17) the elements sodium, magnesium, and silicon
a) are isotopes of each other
b) are in the same period of elements

A period is a horizontal row and therefore these elements are all in the same period.

If you pull up an image of the periodic table, you will see that all of them are in the same row.

They are not isotopes of each other because an isotope is the same element with a different number of neutrons (example: carbon-12, carbon-13).

Hopefully I helped :)

B) are in the same period of elements.

Explanation:

The elements sodium, magnesium, and silicon

A) are isotopes of each other . NO. Isotopes are 2 or more forms of the same element, with a different number of neutrons.

B) are in the same period of elements. YES.

Let's consider the electron configuration of these elements.

₁₁Na 1s² 2s² 2p⁶ 3s¹

₁₂Mg 1s² 2s² 2p⁶ 3s²

₁₄Si 1s² 2s² 2p⁶ 3s² 3p²

Since the valence electrons are in the level 3, they all belong to the third period in the periodic table.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.