Chemistry, 17.07.2019 22:30, quynhnguyen7454

Given that mh = 1.007825 u, is the mass of a hydrogen atom 1h greater than, less than, or equal to 1/12 the mass of a 12c atom? select the correct answer and explanation.

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answered: greeneashlynt

Question is incomplete. Complete question is

Given that mH = 1.007825 u, is the mass of a hydrogen atom 1H greater than, less than, or equal to 1/12 the mass of a 12C atom? Select the correct answer.

A: 1/12 of the mass of a 12C atom is less than 1 u. Therefore, the mass of the hydrogen atom is less than 1/12 of the mass of a 12C atom.

B: 1/12 of the mass of a 12C atom is exactly 1 u. Therefore, the mass of the hydrogen atom is less than 1/12 of the mass of a 12C atom.

C: 1/12 of the mass of a 12C atom is exactly 1 u. Therefore, the mass of the hydrogen atom is greater than 1/12 of the mass of a 12C atom.

D: 1/12 of the mass of a 12C atom is greater than 1 u. Therefore, the mass of the hydrogen atom is greater than 1/12 of the mass of a 12C atom.

E: 1/12 of the mass of a 12C atom is exactly 1 u. Therefore, the mass of the hydrogen atom is equal to 1/12 of the mass of a 12C atom.

Correct option C i.e. 1/12 of the mass of a 12C atom is exactly 1 u. Therefore, the mass of the hydrogen atom is greater than 1/12 of the mass of a 12C atom.

Reason:

Carbon-12 has 6 protons, 6 neutrons and 6 electrons, while hydrogen has 1 proton and 1 electron. Due to this, 1/12 of the mass of a 12-C atom is exactly 1 u. and the mass of the hydrogen atom is greater than 1/12 of the mass of a 12-C atom.

answered: Guest

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answered: Guest

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.