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The order in which electrons fill atomic orbitals is based on the Aufbau Principle. Aufbau is German for "building up", and the principle simply states that electrons will occupy the lowest energy orbitals first because having a low energy is more stable. So on the surface, the fill order (i.e. which orbitals are filled in which order) simply reflects the energies of the orbitals from lowest to highest.
Now if your question is really referring to the seemingly screwy order that the orbitals fill (4s filling before the 3d... 6s filling before any of the 4f's), then we need to delve a bit deeper into why the energy of the 4s orbital is lower than that of the 3d, and so on.
In a 1-electron atom (like H, He+, Li2+, Be3+, etc.) the energies of the orbitals depend only two things---the charge of the nucleus, and how far away the electron is. Since the average distance that an electron is from the nucleus is defined by its principle quantum number (n), all the orbitals with a particular quantum number have the same energy (we call them degenerate). So in hydrogen, the 1s orbital has the lowest energy, then comes the 2s and the three 2p orbitals---all with exactly the same energy. Next we have the 3s, 3p's and 3d's---again all with the same energy and so on. So in a 1-electron atom, there is no preference of 2s over 2p (they have the same energy), and definitely not 4s over 3d, because the 4s orbital is higher in energy than the 3d in a 1-electron atom. So how come things are so different in a multi-electron atom?
The answer boils down to two phenomena---shielding and penetration. Shielding is the repulsive effect that inner electrons have on outer electrons. For instance, if I am a valence electron in the 4s orbital of a potassium atom and I am looking inward at the nucleus, I feel the positive charge of the 19 protons in the nucleus, but I am also being repelled by the 18 electrons (2 in the first shell, 8 in the 2nd shell, and 8 in the third shell) that sit between me and the nucleus. Those 18 electrons are shielding me from much of the nuclear charge.
Penetration is the ability for some electrons to skip closer to the nucleus for brief periods of time. An electron in a particular orbital has the ability to penetrate into the same regions of the electron cloud as other electrons of the same orbital type. So for instance, as a 4s electron, I have the ability to spend brief periods of time in the same regions of the atom where one would find the 3s, 2s, and 1s electrons. Mind you, that doesn't mean my average distance from the nucleus is any less than it would be if I were a 4p or 4d or 4f orbital---that "4" means I am in the 4th shell and so I have the same average distance as all those other orbitals. But because the 4s can spend brief periods of time penetrating close to the nucleus, it is capable of AVOIDING SHIELDING!!
Think about it... if I as a 4s electron can penetrate all the way down to the 1s region, that means I am completely unshielded (no electrons between me and the nucleus, sitting next to 19 protons. If I penetrate down to the 2s region, that means I am only shielded by the two 1s electrons, and so on. This effect has such a big influence on the energy of those 4s electrons, that the energy is actually less than it would be if they were in 3d orbitals. The 3d is the first set of d orbitals---there is no 2d or 1d, so they cannot penetrate anywhere---they will always be stuck on the outside of 18 electrons looking in. I tend to liken this to being at a rock concert, and getting seats many many rows behind your friends. You might think that your experience is somewhat lessened by being so far back, but what if for a brief period of time you got to penetrate all the way up to the stage and hang out with the band? Who has a better experience then?
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Why is not there 3d2 instead of 4s2?
In the electron configuration of an atom, the 4s orbital is generally filled before the 3d orbital due to the lower energy level of the 4s orbital. This follows the Aufbau principle, where electrons fill orbitals in order of increasing energy. Thus, in the electron configuration of an atom, the 4s orbital is filled before the 3d orbital, leading to the configuration 4s2 instead of 3d2.
Are lines and arrows used to inicate electron configuration?
Yes, lines and arrows can be used to indicate electron configuration. Arrows are usually used to represent electrons, while lines can be used to show the energy levels of electrons or the order in which they fill orbitals.
What is the orbital of the element yttrium?
The valence electrons fill in 4d orbital The electron configuration of yttrium is [Kr]4d15s2.
Are elements arranged according to blocks corresponding to the orbitals being filled?
Yes, elements are arranged in the periodic table according to blocks that correspond to the orbitals being filled. For example, the s-block elements fill the s-orbital, the p-block elements fill the p-orbital, the d-block elements fill the d-orbital, and the f-block elements fill the f-orbital. This organization provides a structured way to represent the electron configurations of elements.
How many electrons in hydrogen valence shell will give it a noble gas configuration?
Two electrons will fill a hydrogen's outer, or valence, shell.
What is wrong with 1s22s22p63s23p64s24d104p6?
The electron configuration provided seems to be incorrect. The correct electron configuration for an element is based on the Aufbau principle, which governs the way electrons fill energy levels and sublevels. Double-check the electron configuration using the correct order of filling for orbitals.
How many bonds will nitrogen have to form to fill its outer energy level?
Nitrogen would have three bonds in order to fill its valence shell.
How many electrons does a nitrogen atom need to gain in order to attain noble-gas electrons configuration?
A nitrogen atom needs to gain 3 electrons in order to attain a noble-gas electron configuration, similar to that of neon. This would allow the nitrogen atom to fill its outermost energy level and achieve greater stability.
How are electrons arranged in the atom?
Electrons are arranged in energy levels or shells around the nucleus of an atom. The first shell can hold up to 2 electrons, while the second and third shells can hold up to 8 electrons each. The electrons fill up the shells in order of increasing energy levels.
Why is not there 3d2 instead of 4s2?
In the electron configuration of an atom, the 4s orbital is generally filled before the 3d orbital due to the lower energy level of the 4s orbital. This follows the Aufbau principle, where electrons fill orbitals in order of increasing energy. Thus, in the electron configuration of an atom, the 4s orbital is filled before the 3d orbital, leading to the configuration 4s2 instead of 3d2.
Why is the electronic configuration of uranium Rn 5f3 6d1 7s2?
The electronic configuration of uranium is Rn 5f3 6d1 7s2 because uranium has 92 electrons. Electrons fill up the orbitals with the lowest energy level first (Aufbau principle), and the 5f, 6d, and 7s orbitals are progressively filled in that order for uranium.
A supplier must fill four large orders How many different ways can those orders be arranged?
i am doing this same question for a stats midterm and i am thinking that it is chronological, numerical, aplhabetical (order of items) and by date
Why transition metals possess abnormal configuration?
It is not an abnormal configuration. For example let us consider the first series of transition elements in the fourth period. They are filling the 3d subshell. According to Aufbau Theorem, the electrons fill in such a way in the order of the increasing energy, (not in the order of the principal energy levels). 4s has a lesser energy than 3d, therefore the latter fills later.
How do I fill out a money order a claim card show me?
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Are lines and arrows used to inicate electron configuration?
Yes, lines and arrows can be used to indicate electron configuration. Arrows are usually used to represent electrons, while lines can be used to show the energy levels of electrons or the order in which they fill orbitals.
What is the orbital of the element yttrium?
The valence electrons fill in 4d orbital The electron configuration of yttrium is [Kr]4d15s2.
What is the number of electrons to fill the outer shell of nitrogen?
As Nitrogen (N) have atomic number 7, and electronic configuration is 2,5. therefore N required 3 elecrons to complete their outermost shell or orbital.
