Chemistry, 23.01.2020 11:31 whityelaine812

Why pluto is removed from planet?

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Answer from: hjgjlgkjg

Pluto was ruled not a planet anymore because it is a "dwarf planet"

Apparently, the International Astronomical Union's (IAU) definition of a planet includes that a planet should be part of a body that would orbit the sun.

According to the IAU, there are three criteria's that contribute to a planet being called a planet.

1. It is within orbit around the Sun.

2. It has a sufficient mass to assume a nearly round shape

and 3. It has "cleared the neighborhood" around it's orbit.

Pluto only so happens to meet 2 of these requirements, not including the third option.

Answer from: izzyisawesome5232

In august 2006 the international astronomical union (IAU) downgraded the status of Pluto to that of "Dwarf planet." this means that from now on only the rocky worlds of the inner solar system and the gas giants of the outer system will be designated.

("Hope this is helpful.")

Answer from: Quest

assuming that your periodic table has eighteen columns, you should highlight the four elements in the third column from the left of the table.

explanation

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.