Chemistry: Introduction to the Periodic Table - Dmitri Mendeleev

Summary

The periodic table is a chemist's essential tool for organizing and predicting chemical behaviors by element position. It features elements in squares with their chemical symbols, atomic numbers, and atomic masses. Metals typically reside on the left and center, while nonmetals are on the upper right, with metalloids in between. Elements are arranged by atomic number to reveal periodicity, forming groups with similar properties and periods corresponding to electron energy levels. The table has evolved, with Dmitri Mendeleev's predictive contributions and Henry Moseley's refinements, and continues to expand with new element discoveries.

Takeaways

• 📚 The periodic table is essential for organizing chemical information and predicting chemical behavior.
• 🔍 Each element on the periodic table is represented by a unique square with a one or two-letter chemical symbol, atomic number, and atomic mass.
• 🌐 Many chemical symbols originate from Latin, such as 'Ag' for silver and 'Pb' for lead.
• 📊 The table is divided into metals, nonmetals, and metalloids, with metals typically located on the left and middle, and nonmetals on the upper right.
• 🔋 Metallic elements are good conductors of heat and electricity, while nonmetals are not.
• 📈 The periodic table is arranged to show periodicity, where elements with similar properties repeat in a predictable pattern.
• 🏗️ Elements are organized into groups (families) and periods based on their electron configurations and energy levels.
• 🌀 The leftmost groups include alkali metals and alkali earth metals with s orbitals being filled, while the rightmost block contains noble gases with filled valence shells.
• 🔄 The periodic table has evolved over time with the IUPAC proposing a system that numbers groups 1-18 to eliminate confusion from different numbering systems.
• 🔮 Dmitri Mendeleev is credited with the development of the periodic table, which he organized by atomic mass and predicted the existence of undiscovered elements.
• 🌟 Henry Moseley's work led to a significant modification of the periodic table, organizing elements by atomic number rather than atomic mass, resolving inconsistencies and predicting new elements.

Q & A

What is the primary purpose of the periodic table in chemistry?

The primary purpose of the periodic table is to organize chemical information, which allows chemists to predict the chemical behavior of elements based on their position on the table.

How are chemical symbols related to the names of elements?

Many chemical symbols are derived from the English names of elements, but some originate from other languages, such as Latin, like 'Ag' for silver from 'argentum' and 'Pb' for lead from 'plumbum'.

What information is typically found on the periodic table above and below the chemical symbol?

Above the chemical symbol is the atomic number of the element, and below the symbol are the full name of the element and its atomic mass.

Where on the periodic table are metals typically found, and what are their general properties?

Metals are typically found on the left and in the middle of the periodic table. They are generally shiny and are good conductors of heat and electricity.

What is the difference between metals and nonmetals on the periodic table?

Nonmetals are found on the upper right of the periodic table and are generally not shiny and not good conductors of heat or electricity, unlike metals.

What are metalloids and where are they located on the periodic table?

Metalloids are elements found on either side of the thick staircase dividing line between metals and nonmetals on the periodic table. They have properties that fall between metals and nonmetals.

Why are elements organized into rows and columns on the periodic table instead of a simple list?

Elements are organized into rows and columns to reveal a pattern of periodicity, or repeating characteristics, which helps in predicting their chemical behavior.

What is the significance of the groups (vertical columns) in the periodic table?

A group or family in the periodic table consists of elements with similar chemical properties, which is due to their similar valence electron configurations.

How does the periodic law relate to the organization of elements into columns on the periodic table?

The periodic law, which describes the periodic repetition of certain characteristics among elements, is the basis for organizing elements into columns on the periodic table.

Who is credited with the development of the modern periodic table, and what was his significant contribution?

Dmitri Mendeleev is credited with the development of the modern periodic table. His significant contribution was listing the elements in order of increasing atomic mass and leaving gaps for undiscovered elements, which he predicted would exist.

What modification did Henry Moseley make to the periodic table, and how did it affect the organization of elements?

Henry Moseley modified the periodic table by organizing elements in increasing order of atomic number instead of atomic mass, which resolved some inconsistencies and is a more accurate predictor of chemical behavior.

