Question

How many unpaired electrons are there in the following atoms? (a) aluminum (b) argon (c) arsenic

Short answer

Answer: Aluminum has 1 unpaired electron, argon has 0 unpaired electrons, and arsenic has 3 unpaired electrons.

Step-by-step solution

Determine the atomic numbers

First, we need to find the atomic numbers of aluminum, argon, and arsenic. The atomic number represents the number of protons and electrons in a neutral atom. These numbers can be easily found in the periodic table: (a) Aluminum (Al) - Atomic Number 13 (b) Argon (Ar) - Atomic Number 18 (c) Arsenic (As) - Atomic Number 33

Write the electron configurations

We will now write the electron configurations of the atoms: (a) Aluminum (Al) - Atomic Number 13: 1s^2 2s^2 2p^6 3s^2 3p^1 (b) Argon (Ar) - Atomic Number 18: 1s^2 2s^2 2p^6 3s^2 3p^6 (c) Arsenic (As) - Atomic Number 33: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^3

Identify the unpaired electrons

We will examine the electron configurations and identify the unpaired electrons in each atom: (a) Aluminum (Al): In the 3p subshell, there is one electron (3p^1), so there is 1 unpaired electron. (b) Argon (Ar): All subshells are completely filled (1s^2, 2s^2, 2p^6, 3s^2, 3p^6). Therefore, there are no unpaired electrons. (c) Arsenic (As): In the 4p subshell, there are three electrons (4p^3). 3 electrons imply there are three half-filled orbitals, so there are 3 unpaired electrons.

State the final answer

Using the analysis from the steps above, we can now state the number of unpaired electrons for each atom: (a) Aluminum (Al) - 1 unpaired electron (b) Argon (Ar) - 0 unpaired electrons (c) Arsenic (As) - 3 unpaired electrons