Chemistry, 23.08.2019 05:00 aliviadushane

Aspecific amount of energy is emitted when excited electrons in an atom in a sample of an element return to the ground state. this emitted energy can be used to determine the
a) mass of the sample
b) volume of the sample
c) identity of the element
d) number of moles of the element

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Answer from: chancler

The answer is C. The specific amount of energy emitted when electrons jump from excited states to the ground state refers to emission spectrum. The energy is emitted in the form of photons, and the photons have very specific wavelengths (energy) that correspond to the energy gaps between the excited states and the ground state. The specific wavelengths of light emitted are referred to as the "emission spectrum," and each element produces a different emission spectrum. Thus, this emitted energy can be used to identify the element from which your sample was taken.

Answer from: Quest

answer is a

explanation:

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.

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