Outlines

00:00

🔬 The Power and Structure of the Periodic Table

The periodic table is a crucial tool for organizing chemical information, allowing chemists to predict chemical behaviors based on an element's position. Each element is represented by a square with its chemical symbol, atomic number, full name, and atomic mass. Elements are categorized as metals, nonmetals, or metalloids, with metals typically located on the left and in the middle, nonmetals on the upper right, and metalloids in between. The table is organized into rows (periods) and columns (groups or families), reflecting the periodic law of repeating chemical properties. Elements within a group share similar properties due to similar valence electron configurations. The table has evolved over time, with the IUPAC proposing a standardized numbering system from 1 to 18 to avoid confusion across different systems.

05:04

📚 Historical Development and Refinements of the Periodic Table

The periodic table has undergone refinements since its inception, with early versions lacking many elements and a standardized classification system. Dmitri Mendeleev is credited with developing the modern periodic table by listing elements in order of increasing atomic mass and grouping them by similar properties, leaving gaps for undiscovered elements which he predicted. His system was later refined by Henry Moseley, who discovered a relationship between X-ray wavelengths and atomic numbers, leading to the reorganization of the table based on atomic numbers. Moseley also predicted the existence of new elements, which have since been discovered. The periodic table continues to evolve with the discovery of new elements, and its structure may need to be expanded in the future.

Keywords

💡Periodic Table

The Periodic Table is a tabular arrangement of chemical elements organized by atomic number, electron configurations, and recurring chemical properties. It is a fundamental tool in chemistry, allowing chemists to predict and understand the behavior of elements. In the video, the Periodic Table is described as invaluable for its predictive capabilities, with elements arranged in a way that reveals patterns and periodicity, which are key to understanding their chemical properties.

💡Chemical Symbol

A chemical symbol is a one or two-letter abbreviation used to represent an element in the Periodic Table. These symbols often derive from the element's name in various languages, such as Latin, as seen with 'Ag' for silver (argentum) and 'Pb' for lead (plumbum). The script emphasizes that each element has a unique square on the table with its symbol, which is crucial for identifying and distinguishing elements.

💡Atomic Number

The atomic number of an element, found above its chemical symbol on the Periodic Table, represents the number of protons in the nucleus of an atom. This number is unique to each element and determines its position on the table. The script explains that the elements are listed in order of increasing atomic number, which is essential for understanding the periodicity of properties.

💡Metals and Nonmetals

Metals and nonmetals are two broad categories of elements with distinct physical and chemical properties. Metals, typically found on the left and middle of the Periodic Table, are shiny and good conductors of heat and electricity. Nonmetals, found on the upper right (except for hydrogen), are generally not shiny and poor conductors. The script uses these categories to illustrate the physical properties of elements and their placement on the table.

💡Metalloids

Metalloids are elements that have properties intermediate between metals and nonmetals. They are found along a 'staircase' line on the Periodic Table that divides metals from nonmetals. The script mentions metalloids as a transitional category, highlighting their unique position and properties that blend characteristics of both metals and nonmetals.

💡Periodic Law

The Periodic Law states that the properties of elements repeat periodically with the increase in atomic number. This law is the foundation for the arrangement of elements into columns (groups or families) on the Periodic Table. The script explains that this periodic repetition, such as the appearance of inert gases and reactive elements, is what led to the organization of elements into groups with similar chemical properties.

💡Groups (Families)

Groups, or families, are the vertical columns of elements on the Periodic Table that share similar chemical properties due to having similar valence electron configurations. The script emphasizes that elements in a group are organized this way because they exhibit similar behaviors, which is a direct result of the Periodic Law.

💡Periods

Periods are the horizontal rows of elements on the Periodic Table, each corresponding to a different energy level occupied by electrons. The script mentions that there are seven periods, with the elements in each period having electrons filling progressively higher energy levels, which influences their chemical properties.

💡Alkali Metals and Alkaline Earth Metals

Alkali metals and alkaline earth metals are two groups of elements found on the far left of the Periodic Table. These elements have their outermost s orbitals being filled, which gives them similar chemical properties. The script uses these groups as examples of how the arrangement of elements by electron configuration leads to groups with shared characteristics.

💡Transition Metals

Transition metals are a block of elements in the middle of the Periodic Table, where the outermost d orbitals are being filled. The script describes these elements as having unique properties due to their electron configurations, and they are known for their ability to form a variety of compounds.

