Chapter 2: Problem 2
On what basis did Mendeleev construct his periodic table? On what basis are the elements arranged in the modern periodic table?
Short Answer
Expert verified
Mendeleev constructed his periodic table based on atomic masses and the periodicity of elements, while the modern periodic table is arranged by increasing atomic number and reflects the electronic configuration of atoms.
Step by step solution
01
Understanding Mendeleev's Periodic Table
To understand how Mendeleev constructed his periodic table, identify that Mendeleev arranged the elements based on their atomic masses. He observed that when elements are arranged in order of increasing atomic mass, certain types of elements regularly occurred. For example, he noted that elements with similar properties appeared at regular intervals, which he referred to as the 'periodicity' of elements.
02
Understanding the Modern Periodic Table
To understand the arrangement of the modern periodic table, recognize that elements are organized by increasing atomic number, not atomic mass. The atomic number is the number of protons in an atom's nucleus, which is unique to each element and determines its identity. The modern periodic table also reflects the electronic configuration of atoms, which influences the chemical properties of the elements and results in the periodic trends observed across the table, such as electronegativity, ionization energy, and atomic radius.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Mendeleev’s Periodic Law
Mendeleev's Periodic Law paved the way for our modern understanding of the chemical elements. Dimitri Mendeleev, a Russian chemist, introduced a revolutionary arrangement of the chemical elements in 1869. He based his periodic table on atomic mass, listing the elements in order of increasing mass and grouping them by their chemical properties. Most notably, Mendeleev left gaps in his table, predicting the existence and properties of elements that had not yet been discovered. His law stated that the properties of the elements are a periodic function of their atomic masses. This concept displayed a profound understanding of the patterns within chemical behavior, which helped scientists make sense of how elements interact with one another.
However, there were a few anomalies in Mendeleev's table due to wrong atomic masses of some elements, and later it was realized that atomic number is a more fundamental property than atomic mass. This realization led to the modern periodic law, which refines Mendeleev's concept with a contemporary twist.
However, there were a few anomalies in Mendeleev's table due to wrong atomic masses of some elements, and later it was realized that atomic number is a more fundamental property than atomic mass. This realization led to the modern periodic law, which refines Mendeleev's concept with a contemporary twist.
Atomic Mass
Atomic mass is an essential concept in chemistry that represents the mass of an atom, typically measured in atomic mass units (amu). It is an average, taking into account the various isotopes of an element that may exist, each with a different number of neutrons in the nucleus. The atomic mass impacts the physical and chemical properties of the element, including its density and how it reacts with other elements.
While Mendeleev's periodic table was based on atomic mass, this measurement alone did not account for the full behavior of atoms. However, it played an integral role in initial observations of periodicity and the classification of the elements during Mendeleev's time.
While Mendeleev's periodic table was based on atomic mass, this measurement alone did not account for the full behavior of atoms. However, it played an integral role in initial observations of periodicity and the classification of the elements during Mendeleev's time.
Atomic Number
The atomic number is a fundamental characteristic of an element, defining its unique identity. It represents the number of protons found in the nucleus of an atom and is denoted by the symbol 'Z'. Unlike atomic mass, the atomic number is not subject to variation; each element has only one atomic number. When elements are arranged in order of increasing atomic number, a clear pattern can be observed in their physical and chemical properties, which is the basis for the modern periodic table. This property provides a more reliable means of classifying elements than atomic mass, which led to the revision of the original Mendeleev periodic table.
Electronic Configuration
Electronic configuration refers to the distribution of electrons in an atom or molecule. It describes how the electrons are organized into various atomic orbitals, and is fundamental to understanding the chemical behavior of an element. The modern periodic table is arranged in such a way that elements with similar electron configurations are grouped together, leading to similar chemical properties. This element arrangement allows the prediction of element behavior during chemical reactions.
The periodicity of these configurations results in recurring patterns of properties, such as valency and bonding preferences, which are extremely useful in the study of chemistry. Elements in the same group typically have the same number of electrons in their outer shell, leading to similar reactivity patterns.
The periodicity of these configurations results in recurring patterns of properties, such as valency and bonding preferences, which are extremely useful in the study of chemistry. Elements in the same group typically have the same number of electrons in their outer shell, leading to similar reactivity patterns.
Periodicity of Elements
Periodicity in chemistry refers to the recurring trends that are observed in the properties of the elements. It is the principle that enabled the development of the periodic table. When elements are arranged in increasing atomic number, groups of elements with similar chemical properties appear at regular intervals or periods. These properties include a variety of attributes such as reactivity, melting and boiling points, as well as metallic or nonmetallic character.
The periodicity is rooted in the elements' electronic configurations, as atoms with the same number of valence electrons tend to exhibit similar characteristics. This regular pattern helps chemists predict the behavior of unknown elements and their compounds.
The periodicity is rooted in the elements' electronic configurations, as atoms with the same number of valence electrons tend to exhibit similar characteristics. This regular pattern helps chemists predict the behavior of unknown elements and their compounds.
Periodic Trends
In the exploration of periodic trends, scientists analyze how different elemental characteristics increase or decrease across a period (horizontal row) or down a group (vertical column) in the periodic table. These trends are directly related to electronic configuration and the atomic structure of the elements. Some key periodic trends include atomic radius, ionization energy, electronegativity, and electron affinity.
- Atomic radius generally decreases across a period and increases down a group.
- Ionization energy, the energy required to remove an electron from an atom, typically increases across a period and decreases down a group.
- Electronegativity, the tendency of an atom to attract electrons, often increases across a period and decreases down a group.