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Modern Periodic Table Quiz

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Questions and Answers

What is the basis of the tabular arrangement of all the chemical elements in the periodic table.

Atomic number

What does the modern periodic law, put forward by Henry Moseley, state?

The properties of elements are periodic functions of their atomic numbers

What does the number on the very top of each element's block in the periodic table represent?

Number of protons

Why are the elements arranged in vertical groups in the periodic table?

<p>Based on their similar properties</p> Signup and view all the answers

What does the number in the bottom of each element's block in the periodic table represent?

<p>Atomic mass number</p> Signup and view all the answers

What are the horizontal rows called in the periodic table?

<p>Periods</p> Signup and view all the answers

Which group of elements is known for their variable oxidation states, ability to form colored compounds, and often serving as catalysts in chemical reactions?

<p>Transition metals</p> Signup and view all the answers

Which element is used in medical implants and devices due to its biocompatibility and resistance to corrosion?

<p>Titanium</p> Signup and view all the answers

Which group of elements is found in Group 1 of the periodic table and is known for its high reactivity, low ionization energies, and good conductors of heat and electricity?

<p>Alkali metals</p> Signup and view all the answers

What is the most common flame test color for sodium?

<p>Yellow</p> Signup and view all the answers

Which element is crucial in the formation of hemoglobin in the human body?

<p>Iron</p> Signup and view all the answers

What are the general properties of alkali metals?

<p>Low melting and boiling points, high reactivity, and large atomic size</p> Signup and view all the answers

Which group of elements has larger atomic sizes compared to alkali metals but is less reactive than alkali metals?

<p>Alkaline earth metals</p> Signup and view all the answers

Which of the following elements is found in Group 2 of the periodic table and is known for its metallic nature, high melting and boiling points, and higher density?

<p>Magnesium</p> Signup and view all the answers

Which group of elements is known for being stored under oil or inert gases due to their vigorous reactivity with air and moisture?

Which group of elements has the unique characteristic of being in-between metals and nonmetals.

<p>Metalloids</p> Signup and view all the answers

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The periodic table is a tabular array of the chemical elements organized by atomic number , from the element with the lowest atomic number, hydrogen , to the element with the highest atomic number, oganesson . The atomic number of an element is the number of protons in the nucleus of an atom of that element. Hydrogen has 1 proton, and oganesson has 118.

What do periodic table groups have in common?

The groups of the periodic table are displayed as vertical columns numbered from 1 to 18. The elements in a group have very similar chemical properties, which arise from the number of valence electrons present—that is, the number of electrons in the outermost shell of an atom .

The arrangement of the elements in the periodic table comes from the electronic configuration of the elements. Because of the Pauli exclusion principle , no more than two electrons can fill the same orbital. The first row of the periodic table consists of just two elements, hydrogen and helium . As atoms have more electrons, they have more orbits available to fill, and thus the rows contain more elements farther down in the table.

The periodic table has two rows at the bottom that are usually split out from the main body of the table. These rows contain elements in the lanthanoid and actinoid series, usually from 57 to 71 ( lanthanum to lutetium ) and 89 to 103 ( actinium to lawrencium ), respectively. There is no scientific reason for this. It is merely done to make the table more compact.

periodic table , in chemistry , the organized array of all the chemical elements in order of increasing atomic number —i.e., the total number of protons in the atomic nucleus. When the chemical elements are thus arranged, there is a recurring pattern called the “periodic law” in their properties, in which elements in the same column (group) have similar properties. The initial discovery, which was made by Dmitry I. Mendeleev in the mid-19th century, has been of inestimable value in the development of chemistry .

It was not actually recognized until the second decade of the 20th century that the order of elements in the periodic system is that of their atomic numbers, the integers of which are equal to the positive electrical charges of the atomic nuclei expressed in electronic units. In subsequent years great progress was made in explaining the periodic law in terms of the electronic structure of atoms and molecules. This clarification has increased the value of the law, which is used as much today as it was at the beginning of the 20th century, when it expressed the only known relationship among the elements.

