Final answer:
Sodium and lithium form ions with a 1+ charge due to the loss of one electron to achieve a noble gas electron configuration, resulting in a 1+ cation.
Step-by-step explanation:
Sodium and lithium form ions with a 1+ charge because of the loss of one electron. In their neutral state, sodium and lithium have an equal number of protons and electrons. By losing one electron, these elements achieve a noble gas electron configuration, which results in a positively charged ion, or cation. Sodium, for example, loses one electron and ends up with 11 protons and 10 electrons, resulting in a Na+ ion. This is because metals in Group 1A of the periodic table, which includes sodium and lithium, characteristically lose one electron to form 1+ ions.