Chem chapt 6

The Periodic Table and Periodic Law

Chemistry Chapter 6

Main IdeasMain Ideas Periodic trends in the properties of atoms allow us

to predict physical and chemical properties.

The periodic table evolved over time as scientists discovered more useful ways to compare and organize elements.

Elements are organized into different blocks in the periodic table according to their electron configurations.

Trends among elements in the periodic table include their size and their ability to lose or attract electrons

Development of the Development of the Modern Periodic TableModern Periodic Table

Objectives:

Trace the development of the periodic table

Identify key features of the periodic table

Development of the Development of the Periodic TablePeriodic Table

In the 1700’s, Lavoisier compiled a list of all the known elements of the time. 33 elements

The 1800s brought large amounts of information and scientists needed a way to organize knowledge about elements.

Advent of electricity – break down compounds

Development of the spectrometer – identify newly isolated elements

Industrial revolution – new chemistry based ingredients and compounds.

70 known elements by 1870

John Newlands proposed an arrangement where elements were ordered by increasing atomic mass.

Law of OctavesLaw of Octaves

Newlands (1864) noticed when the elements were arranged by increasing atomic mass, their properties repeated every eighth element.

Law of OctavesLaw of Octaves

Octaves was used due to the musical analogy, but was widely dismissed.

Some elements didn’t follow the pattern

The Periodic TableThe Periodic Table

Meyer and Mendeleev both demonstrated a connection between atomic mass and elemental properties.

Mendeleev’s Table – A Russian scientist – gets the most credit because he published first. Arranged elements by increasing mass

and columns with similar properties. Predicted the existence and properties

of undiscovered elements. Still some inconsistencies.

Moseley discovered that each element had a distinct number of protons. Once rearranged by increasing

atomic number, the table resulted in a clear periodic pattern.

Periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number is called periodic law.

The Modern Periodic The Modern Periodic TableTable

The modern periodic table contains boxes which contain the element's name, symbol, atomic number, and atomic mass.

Rows of elements are called periods. (total of 7)

Columns of elements are called groups. (total of 18)

Elements in groups 1,2, and 13-18 possess a wide variety of chemical and physical properties and are called the representative elements.

Elements in groups 3-12 are known as the transition elements .

Types of ElementsTypes of ElementsElements are classified as metals, non-metals, and

metalloids.

Metals are made up of most of the representative elements and all of the transition elements. They are generally shiny when smooth and clean, solid

at room temperature, and good conductors of heat and electricity.

Most are Ductile and Malleable – Ductile – the ability to be drawn into wire. Malleable – the ability to be pounded into sheets

Types of ElementsTypes of ElementsElements are classified as metals,

non-metals, and metalloids.

Alkali metals are all the elements in group 1 except hydrogen, and are very reactive.

Alkaline earth metals are in group 2, and are also highly reactive.

Types of ElementsTypes of Elements

The transition elements (groups 3 - 12) are divided into transition metals and inner transition metals. The two sets of inner transition metals are

called the lanthanide series and actinide series and are located at the bottom of the periodic table.

Lanthanides are phosphors – elements that emit light when struck by electrons.

Non-metals are elements that are generally gases or brittle, dull-looking solids, and poor conductors of heat and electricity.

Group 17 is composed of highly reactive elements called halogens.

Group 18 gases are extremely unreactive and commonly called noble gases.

Metalloids have physical and chemical properties of both metals and non-metals, such as silicon and germanium. They are found along the stair step of the table starting with Boron

QuestionsQuestions

What is a row of elements on the periodic table called? A. octave B. period C. group D. transition

QuestionsQuestions

What is silicon an example of? A. metal B. non-metal C. inner transition metal D. metalloid

Practice ProblemsPractice Problems Page 181 #1-7

Classification of the Classification of the ElementsElements

Objectives:

Explain why elements in the same group have similar properties.

Identify the four blocks of the periodic table on their electron configuration.

Organizing the Organizing the Elements by Electron Elements by Electron

ConfigurationConfiguration

Electron configuration determines the chemical properties of an element.

Recall electrons in the highest principal energy level are called valence electrons.

All group 1 elements have one valence electron.

All group 2 elements have two valence electrons.

ConfigurationConfiguration The energy level of an element’s valence

electrons indicates the period on the periodic table in which it is found.

The number of valence electrons for elements in groups 13-18 is ten less than their group number.

After the s-orbital is filled, valence electrons occupy the p-orbital.

Groups 13-18 contain elements with completely or partially filled p orbitals.

The d-block contains the transition metals and is the largest block. There are exceptions, but d-block elements

usually have filled outermost s orbital, and filled or partially filled d orbital.

The five d orbitals can hold 10 electrons, so the d-block spans ten groups on the periodic table.

The f-block contains the inner transition metals. f-block elements have filled or partially filled

outermost s orbitals and filled or partially filled 4f and 5f orbitals.

The 7 f orbitals hold 14 electrons, and the inner transition metals span 14 groups.

Practice ProblemsPractice Problems

Periodic TrendsPeriodic Trends

Objectives:

Compare period and group trends of several properties.

