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Spectrum A
Spectrum B
7
100
80
100
80
60
40
2011
60
40
20
0
Which of the spectra shown could represent the isotopic composition of an
unknown element that has an average atomic mass of 25.5 amu?
0
22 23 24 25 26 27
22 23 24 25 26 27
A Spectrum A
Relative Abundance (%) Relative Abundance (%)
Atomic Mass (amu)
Relative Abundance (%) Relative Abundance (%)
Atomic Mass (amu)
Spectrum C
100-
80
® Spectrum B
60
Spectrum D
100
80
60
40
20
01
22 23 24 25 26 27
© Spectrum C
40
20
0
II
22 23 24 25 26 27
D Spectrum D
Atomic Mass (amu)
Atomic Mass (amu)

where's the diagram?

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

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 have energy higher than those in the orbital while lower than those of the orbital.

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

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration 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 and should be highlighted as well.

i'm pretty sure it is letter c.) car

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72