Question

the united nations declared the year 2019 as the year of the periodic table. the year 2019 marks 150 years since the discovery of the periodic system of the arrangement of elements which led to the periodic table, mostly credited to dmitri mendeleev. since 1869, scientists have discovered or synthesized a number of new elements which exhibit properties in keeping with the logic of the the fact that the four new elements are period 7 of the table means that they all: a. have 7 shells of electrons b. have 7 valence electrons c. form ions with charges of 7+ d. have an effective nuclear charge of 7+

Explanation:

Elements in Period 7 of the periodic table have 7 electron - shells. The periodic table arranges elements based on the number of electron - shells (periods) and valence electrons (groups). Period number corresponds to the number of electron shells an element's atoms have.

Answer:

A. have 7 shells of electrons