Chemistry Unit 2 PPT

UNIT 2:Finding Patterns

Chemistry

Physics and the Quantum Mechanical Model

Neon advertising signs are formed from glass tubes bent in various shapes. An electric current passing through the gas in each glass tube makes the gas glow with its own characteristic color. You will learn why each gas glows with a specific color of light.

5.3

Light

LightHow are the wavelength and frequency of light related?

5.3

Light

The amplitude of a wave is the wave’s height from zero to the crest.

The wavelength, represented by (the Greek letter lambda), is the distance between the crests.

5.3

Light

The frequency, represented by (the Greek letter nu), is the number of wave cycles to pass a given point per unit of time.

The SI unit of cycles per second is called a hertz (Hz).

5.3

LightThe wavelength and frequency of light are inversely proportional to each other.

5.3

Light

The product of the frequency and wavelength always equals a constant (c), the speed of light.

5.3

Light

According to the wave model, light consists of electromagnetic waves.Electromagnetic radiation

includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays.

All electromagnetic waves travel in a vacuum at a speed of 2.998 108 m/s.

5.3

Light

Sunlight consists of light with a continuous range of wavelengths and frequencies. When sunlight passes

through a prism, the different frequencies separate into a spectrum of colors.

In the visible spectrum, red light has the longest wavelength and the lowest frequency.

5.3

The electromagnetic spectrum consists of radiation over a broad band of wavelengths.

5.3

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Atomic Spectra

Atomic SpectraWhat causes atomic emission spectra?

5.3

Atomic Spectra

When atoms absorb energy, electrons move into higher energy levels. These electrons then lose energy by emitting light when they return to lower energy levels.

5.3

A prism separates light into the colors it contains. When white light passes through a prism, it produces a rainbow of colors.

5.3

When light from a helium lamp passes through a prism, discrete lines are produced.

5.3

The frequencies of light emitted by an element separate into discrete lines to give the atomic emission spectrum of the element.

5.3

Mercury Nitrogen

An Explanation of Atomic Spectra

An Explanation of Atomic SpectraHow are the frequencies of light an atom emits related to changes of electron energies?

5.3

An Explanation of Atomic Spectra In the Bohr model, the lone electron in

the hydrogen atom can have only certain specific energies.When the electron has its lowest

possible energy, the atom is in its ground state.

Excitation of the electron by absorbing energy raises the atom from the ground state to an excited state.

A quantum of energy in the form of light is emitted when the electron drops back to a lower energy level.

5.3

An Explanation of Atomic Spectra

The light emitted by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron.

5.3

The three groups of lines in the hydrogen spectrum correspond to the transition of electrons from higher energy levels to lower energy levels.

5.3

Quantum Mechanics

Quantum MechanicsHow does quantum mechanics differ from classical mechanics?

5.3

Quantum Mechanics

In 1905, Albert Einstein successfully explained experimental data by proposing that light could be described as quanta of energy.The quanta behave as if they

were particles.Light quanta are called photons.

In 1924, De Broglie developed an equation that predicts that all moving objects have wavelike behavior.

5.3

Quantum Mechanics Today, the wavelike properties of beams of electrons

are useful in magnifying objects. The electrons in an electron microscope have much smaller wavelengths than visible light. This allows a much clearer enlarged image of a very small object, such as this mite.

5.3

Quantum Mechanics

Classical mechanics adequately describes the motions of bodies much larger than atoms, while quantum mechanics describes the motions of subatomic particles and atoms as waves.

5.3

Quantum Mechanics

The Heisenberg uncertainty principle states that it is impossible to know exactly both the velocity and the position of a particle at the same time.This limitation is critical in dealing

with small particles such as electrons.

This limitation does not matter for ordinary-sized object such as cars or airplanes.

5.3

Quantum Mechanics

The Heisenberg Uncertainty Principle

5.3

Models of the Atom

The scale model shown is a physical model. However, not all models are physical. In fact, several theoretical models of the atom have been developed over the last few hundred years. You will learn about the currently accepted model of how electrons behave in atoms.

5.1

The Development of Atomic Models

The Development of Atomic ModelsWhat was inadequate about Rutherford’s atomic model?

5.1


Rutherford’s atomic model could not explain the chemical properties of elements. Rutherford’s atomic model could not

explain why objects change color when heated.

5.1


The timeline shoes the development of atomic models from 1803 to 1911.

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The timeline shows the development of atomic models from 1913 to 1932.

5.1

The Bohr Model

The Bohr ModelWhat was the new proposal in the Bohr model of the atom?

5.1

The Bohr Model

Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus.

5.1

The Bohr Model

Each possible electron orbit in Bohr’s model has a fixed energy.The fixed energies an electron

can have are called energy levels.

