Ions And Isoelectronic Species: A Chemistry Challenge

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Ions and Isoelectronic Species: A Chemistry Challenge

Hey guys! Let's dive into a cool chemistry question about ions and the number of electrons they have. This is all about understanding how atoms gain or lose electrons to become ions and how some ions can end up having the same number of electrons as noble gases. It's like a chemical identity swap! Let's break it down.

The Question: Finding the Isoelectronic Pair

So, the question asks: Which pair of particles has the same number of electrons?

a) Magnesium cation and argon b) Sodium cation and argon c) Potassium cation and argon d) Chloride anion and neon

We need to figure out which of these pairs has the same number of electrons. This concept is called being isoelectronic. Essentially, we are looking for ions that, after gaining or losing electrons, end up with the electron configuration of a noble gas.

Understanding the Basics: Atoms, Ions, and Electrons

Before we jump into the answer, let's quickly recap some fundamental concepts. An atom is electrically neutral, meaning it has the same number of protons (positive charge) and electrons (negative charge). The number of protons defines what element it is. For example, all atoms with 11 protons are sodium atoms.

An ion is an atom that has gained or lost electrons. When an atom loses electrons, it becomes a positively charged ion, called a cation. When an atom gains electrons, it becomes a negatively charged ion, called an anion. The charge of the ion tells us how many electrons have been gained or lost. For instance, Na+ means a sodium atom has lost one electron, while Cl- means a chlorine atom has gained one electron.

Electrons are the tiny, negatively charged particles that orbit the nucleus of an atom. They determine the chemical properties of an element. Atoms tend to gain or lose electrons to achieve a stable electron configuration, which is often the same as that of a noble gas. Noble gases are super stable because they have a full outermost electron shell.

Analyzing the Options: Step-by-Step

Now, let's analyze each option to determine the number of electrons in each particle.

a) Magnesium Cation (Mg²⁺) and Argon (Ar)

  • Magnesium (Mg) has an atomic number of 12, meaning a neutral magnesium atom has 12 electrons.
  • The Mg²⁺ cation has lost two electrons, so it has 12 - 2 = 10 electrons.
  • Argon (Ar) has an atomic number of 18, meaning it has 18 electrons.

So, Mg²⁺ has 10 electrons, and Ar has 18 electrons. They are not isoelectronic.

b) Sodium Cation (Na⁺) and Argon (Ar)

  • Sodium (Na) has an atomic number of 11, meaning a neutral sodium atom has 11 electrons.
  • The Na⁺ cation has lost one electron, so it has 11 - 1 = 10 electrons.
  • Argon (Ar), as we know, has 18 electrons.

Again, Na⁺ has 10 electrons, and Ar has 18 electrons. They are not isoelectronic.

c) Potassium Cation (K⁺) and Argon (Ar)

  • Potassium (K) has an atomic number of 19, meaning a neutral potassium atom has 19 electrons.
  • The K⁺ cation has lost one electron, so it has 19 - 1 = 18 electrons.
  • Argon (Ar) has 18 electrons.

In this case, K⁺ has 18 electrons, and Ar also has 18 electrons. They are isoelectronic!

d) Chloride Anion (Cl⁻) and Neon (Ne)

  • Chlorine (Cl) has an atomic number of 17, meaning a neutral chlorine atom has 17 electrons.
  • The Cl⁻ anion has gained one electron, so it has 17 + 1 = 18 electrons.
  • Neon (Ne) has an atomic number of 10, meaning it has 10 electrons.

So, Cl⁻ has 18 electrons, and Ne has 10 electrons. They are not isoelectronic.

The Answer: Why Option C is Correct

The correct answer is (c) potassium cation and argon. Both the K⁺ cation and the Ar atom have 18 electrons. This is because potassium loses one electron to achieve the same electron configuration as argon, making them isoelectronic. The potassium ion (K⁺) achieves the stable electron configuration of argon by losing its outermost electron.

Digging Deeper: Isoelectronic Species and Stability

The concept of isoelectronic species is closely tied to the idea of chemical stability. Atoms are most stable when they have a full outermost electron shell. This is why elements in group 18, the noble gases, are so unreactive. They already have a full outermost shell!

Atoms will gain or lose electrons to achieve this stable electron configuration. For example, sodium (Na) readily loses one electron to form Na⁺, which has the same electron configuration as neon (Ne). Similarly, chlorine (Cl) readily gains one electron to form Cl⁻, which has the same electron configuration as argon (Ar).

Understanding isoelectronic species helps us predict the types of ions that elements will form. Elements in group 1 (alkali metals) tend to form +1 ions, elements in group 2 (alkaline earth metals) tend to form +2 ions, and elements in group 17 (halogens) tend to form -1 ions. These ions are all isoelectronic with the nearest noble gas, making them more stable than the neutral atoms.

Why Other Options are Incorrect

Let's quickly recap why the other options are incorrect:

  • a) Magnesium cation and argon: Mg²⁺ has 10 electrons, while Ar has 18 electrons.
  • b) Sodium cation and argon: Na⁺ has 10 electrons, while Ar has 18 electrons.
  • d) Chloride anion and neon: Cl⁻ has 18 electrons, while Ne has 10 electrons.

In each of these cases, the number of electrons in the two species is different, so they are not isoelectronic.

In Conclusion: Mastering Electron Counts

Understanding how to count electrons in atoms and ions is a fundamental skill in chemistry. By mastering this skill, you can predict the types of ions that elements will form, understand the concept of isoelectronic species, and gain a deeper understanding of chemical stability. So, keep practicing, and you'll become an electron-counting pro in no time! Keep rocking the chemistry world, guys!