Problem 141
Question
According to the periodic law of elements, the variation in properties of elements is related to their (a) atomic masses (b) nuclear masses (c) atomic numbers (d) nuclear neutron-proton number ratios
Step-by-Step Solution
Verified Answer
The variation in properties of elements is related to their atomic numbers (c).
1Step 1: Understand the Periodic Law
The periodic law states that the properties of elements are a periodic function of their atomic numbers. A modern periodic table organizes elements based on increasing atomic numbers, not atomic or nuclear masses, nor neutron-proton ratios.
2Step 2: Analyze the Options
- **(a) Atomic masses**: Previously, the periodic table was based on atomic masses, but this led to some inconsistencies.
- **(b) Nuclear masses**: The mass of an atomic nucleus also does not align with periodic properties.
- **(c) Atomic numbers**: Current periodic law uses atomic numbers for organization, correlating with element properties.
- **(d) Nuclear neutron-proton number ratios**: This ratio does not dictate periodic properties.
3Step 3: Choose the Correct Answer
Since the modern periodic table and periodic law use atomic numbers to organize and predict element properties, (c) atomic numbers, are the correct answer.
Key Concepts
Atomic NumberModern Periodic TableElement Properties
Atomic Number
The atomic number of an element is crucial in understanding its identity and properties. It is defined as the number of protons found in the nucleus of an atom of the element. Since protons are positively charged, the atomic number also determines the element's electrical charge in a neutral atom, where protons equal the number of electrons. This number is unique for each element and usually helps distinguish one element from another.
In the periodic table, elements are arranged in the order of increasing atomic numbers. This system ensures a clear, logical structure, where properties of elements can be anticipated based on their positions. By knowing an element's atomic number, you can also determine the element's position on the table, its reactivity, its possible bonding behavior, and much more.
This critical concept replaced the earlier Mendeleev's table, which organized elements by atomic masses, with atomic numbers showing greater consistency in reflecting element properties. Thus, atomic numbers form the backbone of understanding the chemistry of elements and their place in the periodic table.
In the periodic table, elements are arranged in the order of increasing atomic numbers. This system ensures a clear, logical structure, where properties of elements can be anticipated based on their positions. By knowing an element's atomic number, you can also determine the element's position on the table, its reactivity, its possible bonding behavior, and much more.
This critical concept replaced the earlier Mendeleev's table, which organized elements by atomic masses, with atomic numbers showing greater consistency in reflecting element properties. Thus, atomic numbers form the backbone of understanding the chemistry of elements and their place in the periodic table.
Modern Periodic Table
The modern periodic table is a universal tool used by scientists to understand elements and predict their behaviors. It's organized in a systematic manner, primarily based on increasing atomic numbers, which as mentioned, is the number of protons in an element. This organization comes from the periodic law, which states that the properties of elements are a periodic function of their atomic numbers.
Here's a simplified breakdown of the table's organization:
This table is not limited to chemistry; it's a cross-disciplinary tool useful in physics, biology, and environmental studies, highlighting the interconnectedness of elemental properties and their applications across different science fields.
Here's a simplified breakdown of the table's organization:
- **Periods**: These are the horizontal rows in the table, where elements show a progression of properties as atomic numbers increase.
- **Groups**: These are the vertical columns, with elements having similar chemical properties due to having the same number of outer-shell electrons.
This table is not limited to chemistry; it's a cross-disciplinary tool useful in physics, biology, and environmental studies, highlighting the interconnectedness of elemental properties and their applications across different science fields.
Element Properties
The properties of elements emerge from their atomic structures, and these properties can often be predicted based on their position on the periodic table. They can be categorized into three main types: physical, chemical, and atomic properties. Let's delve into what these mean:
- **Physical Properties**: These include characteristics like melting and boiling points, density, and atomic radius. Physical properties are observed without changing the substance’s chemical identity.
- **Chemical Properties**: These refer to an element's ability to undergo chemical changes or reactions due to its electron configuration, such as reactivity, electronegativity, and ionization energy.
- **Atomic Properties**: These are traits directly related to an atom's structure, including atomic size, ionization energy, and electron affinity.
The periodic table organizes elements so that these properties exhibit periodic trends. For instance, as you move across a period from left to right, atomic radii tend to decrease, while electronegativity increases. In groups, as you move down, the situation often reverses, with elements showing larger atomic radii and decreased electronegativity.
Through patterns within the periodic table, scientists can predict element behavior and reactions, without needing an exhaustive analysis for each new compound studied. This predictive power makes the periodic table an invaluable scientific tool.
- **Physical Properties**: These include characteristics like melting and boiling points, density, and atomic radius. Physical properties are observed without changing the substance’s chemical identity.
- **Chemical Properties**: These refer to an element's ability to undergo chemical changes or reactions due to its electron configuration, such as reactivity, electronegativity, and ionization energy.
- **Atomic Properties**: These are traits directly related to an atom's structure, including atomic size, ionization energy, and electron affinity.
The periodic table organizes elements so that these properties exhibit periodic trends. For instance, as you move across a period from left to right, atomic radii tend to decrease, while electronegativity increases. In groups, as you move down, the situation often reverses, with elements showing larger atomic radii and decreased electronegativity.
Through patterns within the periodic table, scientists can predict element behavior and reactions, without needing an exhaustive analysis for each new compound studied. This predictive power makes the periodic table an invaluable scientific tool.
Other exercises in this chapter
Problem 140
\(\mathrm{Ce}^{3+}, \mathrm{La}^{3+}, \mathrm{Pm}^{3+}\) and \(\mathrm{Yb}^{3+}\) have ionic radii in the in creasing order as (a) \(\mathrm{La}^{3+}
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The lanthanide contraction is responsible for the fact that \([\mathbf{2 0 0 5}]\) (a) \(\mathrm{Zr}\) and \(\mathrm{Y}\) have about the same radius (b) \(\math
View solution Problem 141
Which of the following factors may be regarded as the main cause of lanthanide contraction? \(\quad\) [2005] (a) poor shielding of one of 4 f electrons by anoth
View solution Problem 142
A reduction in atomic sizes with increase in atomic number is a characteristic of element of \(\quad\) [2003] (a) high atomic masses (b) d-block (c) f-block (d)
View solution