)the atomic radius of main-group elements generally increases down a group because a. effective nuclear charge increases down a group b. effective nuclear charge decreases down a group c. effective nuclear charge zigzags down a group d. the principal quantum number of the valence orbitals increases e. both effective nuclear charge increases down a group and the principal quantum number of the valence orbitals increases

Hey! The answer should be D.

indium, and thallium have three electrons i think

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.