A quantum of energy is the amount of energy required to move an electron from one energy level to another energy level.

5.1

Like the rungs of the strange ladder, the energy levels in an atom are not equally spaced.

The higher the energy level occupied by an electron, the less energy it takes to move from that energy level to the next higher energy level.

5.1

The Quantum Mechanical Model

The Quantum Mechanical ModelWhat does the quantum mechanical model determine about the electrons in an atom?

5.1


The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus.

5.1


Austrian physicist Erwin Schrödinger (1887–1961) used new theoretical calculations and results to devise and solve a mathematical equation describing the behavior of the electron in a hydrogen atom.

The modern description of the electrons in atoms, the quantum mechanical model, comes from the mathematical solutions to the Schrödinger equation.

5.1


The propeller blade has the same probability of being anywhere in the blurry region, but you cannot tell its location at any instant. The electron cloud of an atom can be compared to a spinning airplane propeller.

5.1


In the quantum mechanical model, the probability of finding an electron within a certain volume of space surrounding the nucleus can be represented as a fuzzy cloud. The cloud is more dense where the probability of finding the electron is high.

5.1

Atomic Orbitals

Atomic OrbitalsHow do sublevels of principal energy levels differ?

5.1

Atomic Orbitals

An atomic orbital is often thought of as a region of space in which there is a high probability of finding an electron.Each energy sublevel

corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

5.1

Atomic Orbitals

Different atomic orbitals are denoted by letters. The s orbitals are spherical, and p orbitals are dumbbell-shaped.

5.1

Atomic Orbitals

Four of the five d orbitals have the same shape but different orientations in space.

5.1

The numbers and kinds of atomic orbitals depend on the energy sublevel.

5.1

Atomic Orbitals

The number of electrons allowed in each of the first four energy levels are shown here.

5.1

Electron Arrangement in Atoms

If this rock were to tumble over, it would end up at a lower height. It would have less energy than before, but its position would be more stable. You will learn that energy and stability play an important role in determining how electrons are configured in an atom.

5.2

Electron Configurations

Electron ConfigurationsWhat are the three rules for writing the electron configurations of elements?

5.2


The ways in which electrons are arranged in various orbitals around the nuclei of atoms are called electron configurations.Three rules—the aufbau

principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms.

5.2

Aufbau PrincipleAccording to the aufbau principle, electrons

occupy the orbitals of lowest energy first. In the aufbau diagram below, each box represents an atomic orbital.

5.2


Pauli Exclusion PrincipleAccording to the Pauli exclusion principle, an atomic orbital may describe at most two electrons. To occupy the same orbital, two electrons must have opposite spins; that is, the electron spins must be paired.

5.2


Hund’s RuleHund’s rule states that electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible.

5.2


Orbital Filling Diagram5.2

for Conceptual Problem 1.1

Exceptional Electron Configurations

Exceptional Electron ConfigurationsWhy do actual electron configurations for some elements differ from those assigned using the aufbau principle?

5.2

Exceptional Electron Configurations

Some actual electron configurations differ from those assigned using the aufbau principle because half-filled sublevels are not as stable as filled sublevels, but they are more stable than other configurations.

5.2

Exceptional Electron ConfigurationsExceptions to the

aufbau principle are due to subtle electron-electron interactions in orbitals with very similar energies.

Copper has an electron configuration that is an exception to the aufbau principle.

5.2

Organizing the Elements

6.1

6.1

Organizing the Elements In a self-service store,

the products are grouped according to similar characteristics. With a logical classification system, finding and comparing products is easy. You will learn how elements are arranged in the periodic table and what that arrangement reveals about the elements.

Searching For an Organizing Principle

Searching For an Organizing PrincipleHow did chemists begin to organize the known elements?

6.1


Chemists used the properties of elements to sort them into groups.

6.1


Chlorine, bromine, and iodine have very similar chemical properties.

6.1

Mendeleev’s Periodic Table

Mendeleev’s Periodic TableHow did Mendeleev organize his periodic table?

6.1


Mendeleev arranged the elements in his periodic table in order of increasing atomic mass.

The periodic table can be used to predict the properties of undiscovered elements.

6.1


An Early Version of Mendeleev’s Periodic Table

6.1

The Periodic Law

The Periodic LawHow is the modern periodic table organized?

6.1

The Periodic Law

In the modern periodic table, elements are arranged in order of increasing atomic number.

6.1

The Periodic Law

The periodic law: When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.The properties of the elements

within a period change as you move across a period from left to right.

The pattern of properties within a period repeats as you move from one period to the next.

6.1

Metals, Nonmetals, and Metalloids

Metals, Nonmetals, and MetalloidsWhat are three broad classes of elements?

