in grams of 5.0 x 109 atoms of neon, Ne?

ProblemsProblems

How many atoms of carbon, C, are in 0.020 g of carbon?

What mass of silver, Ag, contains the same number of atoms as 10.0 g of boron, B?

How many moles of CO2 are in 66.0 g of dry ice, which is solid CO2

How many atoms of carbon, C, are in 0.020 g of carbon?

What mass of silver, Ag, contains the same number of atoms as 10.0 g of boron, B?

How many moles of CO2 are in 66.0 g of dry ice, which is solid CO2

Chapter ReviewChapter Review

Pg. 89 1, 8, 11, 17, 18acd, 20, 21, 22ade,

23abcd

Pg. 89 1, 8, 11, 17, 18acd, 20, 21, 22ade,

23abcd