# Why Is 3rd Shell 8 Or 18?

## Why does scandium have 9 electrons in the third shell?

Scandium is the first element of the period table where electron configurations start getting a little wild.

Every element adds one more electron to the outermost shell.

Instead of having three electrons in the outer shell, scandium adds its electron to the second to last shell.

The electron configuration is 2-8-9-2..

## Does the third shell have 8 or 18 electrons?

Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.

## Why can the third energy level hold 18 electrons?

Electrons in this orbital are called s electrons and have the lowest energy of any electrons in that principal energy level. … The five d orbitals can hold up to 10 electrons. Thus, the third level holds a maximum of 18 electrons: 2 in the s orbital, 6 in the three p orbitals, and 10 in the five d orbitals.

## How many electrons are on the 3rd shell?

eight electronsThe second shell can hold a maximum of eight electrons. When this is filled, electrons go into the third shell, which also holds a maximum of eight electrons.

## Why are shells named KLMN?

The names of the electron shells come from a fellow named Charles G. Barkla, a spectroscopist who studied the X-rays that are emitted by atoms when they are hit with high energy electrons. … This innermost shell is now called the K-shell, after the label used for the X-ray.

## What is the highest occupied energy level?

What is it meant by the highest occupied energy level in an atom? The highest occupied energy level in an atom is the electron-containing main energy level with the highest number.

## Why does the fourth period have 18 elements?

Classification of Elements and Periodicity in Properties. Account for the fact that the 4th period has eighteen and not eight elements. Therefore, 18 elements (not eight) are present in the 4th period. The 4d and 4f sublevels are higher in enthalpy than 5s and hence are filled up in the next periods.

## Can two electrons be in the same shell?

The state of a system is completely described by a complete set of quantum numbers. … The Pauli exclusion principle says that no two electrons can have the same set of quantum numbers; that is, no two electrons can be in the same state. This exclusion limits the number of electrons in atomic shells and subshells.

## Why does the third period contain 8 elements but not 18?

The electron capacity of third shell is 18. So the third period should actually contain 18 elements. But it contains only 8 elements due to the law of electron octet. … This is because of the fact that electrons are filled in these shells in the increasing order of electrons.

## Why outermost shell Cannot have more than 8 electrons?

The shells of an atom cannot accommodate more than 8 electrons, even if it has a capacity to accommodate more electrons. This is a very important rule called the Octet rule. According to this rule, atoms gain, loose or share electrons to achieve the stable configuration similar to the nearest noble gas.

## Why can sulfur have more than 8 electrons?

Its structure is Here the sulfur atom has six electron pairs in its valence shell. An atom like phosphorus or sulfur which has more than an octet is said to have expanded its valence shell. This can only occur when the valence shell has enough orbitals to accommodate the extra electrons. … An octet would be 3s23p6.

## Can fluorine have more than 8 electrons?

Each fluorine atom has an octet, but the sulfur atom has 12 electrons surrounding it rather than 8.

## Why there are only 8 electrons in the third shell?

The third shell of an atom has 18 electrons only not 8 electrons. You might be confused because first the electrons of 4s are filled and then the 10 electrons of 3d shells are filled. They are filled because of the n-l rule. … So after filling the 3s and 3p subshell with 8 electrons, the next shell to fill is the 4s one.

## Can there be more than 8 electrons in a shell?

octet rule: Atoms lose, gain, or share electrons in order to have a full valence shell of eight electrons. Hydrogen is an exception because it can hold a maximum of two electrons in its valence level.