Question

What is the Lewis symbol for each of the following atoms or ions: (a) \(K,(b) A s,(c) S n^{2+},\left(\right.\) d) \(N^{3-} ?\)

Short answer

The Lewis symbols for the given atoms or ions are: (a) K: \[\mathrm{K \cdot}\], (b) As: \[\mathrm{As:}\], (c) Sn²⁺: \[\mathrm{Sn^{2+}::}\], and (d) N³⁻: \[\mathrm{N^{3-}:::}\].

Step-by-step solution

(a) Lewis symbol for K (Potassium)

Potassium is an alkali metal with an atomic number of 19. Its electron configuration is 1s²2s²2p⁶3s²3p⁶4s¹, meaning it has one valence electron. The Lewis symbol for potassium would be the chemical symbol 'K' surrounded by one dot. So the Lewis symbol for potassium is \[\mathrm{K \cdot}\]

(b) Lewis symbol for As (Arsenic)

Arsenic has an atomic number of 33, with an electron configuration of 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p³. Arsenic has 5 valence electrons, present in the 4p orbitals. The Lewis symbol for arsenic will have the chemical symbol 'As' surrounded by 5 dots. So the Lewis symbol for arsenic is \[\mathrm{As:}\]

(c) Lewis symbol for Sn²⁺ (Tin ion with a +2 charge)

Tin is a metal with an atomic number of 50. Its electron configuration is 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p². In its 2+ ionic form, tin loses two electrons from the 5p orbital. Consequently, its electron configuration becomes 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰. With 4 valence electrons left, the Lewis symbol for Sn²⁺ has four dots around the symbol 'Sn'. So the Lewis symbol for Sn²⁺ is \[\mathrm{Sn^{2+}::}\]

(d) Lewis symbol for N³⁻ (Nitrogen ion with a -3 charge)

Nitrogen is a non-metal with an atomic number of 7. Its electron configuration is 1s²2s²2p³, which gives it 5 valence electrons. In its 3- ionic form, nitrogen gains 3 additional electrons in the 2p orbital to complete the octet. The electron configuration for N³⁻ is 1s²2s²2p⁶ with 8 valence electrons. The Lewis symbol for N³⁻ has 8 dots surrounding 'N'. So the Lewis symbol for N³⁻ is \[\mathrm{N^{3-}:::}\]

Key concepts

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a critical role in chemical bonding and reactions. These electrons reside in the highest energy level (or shell) and are the ones involved in forming bonds with other atoms. For example:

• Potassium (K), which has an atomic number of 19, has a single valence electron in its 4s subshell.
• Arsenic (As), with an atomic number of 33, has five valence electrons in the 4s and 4p subshells.
• Sn²⁺ or the +2 ion of tin loses two electrons, leaving it with four valence electrons.
• N^3– or the nitrogen ion gains three electrons, completing its octet with eight valence electrons.

A clear understanding of valence electrons helps in predicting how atoms will interact and form bonds with each other.

Electron Configuration

Electron configuration describes the arrangement of electrons in an atom. It follows the order in which electrons populate the atomic orbitals to achieve the lowest possible energy state, often described by the notation of subshells, such as 1s, 2s, 2p, etc.

• The electron configuration of potassium is 1s²2s²2p⁶3s²3p⁶4s¹, indicating a single electron beyond a full 3p subshell.
• In arsenic, with the configuration 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p³, electrons fill up to the 4p subshell, showing the typical filling order.
• Sn²⁺ starts with tin’s full neutral configuration and loses two electrons, emptying the 5p subshell for its cation state.
• For N^3–, an additional three electrons fill into the 2p orbitals, resulting in a filled octet.

This configuration helps us understand the stability and reactivity of elements and their ions.

Ions

Ions occur when an atom gains or loses electrons, resulting in a net charge. This process is vital for the formation of ionic compounds and directly influences the chemical properties of the substance.

• A cation, like Sn²⁺, is formed when tin loses two electrons, leading to a positive charge.
• An anion such as N^3– is formed when nitrogen gains electrons, resulting in a negative charge.

Studying ions helps us understand various chemical reactions and phenomena like conductivity in solutions, and it is essential for explaining aspects of electrochemistry and catalysis.

Chemical Symbols

Chemical symbols are concise notations representing elements in the periodic table. They are usually one or two letters with the first letter capitalized, sometimes accompanied by a charge to indicate ions.

• K stands for potassium, an alkali metal known for having a single valence electron.
• As denotes arsenic, highlighting its nonmetallic properties with half-filled p orbitals.
• Sn refers to tin, easily forming cations like Sn²⁺ in reactions.
• N signifies nitrogen, which can gain electrons to become N^3–, completing its valence shell.

Chemical symbols are integral to writing chemical equations and expressing molecular compositions succinctly.