Relate period and group trends in atomic radii to electron configuration

Atomic RadiusAtomic RadiusAtomic radius – is determined by the amount of

positive charge in the nucleus and the number of valence electrons of an atom. It is usually measured in picometers (10-12).

For metals, atomic radius is half the distance between adjacent nuclei in a crystal of the element.

For nonmetals, the atomic radius is the distance between nuclei of identical atoms.

Atomic RadiusAtomic Radius

The periodic trend: decreases from left to right (periods) and increases top to bottom (groups) due to the increasing positive charge in the nucleus.

Atomic RadiusAtomic Radius

Atomic RadiusAtomic Radius Atomic radius generally increases as you

move down a group.

The outermost orbital size increases down a group, making the atom larger.

Valence electrons are not shielded from the increasing nuclear charge because no additional electrons come between the nucleus and the valence electrons.

Ionic RadiusIonic RadiusIons – atom(s) that gain or lose one or more electrons

to form a net charge.

Ionic radius is the radius of a charged atom.

When atoms lose electrons and form positively charged ions, they always become smaller. Lost electrons are usually valence electrons and

could leave the outer orbital empty and therefore smaller.

Electrostatic repulsion between remaining electrons decreases and pulls closer to nucleus.

Ionic RadiusIonic Radius

When atoms gain electrons and forms a negatively charged ion, they become larger. Increased electrostatic repulsion

increases distance of outer electrons.

Ionic RadiusIonic RadiusPeriodic Trend: radius of an ion

decreases from left to right (periods) until charge changes and then the radii increases dramatically. After the change, the radius continues to decrease. Ionic radii increases top to bottom (groups) until change in charge.

Ionic RadiusIonic Radius

Ionization EnergyIonization EnergyIonization energy is the energy needed to

remove an electron from the positive charge of the nucleus of a gaseous atom. (how strongly a nucleus holds on to an electron.)

First ionization energy is the energy required to remove the first electron.

Removing the second electron requires more energy, and is called the second ionization energy.

Ionization EnergyIonization Energy Atoms with large ionization energies

have a strong hold of its electrons and are less likely to form positive ions.

Atoms with low ionization energies lose their outer electrons easily and readily form positive ions.

The ionization at which the large increase in energy occurs is related to the number of valence electrons.

Ionization EnergyIonization EnergyPeriodic Trend: First ionization energy

increases from left to right across a period. First ionization energy decreases down a group because atomic size increases and less energy is required to remove an electron farther from the nucleus.

Ionization EnergyIonization Energy

The octet rule states that atoms tend to gain, lose or share electrons in order to acquire a full set of eight valence electrons. The octet rule is useful for predicting what types of ions an element is likely to form.

Ionization EnergyIonization Energy

ElectronegativityElectronegativityElectronegativity of an element

indicates its relative ability to attract electrons in a chemical bond. Measured in Paulings: numbers 4 and less.

ElectronegativityElectronegativityPeriodic Trend: electronegativity decreases

down a group and increases left to right across a period.

QuestionsQuestions

The lowest ionization energy is the ____. A. first B. second C. third D. fourth

QuestionsQuestions

The ionic radius of a negative ion becomes larger when: A. moving up a group B. moving right to left across period C. moving down a group D. the ion loses electrons

Practice ProblemsPractice Problems Page 189 #16-19; Page 194 #20-23

Key ConceptsKey Concepts The elements were first organized by increasing

atomic mass, which led to inconsistencies. Later, they were organized by increasing atomic number.

The periodic law states that when the elements are arranged by increasing atomic number, there is a periodic repetition of their chemical and physical properties.

The periodic table organizes the elements into periods (rows) and groups (columns); elements with similar properties are in the same group.

Key ConceptsKey Concepts Elements are classified as either metals, nonmetals,

or metalloids.

The periodic table has four blocks (s, p, d, f). Elements within a group have similar chemical

properties. The group number for elements in groups 1 and 2

equals the element’s number of valence electrons. The energy level of an atom’s valence electrons

equals its period number.

Key ConceptsKey Concepts Atomic and ionic radii decrease from left to right across a

period, and increase as you move down a group.

Ionization energies generally increase from left to right across a period, and decrease as you move down a group.

The octet rule states that atoms gain, lose, or share electrons to acquire a full set of eight valence electrons.

Electronegativity generally increases from left to right across a period, and decreases as you move down a group.

Chapter QuestionsChapter Questions

The actinide series is part of the

A. s-block elements.

B. inner transition metals.

C. non-metals.

D. alkali metals.

In their elemental state, which group has a complete octet of valence electrons?

A. alkali metals

B. alkaline earth metals

C. halogens

D. noble gases

Which block contains the transition metals?

A. s-block

B. p-block

C. d-block

D. f-block

An element with a full octet has how many valence electrons?

A. two

B. six

C. eight

D. ten

How many groups of elements are there?

Which group of elements are the least reactive?

A. alkali metals

B. inner transition metals

C. halogens

D. noble gases

On the modern periodic table, alkaline earth metals are found only in ____.

A. group 1

B. s-block

C. p-block

D. groups 13–18

Bromine is a member of the A. noble gases. B. inner transition metals. C. earth metals. D. halogens.

How many groups does the d-block span?

A. two

B. six

C. ten

D. fourteen

THE END

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