Which of the following represents an ion? a 4he b na 2+ c ca d mg

Na2+(answer  B)  represent ions.

This is because it has a charge of 2+. ion is formed when an  atom gain or lose  electrons.  when an atom lose electrons it form ion which is positively  charged . On the other hand when atom gain electrons it forms ion of negatively charged. Na2+  has a charge of 2+ since it loses two electrons.

cytokinesis is the splitting of a cell membrane to form 2 identical daughter cells. it's similar to mitosis as both cells have identical copies of dna and cytokinesis is a step in the mitotic cycle.

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.