History of the periodic law

The early years of the 19th century witnessed a rapid development in analytical chemistry—the art of distinguishing different chemical substances—and the consequent building up of a vast body of knowledge of the chemical and physical properties of both elements and compounds . This rapid expansion of chemical knowledge soon necessitated classification , for on the classification of chemical knowledge are based not only the systematized literature of chemistry but also the laboratory arts by which chemistry is passed on as a living science from one generation of chemists to another. Relationships were discerned more readily among the compounds than among the elements; it thus occurred that the classification of elements lagged many years behind that of compounds. In fact, no general agreement had been reached among chemists as to the classification of elements for nearly half a century after the systems of classification of compounds had become established in general use.

J.W. Döbereiner in 1817 showed that the combining weight, meaning atomic weight , of strontium lies midway between those of calcium and barium , and some years later he showed that other such “ triads ” exist (chlorine, bromine , and iodine [halogens] and lithium , sodium , and potassium [alkali metals]). J.-B.-A. Dumas, L. Gmelin, E. Lenssen, Max von Pettenkofer, and J.P. Cooke expanded Döbereiner’s suggestions between 1827 and 1858 by showing that similar relationships extended further than the triads of elements, fluorine being added to the halogens and magnesium to the alkaline-earth metals, while oxygen , sulfur , selenium , and tellurium were classed as one family and nitrogen , phosphorus , arsenic , antimony , and bismuth as another family of elements.

Attempts were later made to show that the atomic weights of the elements could be expressed by an arithmetic function , and in 1862 A.-E.-B. de Chancourtois proposed a classification of the elements based on the new values of atomic weights given by Stanislao Cannizzaro’s system of 1858. De Chancourtois plotted the atomic weights on the surface of a cylinder with a circumference of 16 units, corresponding to the approximate atomic weight of oxygen. The resulting helical curve brought closely related elements onto corresponding points above or below one another on the cylinder, and he suggested in consequence that “the properties of the elements are the properties of numbers,” a remarkable prediction in the light of modern knowledge.

Classification of the elements

In 1864, J.A.R. Newlands proposed classifying the elements in the order of increasing atomic weights, the elements being assigned ordinal numbers from unity upward and divided into seven groups having properties closely related to the first seven of the elements then known: hydrogen , lithium, beryllium , boron , carbon , nitrogen, and oxygen. This relationship was termed the law of octaves, by analogy with the seven intervals of the musical scale.

Then in 1869, as a result of an extensive correlation of the properties and the atomic weights of the elements, with special attention to valency (that is, the number of single bonds the element can form), Mendeleev proposed the periodic law, by which “the elements arranged according to the magnitude of atomic weights show a periodic change of properties.” Lothar Meyer had independently reached a similar conclusion, published after the appearance of Mendeleev’s paper.

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Mendeleev’s Periodic Table

Dmitri Mendeleev ‘s periodic table is the forerunner to the modern periodic table. It is a “ periodic ” table because it groups elements in rows and columns that showcase recurring properties, such as valence, electronegativity, and ionization energy.

• Mendeleev’s first periodic table in 1869 included the 63 known elements and spaces for three predicted, undiscovered elements. He revised and refined this table multiple times, as new data came to light.
• Dmitri Mendeleev did not invent the first periodic table. Instead, he devised a table that organizes elements by atomic weight and periodic properties and predicts properties of undiscovered elements.
• The key difference between Mendeleev’s table and the modern table is that the modern table orders elements by increasing atomic number. To be fair, the proton and atomic number were unknown in Mendeleev’s time and the difference only changes the position of a few elements.

The periodic table is one of the most important tools in chemistry, organizing elements based on their properties and atomic structures. Its development has been a long and complex process, with contributions from many scientists over the centuries. One of the most significant figures in this history is Dmitri Mendeleev, a Russian chemist who first proposed his version of the periodic table in 1869.