6.1


Three classes of elements are metals, nonmetals, and metalloids.

Across a period, the properties of elements become less metallic and more nonmetallic.

6.1


Metals, Metalloids, and Nonmetals in the Periodic Table

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MetalsMetals are good conductors of heat and electric current.80% of elements are metals.

Metals have a high luster, are ductile, and are malleable.

6.1


Uses of Iron, Copper, and Aluminum

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NonmetalsIn general, nonmetals are

poor conductors of heat and electric current.Most nonmetals are gases

at room temperature.A few nonmetals are solids,

such as sulfur and phosphorus.

One nonmetal, bromine, is a dark-red liquid.

6.1


MetalloidsA metalloid generally has properties that are similar to those of metals and nonmetals.

The behavior of a metalloid can be controlled by changing conditions.

6.1


If a small amount of boron is mixed with silicon, the mixture is a good conductor of electric current. Silicon can be cut into wafers, and used to make computer chips.

6.1

Classifying the Elements

6.2

6.2

Classifying the Elements A coin may contain much

information in a small space—its value, the year it was minted, and its country of origin. Each square in a periodic table also contains information. You will learn what types of information are usually listed in a periodic table.

6.2

Squares in the Periodic Table

Squares in the Periodic TableWhat type of information can be displayed in a periodic table?


The periodic table displays the symbols and names of the elements, along with information about the structure of their atoms.

6.2


The background colors in the squares are used to distinguish groups of elements.The Group 1A elements are

called alkali metals.The Group 2A elements are

called alkaline earth metals.

The nonmetals of Group 7A are called halogens.

6.2

6.2

Electron Configurations in Groups

Electron Configurations in GroupsHow can elements be classified based on their electron configurations?

6.2


Elements can be sorted into noble gases, representative elements, transition metals, or inner transition metals based on their electron configurations.

6.2


The blimp contains helium, one of the noble gases.

6.2


The Noble GasesThe noble gases are the

elements in Group 8A of the periodic table. The electron configurations for the first four noble gases in Group 8A are listed below.

6.2


The Representative ElementsElements in groups 1A through 7A are

often referred to as representative elements because they display a wide range of physical and chemical properties. The s and p sublevels of the highest

occupied energy level are not filled.The group number equals the number

of electrons in the highest occupied energy level.

6.2


In atoms of the Group 1A elements below, there is only one electron in the highest occupied energy level.

6.2


In atoms of the Group 4A elements below, there are four electrons in the highest occupied energy level.

6.2

Representative Elements


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6.2

Transition Elements

Transition ElementsThere are two types of transition elements—transition metals and inner transition metals. They are classified based on their electron configurations.

6.2

Transition ElementsIn atoms of a transition metal, the highest occupied s sublevel and a nearby d sublevel contain electrons.

In atoms of an inner transition metal, the highest occupied s sublevel and a nearby f sublevel generally contain electrons.

6.2

Transition Elements

Blocks of Elements

6.2

Periodic Trends 6.3

Periodic Trends

Sodium chloride (table salt) produced the geometric pattern in the photograph. Such a pattern can be used to calculate the position of nuclei in a solid. You will learn how properties such as atomic size are related to the location of elements in the periodic table.

6.3

Trends in Atomic Size

Trends in Atomic SizeWhat are the trends among the elements for atomic size?

6.3


The atomic radius is one half of the distance between the nuclei of two atoms of the same element when the atoms are joined.

6.3


Group and Periodic Trends in Atomic SizeIn general, atomic size increases from top to bottom within a group and decreases from left to right across a period.

6.3


6.3

6.3

Ions

IonsHow do ions form?

6.3

Ions

Positive and negative ions form when electrons are transferred between atoms.

6.3

Ions

Positive and negative ions form when electrons are transferred between atoms.

6.3

Ions

Some compounds are composed of particles called ions.An ion is an atom or group of

atoms that has a positive or negative charge.

A cation is an ion with a positive charge.

An anion is an ion with a negative charge.

6.3

Trends in Ionization Energy

Trends in Ionization EnergyWhat are the trends among the elements for first ionization energy, ionic size, and electronegativity?

6.3


The energy required to remove an electron from an atom is called ionization energy.The energy required to

remove the first electron from an atom is called the first ionization energy.

The energy required to remove an electron from an ion with a 1+ charge is called the second ionization energy.

6.3


Group and Periodic Trends in Ionization EnergyFirst ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.

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Trends in Ionic Size

Trends in Ionic SizeDuring reactions between metals and nonmetals, metal atoms tend to lose electrons, and nonmetal atoms tend to gain electrons. The transfer has a predictable effect on the size of the ions that form.

