Answer
(a) $5$
(b) $11$
(c) $4$
(d) $44$
Work Step by Step
When we count the number of atoms in a formula unit, an element with no subscript means there is one atom of that element in that compound, and subscripts tell us how many atoms of a particular element in a compound. When a group of elements are enclosed in parentheses and followed by a subscript, that means the subscript pertains to all of the elements inside the parentheses.
(a) There are two indium atoms and three oxygen atoms in this compound for a total of $5$ atoms in one formula unit.
(b) There is one cerium atom, two sulfur atoms, and eight oxygen atoms in this compound for a total of $11$ atoms in one formula unit.
(c) There is one thallium atom and three fluorine atoms in this compound for a total of $4$ atoms in one formula unit.
(d) There are 10 calcium atoms, six phosphorus atoms, and 26 oxygen atoms, and two hydrogen atoms in this compound for a total of $44$ atoms in one formula unit.