Before Mendeleev

Dmitri Mendeleev did not invent the first periodic table , but his table organizes elements much like the table we use today. Mendeleev’s work built on the discoveries of earlier chemists such as John Dalton and Antoine Lavoisier , who laid the foundations of modern chemistry. In the early 19th century, scientists began to investigate the properties of different elements and how they reacted with one another. This led to the development of atomic theory, which proposed that all matter was made up of tiny particles called atoms. By the mid-19th century, scientists had discovered around 60 elements, but there was no systematic way to organize them.

In 1863, John Newlands published a letter in Chemical News , organizing the elements by atomic weight according to his “Law of Octaves”, which is comparable to the modern octet rule . Lothar Meyer’s 1864 book pointed out the recurring or periodic properties in a periodic table organizing elements by their valences.

The story goes that Mendeleev saw the arrangement for his periodic table in a dream. His table orders the elements by increasing atomic weight, in rows and columns, with each column representing a group of elements with similar properties. Mendeleev’s 1869 table surpassed the work of Newlands and Meyer by including all of the 63 known elements and holding spaces for predicted undiscovered elements. The chemical and physical properties of undiscovered elements could be predicted based on periodicity. Specifically, Mendeleev’s periodic table predicted the properties of germanium , gallium, and scandium. Mendeleev also dealt with the lanthanides and actinides by placing them in two separate rows, which is the format that continues in the modern table.

Importance of Mendeleev’s Periodic Table

Mendeleev’s periodic table was a significant breakthrough in chemistry, providing a systematic way to organize the elements and predict their properties. For example, if you have a sample of sodium and understand its properties, you know the properties of lithium (above sodium on the table) and potassium (below sodium) without ever seeing them. All elements in that group (the alkali metals) are highly reactive shiny metals that burn in water and have a +1 oxidation state.

Mendeleev’s table was also a major step forward in understanding atomic structure, as it revealed patterns in the behavior of atoms that had not been noticed before. These patterns reflect the electron shells of atoms. Ultimately, chemical reactions involve interactions between electrons.

Mendeleev’s periodic table allowed scientists to make predictions about elements that had not yet been discovered. Knowing the properties of an unknown elements makes identifying and verifying it a simpler process.

Mendeleev’s Periodic Table vs the Modern Periodic Table

The difference between Mendeleev’s periodic table and the modern periodic table is that Mendeleev’s table ordered elements by increasing atomic weight while the modern table orders elements by increasing atomic number. The atomic weight is the sum of the protons and neutrons in an atom. In contrast, the atomic number is the number of protons. In a few cases, using atomic weight changes the order of elements. This is because of the isotope ratio of naturally occurring elements. But, the concepts of the proton and atomic number were not known in Mendeleev’s time.

Of course, the modern periodic table contains more elements than Mendeleev’s periodic table. The current table has 118 elements, while Mendeleev’s first table had 63.

Mendeleev’s periodic table was a significant breakthrough in chemistry because it offered a systematic way to organize the elements and predict their properties. Further, it allowed scientists to make predictions about elements that had not yet been discovered.

The modern periodic table is based on the concept of atomic number, instead of atomic weight. It includes more elements than Mendeleev’s table, yet still allows for predicting properties of undiscovered elements.

• Godfrey, Simon S. (2003). Dreams & Reality . Trafford Publishing. ISBN 1-4120-1143-4.
• Gordin, Michael (2004). A Well-Ordered Thing: Dmitrii Mendeleev and the Shadow of the Periodic Table . New York: Basic Books. ISBN 978-0-465-02775-0.
• Kak, Subhash (2004). “Mendeleev and the Periodic Table of Elements”. Sandhan . 4 (2): 115–123.
• doi: 10.48550/arXiv.physics/0411080
• Mendeleev, Dmitry Ivanovich; Jensen, William B. (2005). Mendeleev on the Periodic Law: Selected Writings, 1869–1905 . Mineola, New York: Dover Publications. ISBN 978-0-486-44571-7.
• Weeks, Mary Elvira (1956). The Discovery of the Elements (6th ed.). Easton, PA: Journal of Chemical Education.

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