💡Inner Transition Metals

Inner transition metals, also known as the Lanthanides and Actinides, are two rows of elements at the bottom of the Periodic Table with their outermost f orbitals being filled. The script mentions these elements as an example of how the Periodic Table has been expanded to accommodate the discovery of new elements with unique electron configurations.

💡Dmitri Mendeleev

Dmitri Mendeleev was a Russian chemist who is credited with the development of the Periodic Table. The script highlights Mendeleev's contribution by organizing elements by atomic mass and predicting the existence and properties of elements that were yet to be discovered, which later proved the predictive power of the Periodic Table.

💡Henry Moseley

Henry Moseley was an English physicist who made significant modifications to the Periodic Table by suggesting that elements should be organized by atomic number rather than atomic mass. The script explains that Moseley's work resolved inconsistencies and further refined the table's predictive capabilities by linking the X-ray wavelengths of elements to their atomic numbers.

Highlights

The periodic table is essential for organizing chemical information and predicting chemical behavior.

Each element on the periodic table is represented by a unique chemical symbol.

Some chemical symbols originate from Latin, such as Ag for silver and Pb for lead.

The atomic number, representing the number of protons, is displayed above the chemical symbol.

Metallic elements are typically found on the left and in the middle of the periodic table.

Nonmetals are located on the upper right, with the exception of hydrogen.

Metalloids, with properties between metals and nonmetals, are found near the staircase dividing line.

Elements are listed in order of increasing atomic number, revealing a pattern of periodicity.

The periodic law describes the repeating characteristics of elements when arranged by atomic number.

Elements in a group (vertical column) have similar chemical properties due to similar valence electron configurations.

There are 7 horizontal rows called periods, each corresponding to a different energy level of electron occupation.

Alkali metals and alkali earth metals are on the far left, with s orbitals being filled.

The block of 6 columns on the right includes elements with p orbitals being filled, including noble gases.

Transition metals in the middle have d orbitals being filled, indicated by the asterisks at the bottom.

The periodic table has undergone various numbering systems for groups over the years.

IUPAC proposed a system numbering groups 1-18 to eliminate confusion among different numbering systems.

Dmitri Mendeleev is credited with the development of the periodic table, organizing elements by atomic mass.

Mendeleev's table included gaps for undiscovered elements, which were later found and matched his predictions.

Henry Moseley's work established atomic number as a more significant predictor of chemical behavior than atomic mass.

Moseley reorganized the periodic table by atomic number, resolving inconsistencies in Mendeleev's version.

There are 92 naturally occurring elements, and many synthesized elements, requiring potential enlargement of the periodic table.

Transcripts

The periodic table is the most powerful tool chemists have for organizing chemical information.

Without it, chemistry would be a chaotic, confusing jumble of seemingly random observations.

What makes the periodic table really invaluable is its use as a predictive tool. You can predict

a lot about the chemical behavior of an element if you know where it is on the periodic table.

Each element is represented by one square on the periodic table, with a one or two-letter

chemical symbol. Many of the chemical symbols are derived from the English name for the

element, but some come from other languages. For example, the symbol for silver is Ag,

from the Latin word argentum. The symbol for lead is Pb, from the Latin word plumbum.

Above the chemical symbol is the atomic number of the element, and below the symbol are the

full name of the element and its atomic mass.

Most elements are metals, and you can find them on the left and in the middle of the

periodic table. Metallic elements are typically shiny and are good conductors of heat and

electricity. Nonmetals are found on the upper right of the periodic table (except for Hydrogen

there on the left, it’s also a nonmetal). Nonmetals generally are NOT shiny and are

NOT good conductors of heat or electricity. The dividing line between metals and nonmetals

on the periodic table is drawn as a thick staircase. The elements that are found on

either side of that staircase are often called METALLOIDS, and they have properties that

fall between metals and nonmetals.

Notice that the atoms are listed in order of increasing atomic number, as you read the

periodic table from left to right, top to bottom. Each element has a unique atomic number

- that’s the number of protons in the nucleus of the atom. So why are the elements organized

into rows and columns? Why don’t we just put the elements in a long list?

It turns out, if you arrange elements by atomic number, a pattern emerges. There is a periodicity,

or a repeating, of certain characteristics. For example, every so often, an inert gas

appears. Right next to it will be an element that reacts violently with water. This periodic

repetition is known as the PERIODIC LAW. This is the basis for organizing the elements in

the Periodic Table into columns.

