As you pass a magnet over a blackish-yellow powder on a glass plate, black particles separate from the powder and become attached to the magnet. after a few passes of the magnet over the powder nothing but a yellow powder remains in the glass plate. the original blackish-yellow powder was:

AS given that we have started with a solid powder on a glass plate which appears to be blackish yellow, on passing magnet the black particles separated.

so the black particles are magentic in nature. however the yellow portion of powder is not magnetic or diamagnetic

so its clear that we are able to separate the black and yellow portions by simple physical methods.

If we are able to separate any two substances by simple physical methods then it means that the powder is a mixture and not a compount

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.

they vary. it used to be meat, grain, bread, candy, beverages, donuts, and fruits/vegetables. now they added exercise in.