Question

most of an atoms mass is found in protons and neutrons.
a neutron has a positive electrical charge.
the nucleus of an atom contains at least one proton.
the nucleus of an atom is found in the atoms center.

Explanation:

• Most of an atom's mass is found in protons and neutrons: Protons and neutrons are located in the nucleus. They have much greater mass compared to electrons (which are outside the nucleus). Electrons have negligible mass in comparison. So, the majority of an atom's mass comes from protons and neutrons.
• The nucleus of an atom is found in the atom's center: The atomic model (such as the Rutherford model) shows that the nucleus is a dense, positively - charged core located at the center of the atom.
• The nucleus of an atom contains at least one proton: By definition, the nucleus must have at least one proton. For example, hydrogen (the simplest atom) has a nucleus with one proton.
• A neutron has a positive electrical charge: This is incorrect. A neutron has a neutral charge. A proton has a positive charge, and an electron has a negative charge.

Answer:

• Most of an atom's mass is found in protons and neutrons.
• The nucleus of an atom is found in the atom's center.
• The nucleus of an atom contains at least one proton.