Question

For each element, count the number of valence electrons, core electrons, and unpaired electrons in the ground state: (a) carbon, (b) phosphorus, (c) neon.

Short answer

For the given elements in their ground state: (a) Carbon has 4 valence electrons, 2 core electrons, and 2 unpaired electrons; (b) Phosphorus has 5 valence electrons, 10 core electrons, and 3 unpaired electrons; (c) Neon has 8 valence electrons, 2 core electrons, and 0 unpaired electrons.

Step-by-step solution

(a) Carbon

Step 1: Determine the electron configuration Carbon has an atomic number of 6, meaning it has 6 electrons in its neutral state. The electron configuration is given by: 1s² 2s² 2p² Step 2: Identify valence and core electrons Valence electrons are the electrons in the outermost shell of an atom. In this case, carbon has 4 valence electrons (2s² and 2p²). The remaining 2 electrons (1s²) are core electrons. Step 3: Determine unpaired electrons Unpaired electrons are electrons without a full set of paired electrons. Here, carbon has 2 unpaired electrons (2p²). So, for carbon: - Valence electrons: 4 - Core electrons: 2 - Unpaired electrons: 2

(b) Phosphorus

Step 1: Determine the electron configuration Phosphorus has an atomic number of 15, meaning it has 15 electrons in its neutral state. The electron configuration is given by: 1s² 2s² 2p⁶ 3s² 3p³ Step 2: Identify valence and core electrons Phosphorus has 5 valence electrons (3s² and 3p³). The remaining 10 electrons (1s², 2s², and 2p⁶) are core electrons. Step 3: Determine unpaired electrons Unpaired electrons are electrons without a full set of paired electrons. Here, phosphorus has 3 unpaired electrons (3p³). So, for phosphorus: - Valence electrons: 5 - Core electrons: 10 - Unpaired electrons: 3

(c) Neon

Step 1: Determine the electron configuration Neon has an atomic number of 10, meaning it has 10 electrons in its neutral state. The electron configuration is given by: 1s² 2s² 2p⁶ Step 2: Identify valence and core electrons Neon has 8 valence electrons (2s² and 2p⁶). The 2 remaining electrons (1s²) are core electrons. Step 3: Determine unpaired electrons Since neon has a full set of paired electrons in the 2s and 2p orbitals, it has 0 unpaired electrons. So, for neon: - Valence electrons: 8 - Core electrons: 2 - Unpaired electrons: 0