Question

A nuclide of an alkaline earth metal undergoes radioactive decay by emission of the \(\alpha\) particle in succession. The group of the periodic table to which the resulting daughter element would belong is (a) Gp 14 (b) Gp 6 (c) Gp 16 (d) Gp 4

Short answer

Gp 14 (option a)

Step-by-step solution

Understanding the Alpha Particle

An alpha particle consists of 2 protons and 2 neutrons, meaning it has a total atomic mass number of 4 and an atomic number of 2.

Initial Element Explanation

Alkaline earth metals belong to Group 2 in the periodic table. They have two valence electrons and typically have an atomic number represented by 'Z' and an atomic mass number denoted by 'A'.

Effect of Alpha Decay

When a nuclide undergoes alpha decay, it loses an alpha particle, thereby reducing its atomic number by 2 and its mass number by 4. This can be represented as: new atomic number = Z - 2, new mass number = A - 4.

Determine Resulting Group

Given that the original element was in Group 2, after the emission of an alpha particle, the atomic number decreases by 2. The resulting daughter element will therefore belong to Group 14 (since Group 2 elements like Magnesium (Z=12) become elements like Neon (Z=10) when 2 protons are lost).

Key concepts

Alpha Decay

Alpha decay is a type of radioactive decay where a nucleus emits an alpha particle, which consists of 2 protons and 2 neutrons. This process is common in heavy elements and causes the parent nucleus to lose not only mass but also a part of its identity since the atomic number decreases. When a nucleus undergoes alpha decay:

• It loses an alpha particle.
• The atomic number decreases by 2.
• The mass number decreases by 4.

For instance, if we consider an element with atomic number 88 and mass number 226, after alpha decay, it will become an element with atomic number 86 and mass number 222. This process significantly alters the chemical properties of the element.

Periodic Table Groups

The periodic table is arranged in a systematic way of elements in rows and columns, which groups elements with similar chemical properties together. These columns are known as groups. Each group contains elements that have the same number of valence electrons, which influences their chemical behavior strongly. To understand how the periodic table operates:

• Groups are numbered from 1 to 18.
• Elements in the same group exhibit similar chemical reactions, due to their electron configuration.
• Moving from left to right across a period of the periodic table, the properties of elements gradually change.

The knowledge of periodic table groups is essential when analyzing chemical reactions, and predicting the behavior of elements after processes like radioactive decay.

Alkaline Earth Metals

Alkaline earth metals are a group of elements in Group 2 of the periodic table. They include Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium. Known for being shiny and quite reactive, they play a significant role in various chemical reactions. Some key features of alkaline earth metals include:

• They have two electrons in their outer shell.
• They readily lose these two electrons to form a +2 charge, making them highly reactive.
• They form basic (alkaline) solutions in water.

Particularly, when these metals undergo processes like alpha decay, they transform into different elements with unique properties, dramatically shifting their position on the periodic table.

Atomic Number

The atomic number of an element is a crucial concept in chemistry. It determines the unique identity of an element, as it represents the number of protons in a nucleus. This number is always whole and is located above the element symbol in the periodic table. Understanding the atomic number:

• Each element has a distinct atomic number, for example, Hydrogen has an atomic number of 1.
• The atomic number defines the position of an element on the periodic table.
• When an element undergoes alpha decay, the atomic number decreases by 2, reflecting the emission of 2 protons.

Hence, the atomic number is fundamental not only in identifying an element but also in understanding how elements evolve through nuclear reactions like radioactive decay.

Mass Number

Mass number is slightly different from atomic number as it considers both protons and neutrons in the nucleus. It is represented as the sum total of these particles, influencing the isotope of an element. In practical terms:

• The mass number is typically written after the element name, e.g., Carbon-14.
• Elements of the same atomic number can have different mass numbers, leading to different isotopes.
• In alpha decay, the loss of two protons and two neutrons results in the mass number decreasing by 4.

Understanding the mass number is crucial for nuclear chemistry and physics, as it helps to grasp how isotopes are formed and how they behave under various reactions, including radioactive decay.