A vertical column of elements is called a GROUP or a FAMILY. The elements in a group

have similar chemical properties. We now know that’s because they have similar valence

electron configurations.

There are 7 horizontal rows in the periodic table. These rows are called PERIODS. Each

row corresponds to a different energy level occupied by electrons.

The two groups on the left are the alkali metals and the alkali earth metals. The s

orbitals in the outermost shell of the atom are being filled in these groups.

On the right is a block of 6 columns. These elements have the outermost p orbitals being

filled. Notice on the far right are the Noble gases, which all have a filled valence shell

of electrons.

In the middle is a block of 10 columns, the transition metals. In these elements, the

outermost d orbitals are being filled.

The asterisks take you to the bottom of the Periodic Table, where there are two rows of

14 columns, the inner transition metals - also known as the Lanthanides and Actinides. These

elements have the outermost f orbitals being filled.

The groups in the periodic table have been numbered in a variety of ways over the

years. Depending on which periodic table you look at, it may have 1, 2, or even 3 different

systems for numbering the groups. You may see the groups labeled with Roman

numerals and As and Bs - this system was popular in North America and Europe. Unfortunately,

the designations were somewhat arbitrary - in North America, the A groups were the s and

p blocks, known as the “Representative Elements,” and the B groups were the d block, the “Transition

Metals.” Meanwhile, in Europe, the A groups were on the left, and the B groups were on

the right. In both systems, there was one triple-sized group called Roman numeral VIII.

To eliminate all this confusion, the International Union of Pure and Applied Chemistry (IUPAC)

proposed a system that numbers the groups 1-18, with no As or Bs.

This is an example of the sorts of refinements that have changed the Periodic Table gradually

over the years, as new discoveries were made and chemists came to agreements about how

to present the new information. You may not even recognize the first periodic table - fewer

than 70 elements had been discovered in the mid 1800s - they didn’t know about noble

gases yet. At that point, there was no agreed upon way to list the elements that was of

any help to chemists. For example, listing them in the order of discovery didn’t tell

you anything about their chemical behavior, so that kind of list would be useless as any

kind of predictive tool. This was the state of affairs when Russian chemist Dmitri Mendeleev

developed the Periodic Table.

In 1869, Mendeleev came up with the idea of listing the elements in order of increasing

ATOMIC MASS. Almost simultaneously, Lothar Meyer in Germany published a nearly identical

system for classifying elements. We generally give credit for the discovery to Mendeleev,

because he devoted so much time and effort championing this new system and he helped

it become widely accepted.

Mendeleev insisted that elements with similar properties be listed together, and because

of this, there were gaps in his table. Mendeleev boldly proposed the existence of a number

of elements that had not yet been found, that would one day fill in these gaps. He named

them for their positions in his table. For example, the proposed element eka-aluminum

would reside under aluminum, and eka-silica would go under silicon. Some years later,

these elements were indeed found, and their characteristics closely matched Mendeleev’s

predictions. This was a powerful example of the utility of Mendeleev’s periodic table

as a PREDICTIVE tool, something that chemists didn’t have before.

In 1913, English physicist Henry Moseley made an important modification to the Periodic

Table. Moseley, a member of Ernest Rutherford’s research group, was probing metallic elements

with X-rays and measuring the wavelength of the X-ray emissions. He found that each element

gave different results. Moseley developed a mathematical relationship between the X

ray wavelengths produced by different elements and their atomic number, which increased by

1 for each element. Moseley suggested that the atomic number was more significant for

predicting chemical behavior than the atomic mass as had been previously thought.

Moseley reorganized the elements in the periodic table, listing them in increasing order of

atomic number instead of atomic mass. This resolved some inconsistencies with Mendeleev’s

table. For instance, Argon has a greater atomic mass than Potassium, but a lower atomic number.

Like Mendeleev, Moseley left gaps in the Periodic Table where he proposed several yet-undiscovered

elements should fit. These included atomic numbers 43, 61, 72, and 75.

Moseley’s proposed elements and many more have since been discovered. There are 92 naturally

occurring elements, and many elements not found in nature have been synthesized. We’re

running out of room to put the all the new elements! We just might have to enlarge the

Periodic Table in the near future.