Complete the table by giving the values of X, Y, and Z. Elements A and B are involved in bonding. Give the formula of the compound formed.

The mass number is the sum of protons and neutrons.

The value of X is $\boxed{\text{18}}$.

For a neutral atom, the number of electrons is equal to the number of protons.

The value of Y is $\boxed{\text{17}}$.

The mass number is the sum of protons and neutrons.

The value of Z is $\boxed{\text{7}}$.

Element A has 17 protons and 17 electrons (electronic configuration 2, 8, 7). It tends to gain 1 electron to form an ion with a charge of $1-$.
Element B has 12 protons and 12 electrons (electronic configuration 2, 8, 2). It tends to lose 2 electrons to form an ion with a charge of $2+$.

To balance the charges, two A ions ($1-$ each) are needed for every one B ion ($2+$).
The formula of the compound formed is $\boxed{\text{BA}_2}$.

Element A has an atomic number of 17.
The electronic configuration is $\boxed{\text{2, 8, 7}}$.

Element D has an atomic number of 8.
The electronic configuration is $\boxed{\text{2, 6}}$.

Element C has an atomic number of 3 (electronic configuration 2, 1). It has 1 valence electron.
Element C falls in $\boxed{\text{Group 1}}$.

Element D has an atomic number of 8 (electronic configuration 2, 6). It has 6 valence electrons.
Element D falls in $\boxed{\text{Group 16 (or Group VI)}}$.