Video Transcript
Which of the following is the
electronic configuration of Ti? (A) Ar 4s1 3d3, (B) Ar 3s2 4d2, (C)
Kr 4s2 3d2, (D) Kr 5s2 4d2, (E) Ar 4s2 3d2.
To solve this problem, we need to
select the answer choice that shows the correct electron configuration of the
element titanium. The electronic configuration of an
atom describes how many electrons the atom has and how these electrons are arranged
into different electron shells and subshells. The atomic number of titanium is
22, which means that a titanium atom has a total of 22 electrons.
When looking at the answer choices,
we see that the electron configurations provided are given in condensed
notation. In general, condensed notation has
the form of the chemical symbol of a noble gas followed by the electron
configuration of the subshells that hold the valence electrons. Titanium is the second
transition-metal element in period four on the periodic table. Let’s use the periodic table to
fill the subshells in a titanium atom with electrons.
Starting with hydrogen and moving
across period one, we fill the 1s subshell with two electrons. So we write 1s2. Moving across period two, we fill
the 2s subshell with two electrons and the 2p subshell with six electrons. So we can write 2s2 2p6. Moving across period three, the
pattern is similar to period two. We will fill the 3s subshell with
two electrons and the 3p subshell with six electrons. So we can write 3s2 3p6. Finally, in period four, we fill
the 4s subshell with two electrons and the 3d subshell with two electrons. So we can write 4s2 3d2.
To write the full electron
configuration for titanium, let’s put the subshells in order from left to right. To determine the identity of the
noble gas which should be used in the condensed notation, we simply locate the noble
gas at the end of the period prior to the period our element is in. Because titanium is in period four,
we look to find the noble gas at the end of period three, which is argon. We can condense the electron
configuration that we wrote for periods one through three as argon in brackets. In other words, the condensed form
of the electron configuration for titanium can be written as argon inside brackets
followed by 4s2 3d2. Therefore, the correct answer is
answer choice (E) argon in brackets 4s2 3d2.
