Without referring to a periodic table, pick the electron configuration of elements with the following atomic numbers and classify the elements. (Type your answer in noble gas notation using the format [Ar] 4s2 3d10 4p2 for [Ar]4s23d104p2.)
(a) 17
(b) 20
(c) 23
17 must be in group 7 and have 7 electrons in the outside shell. So that makes it a halogen. It's one element short of Ar(which you should know is Ar and that makes it sure bet to be Cl. So I would write [Ne] (which is 10) 3s2 3p5.
The others are done the same way.
20 must be two after Ar and in group 2 and that would make it [Ar]4s2. Element 23 must be in the 3d transition series so it is just 3 more than Ca. Where would those extra three electrons go?
(a) To determine the electron configuration of an element with atomic number 17, we can refer to the periodic table or use the Aufbau principle, which states that electrons fill orbitals in order of increasing energy.
The atomic number of 17 corresponds to the element chlorine (Cl). The electron configuration can be determined as follows:
1s2 2s2 2p6 3s2 3p5
However, we are asked to write it in noble gas notation. The noble gas preceding chlorine in the periodic table is neon (Ne), which has the electron configuration [He] 2s2 2p6.
Thus, the noble gas notation for chlorine is:
[Ne] 3s2 3p5
(b) The atomic number of 20 corresponds to the element calcium (Ca). The electron configuration is:
1s2 2s2 2p6 3s2 3p6 4s2
In noble gas notation, we can use the noble gas that comes before calcium in the periodic table, which is argon (Ar). Its electron configuration is [Ar] 3d10 4s2.
Therefore, the noble gas notation for calcium is:
[Ar] 4s2
(c) The atomic number of 23 corresponds to the element vanadium (V). The electron configuration can be determined as:
1s2 2s2 2p6 3s2 3p6 4s2 3d3
In noble gas notation, we can use the noble gas that comes before vanadium in the periodic table, which is argon (Ar). Its electron configuration is [Ar] 3d10 4s2.
Therefore, the noble gas notation for vanadium is:
[Ar] 3d3
To determine the electron configuration and classify the elements without referring to a periodic table, you can follow the principles of electron filling order and the periodic table's structure.
(a) For the element with atomic number 17, we start by knowing that it belongs to the group of elements called halogens. The halogens have 7 valence electrons, which means they belong to the 7th column (group 17) of the periodic table. To determine the electron configuration, we need to fill up the electron orbitals from lowest to highest energy levels.
The electron filling order goes as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, and so on.
Since atomic number 17 corresponds to the element in group 17, it has 17 electrons. Following the electron filling order, we can distribute the electrons as follows:
1s2 2s2 2p6 3s2 3p5.
However, to write it in noble gas notation, we can use the electron configuration of the noble gas that comes before atomic number 17, which is argon (Ar).
Therefore, the electron configuration for the element with atomic number 17 is [Ar] 4s2 3d10 4p5.
(b) For the element with atomic number 20, we know that it belongs to the group of elements called alkaline earth metals. Alkaline earth metals have 2 valence electrons, which means they belong to the 2nd column (group 2) of the periodic table.
Following the electron filling order, we can distribute the electrons for atomic number 20 as:
1s2 2s2 2p6 3s2 3p6 4s2.
In this case, we don't need to use the noble gas notation because there are no noble gases before atomic number 20.
Therefore, the electron configuration for the element with atomic number 20 is 1s2 2s2 2p6 3s2 3p6 4s2.
(c) For the element with atomic number 23, we start by knowing that it belongs to the transition metals group. Transition metals are filled in a more complex manner, as they involve the 3d and 4s orbitals.
Following the electron filling order, we can distribute the electrons for atomic number 23 as:
1s2 2s2 2p6 3s2 3p6 4s2 3d3.
Again, there is no need to use noble gas notation since no noble gases come before atomic number 23.
Therefore, the electron configuration for the element with atomic number 23 is 1s2 2s2 2p6 3s2 3p6 4s2 3d3.