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

It contains most of the mass of the atom.

Explanation:

An atom is smallest unit of a matter or substance.It consist of three subatomic particles : electrons, protons, neutrons.

Protons and neutrons are located in the center of an atom called as nucleus where mass of an atom is concentrated.

Atomic mass = Number of protons + Number of neutrons

Electrons are located outside the nucleus where they orbit in different energy levels around the nucleus.  they have negligible mass as compared to protons and neutrons.

Thus the true statement concerning the atomic nucleus is It contains most of the mass of the atom.

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explanation:

covalent bonds

consist of pairs of electrons shared by two atoms, and bind the atoms to fixed orientation and requre high energies to break them

ionic bonds

when two atoms differ considerably in their electronegativity, then one of the atoms will lose its electron to the other atom. this results in a positively charged ion(cation) and a negatively charged ion (anion)

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.