A scientist dissolved a white powder in water and noted that the resulting solution was acidic. Why should the scientist not infer that the white powder contained hydrogen ions? (2 points) Acids never contain hydrogen ions. Bases always contain hydrogen ions. Some acids do not contain hydrogen ions. Acids only contain hydroxyl ions.

Some acids do not contain hydrogen

Explanation:

[prime examples are Lewis Acids]

There are 3 definitions of acid and bases. Arrhenius, bronsted and lewis acid bases. Among those Lewis acid are tricky because for them Some acids do not contain hydrogen. It's defintion of acid is something that accepts electrons (doesn't necessarily have to have hydrogen ions).

For example, From the Lewis theory, one can see that it is not necessary for an acid to have any protons, strictly speaking. The boron halides BF3, BCl3, BBr3, and BI3 are all Lewis acids and do not contain hydrogen. AlCl3 and AlBr3 are also common Lewis Acids used in Friedel-Crafts chemistry and do not contain hydrogen.

Finally, if we look at AlCl3 in waterFrom the reaction AlCl3 + 3H2O <=> Al(OH)3 + 3HCl,

HCl is a strong acid, so it will dissociate in water to form H+ and Cl-. As a result of this reaction, the solution will be acidic, with a pH < 7.

Therefore, the scientist cannot infer that white powder contained hydrogen atoms. It was the powder that reacted with water that led to formation of hydrogen ions, it wasn't necessarily present. Some common acids that have hydrogen ions are HCl, H2SO4 and such.

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.

it is the most commonly accepted one