6.3


Cations are always smaller than the atoms from which they form. Anions are always larger than the atoms from which they form.

6.3


Relative Sizes of Some Atoms and Ions

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Trends in Electronegativity

Trends in ElectronegativityElectronegativity is the ability

of an atom of an element to attract electrons when the atom is in a compound.In general, electronegativity

values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.

6.3

Trends in Electronegativity

Representative Elements in Groups 1A through 7A

6.3

Summary of Trends

Summary of TrendsWhat is the underlying cause of periodic trends?

6.3

Summary of Trends

The trends that exist among these properties can be explained by variations in atomic structure.

6.3

Chemistry 7.1

IonsPyrite (FeS2), a common

mineral that emits sparks when struck against steel, is often mistaken for gold—hence its nickname, “fool’s gold.” Pyrite is an example of a crystalline solid. In this chapter, you will learn about crystalline solids composed of ions that are bonded together. But first you need to understand how ions form from neutral atoms.

7.1

Valence Electrons

Valence ElectronsHow do you find the number of valence electrons in an atom of a representative element?

7.1

Valence Electrons

Valence electrons are the electrons in the highest occupied energy level of an element’s atoms.

The number of valence electrons largely determines the chemical properties of an element.

7.1

Valence Electrons

To find the number of valence electrons in an atom of a representative element, simply look at its group number.

7.1

Valence Electrons Applications of Group 4A

Elements

7.1

Carbon Silicon Germanium

Valence Electrons

Electron dot structures are diagrams that show valence electrons as dots.

7.1

The Octet Rule

The Octet RuleAtoms of which elements tend to gain electrons? Atoms of which elements tend to lose electrons?

7.1

The Octet Rule

Noble gases, such as neon and argon, are unreactive in chemical reactions. In 1916, chemist Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules.

He called his explanation the octet rule: In forming compounds, atoms tend to achieve the electron configuration of a noble gas.

7.1

The Octet Rule

Atoms of metals tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some non-metals tend to gain electrons or to share electrons with another nonmetal to achieve a complete octet.

7.1

Formation of Cations

Formation of CationsHow are cations formed?

7.1


An atom’s loss of valence electrons produces a cation, or a positively charged ion.

7.1


The most common cations are those produced by the loss of valence electrons from metal atoms.

You can represent the electron loss, or ionization, of the sodium atom by drawing the complete electron configuration of the atom and of the ion formed.

7.1

Formation of Cations The electron configuration of the

sodium ion is the same as that of a neon atom.

7.1


Using electron dot structures, you can show the ionization more simply.

7.1


The sodium atoms in a sodium-vapor lamp ionize to form sodium cations.

7.1

Formation of CationsA magnesium atom attains the electron configuration of neon by losing both valence electrons. The loss of valence electrons produces a magnesium cation with a charge of 2+.

7.1


Walnuts are a good dietary source of magnesium. Magnesium ions (Mg2+) aid in digestive processes.

7.1


Cations of Group 1A elements always have a charge of 1+. Cations of group 2A elements always have a charge of 2+.

7.1

Formation of Cations A copper atom can ionize to form a 1+ cation (Cu+). By losing its lone 4s electron, copper attains a pseudo noble-gas electron configuration.

7.1

Formation of Anions

Formation of AnionsHow are anions formed?

7.1

Formation of Anions

The gain of negatively charged electrons by a neutral atom produces an anion.An anion is an atom or a group

of atoms with a negative charge.

The name of an anion typically ends in -ide.

7.1

Formation of Anions

The figure shows the symbols of anions formed by some elements in Groups 5A, 6A, and 7A.

7.1

Formation of Anions A gain of one electron gives chlorine an octet and

converts a chlorine atom into a chloride ion. It has the same electron configuration as the noble gas argon.

7.1

Formation of AnionsBoth a chloride ion and the argon atom have

an octet of electrons in their highest occupied energy levels.

7.1

Formation of Anions

In this equation, each dot in the electron dot structure represents an electron in the valence shell in the electron configuration diagram.

7.1

Formation of Anions

The negatively charged ions in seawater—the anions—are mostly chloride ions.

7.1

Formation of Anions

The ions that are produced when atoms of chlorine and other halogens gain electrons are called halide ions.All halogen atoms have seven

valence electrons.All halogen atoms need to gain

only one electron to achieve the electron configuration of a noble gas.

7.1

Formation of Anions

Oxygen is in Group 6A.7.1

Formation of Anions

7.1

Conceptual Problem 7.1

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Practice Problems For Conceptual Problem 7.1

for Conceptual Problem 7.1

Chemistry Unit 2 PPT

Education

light light

frequency of light

frequencies of light

visible light

light quanta

speed of light

light sunlight

red light