Question

a. use the periodic table to write the formula (including the charge) for the simple ion formed by the element with atomic number 17.
b. use the periodic table to write the formula (including the charge) for the simple ion formed by the element with atomic number 34.
c. use the periodic table to write the formula (including the charge) for the simple ion formed by the element with atomic number 15.

Explanation:

Step1: Identify element for atomic number 17

The element with atomic number 17 is chlorine (Cl). Chlorine is in group 17 (halogens) and gains 1 electron to form an ion.

Step2: Write ion formula for Cl

When chlorine gains 1 electron, it forms a chloride ion with a - 1 charge. The formula is $Cl^{-}$.

Step3: Identify element for atomic number 34

The element with atomic number 34 is selenium (Se). Selenium is in group 16 and gains 2 electrons to form an ion.

Step4: Write ion formula for Se

When selenium gains 2 electrons, it forms a selenide ion with a - 2 charge. The formula is $Se^{2 - }$.

Step5: Identify element for atomic number 15

The element with atomic number 15 is phosphorus (P). Phosphorus is in group 15 and gains 3 electrons to form an ion.

Step6: Write ion formula for P

When phosphorus gains 3 electrons, it forms a phosphide ion with a - 3 charge. The formula is $P^{3 - }$.

Answer:

a. $Cl^{-}$
b. $Se^{2 - }$
c. $P^{3 - }$