2.18 determine whether each of the following statements is
true or false; if false, correct the statement to make it
true: (a) the nucleus has most of the mass and compris-
es most of the volume of an atom; (b) every atom of a
given element has the same number of protons; (c) the
number of electrons in an atom equals the number of
neutrons in the atom; (d) the protons in the nucleus of
the helium atom are held together by a force called the
strong nuclear force.

(a) The nucleus has most of the mass and comprises most of the volume of an atom;  false

The nucleus has most of the mass but the volume of an atom is depends on the distance between the nucleus and the position of the electrons.

(b) Every atom of a  given element has the same number of protons;  true

They may have different number of neutrons and so you have isotopes but the number of protons remain the same for a given element.  

(c) The  number of electrons in an atom equals the number of  neutrons in the atom; false

The  number of electrons in an atom equals the number of  protons in the atom.

The electrons are negatively charged which compensate the positively charged protons not the neutrons which do not have a charge (they are neutral).

(d) The protons in the nucleus of  the helium atom are held together by a force called the  strong nuclear force. true

these nuts

why is arctic sea ice important? arctic sea ice keeps the polar regions cool and moderate global climate. sea ice has a bright surface; 80 percent of the sunlight that strikes it is reflected back into space. as sea ice melts in the summer, it exposes the dark ocean surface.