The true statement concerning the atomic nucleus is:
It contains protons, neutrons, and electrons.
It takes up most of the volume of the atom.
It contains most of the mass of the atom.
It is made up of electrons only.
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1. It contains protons,neutrons and electrons which is a true statement for atomic nucleus.

We can also determine number of valence electrons through atomic number by its electronic configuration. (K,L,M Shells)

Explanation:

passing a magnet thought the

mixture , because iron gets attracted to magnet .

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current