Question

identify the charge of the ions in each compound, then type the formula below:
li?
n?
lithium nitride
(type final formula)
be?
br?
beryllium bromide
(type final formula)
answer key

Explanation:

Step1: Determine the charge of Li

Li is in group 1 of the periodic table. Elements in group 1 lose 1 electron to form cations. So, the charge of Li is $1+$.

Step2: Determine the charge of N

N is in group 15 of the periodic table. Elements in group 15 gain 3 electrons to form anions. So, the charge of N is $3-$.

Step3: Write the formula of lithium nitride

Using the criss - cross method (swap the absolute values of the charges as subscripts). For $Li^{1+}$ and $N^{3 -}$, the formula is $Li_3N$.

Step4: Determine the charge of Be

Be is in group 2 of the periodic table. Elements in group 2 lose 2 electrons to form cations. So, the charge of Be is $2+$.

Step5: Determine the charge of Br

Br is in group 17 of the periodic table. Elements in group 17 gain 1 electron to form anions. So, the charge of Br is $1-$.

Step6: Write the formula of beryllium bromide

Using the criss - cross method (swap the absolute values of the charges as subscripts). For $Be^{2+}$ and $Br^{1 -}$, the formula is $BeBr_2$.

Answer:

Li: $1+$, N: $3-$, formula of lithium nitride: $Li_3N$; Be: $2+$, Br: $1-$, formula of beryllium bromide: $BeBr_2$