1. Predicting chemical reactions…

2. Atoms react to get the right amount of valence electrons
Sodium loses one electron to chlorine
Na loses one
Cl gains one
Afterward they both have 8 ve-
They stick together because of their opposite charges
Formula: NaCl

3. Transferring Multiple Electrons
More than one electron can be transferred
Mg has 2 ve-
O has 6 ve-
Mg transfers both electrons so that both have 8 ve-
Formula: MgO

4. Transferring multiple electrons
Both electrons do not have to be transferred to the same atom
Mg has 2 ve-
Cl has 7 ve-
Mg transfers 1 each to 2 different Cl atoms
Formula: MgCl2
“2” subscript shows 2 atoms of Cl are present

5. Try it! Predict the product these two atoms will make:
Which atom will lose? Which atom will gain?
How many of each atom are needed to have full valence shells?
Write the formula.

6. Try it! Answer Lithium loses 1 electron Oxygen gains 2 electrons
2 lithium atoms are needed for every 1 oxygen atom
Formula: Li2O

7. Practice
For each of these practice problems, give the formula of the compound they will make, and say how many electrons total are transferred.
K (1 ve) + F (7 ve) = _____________, ________ electrons are transferred
Be (2 ve) + Cl (7 ve) = _____________, ________ electrons are transferred
Li (1 ve) + N (5 ve) = _____________, ________ electrons are transferred
Al (3 ve) + P (5 ve) = _____________, ________ electrons are transferred

8. Practice Answers
For each of these practice problems, give the formula of the compound they will make, and say how many electrons total are transferred.
K (1 ve) + F (7 ve) = KF, 1 electrons are transferred
Be (2 ve) + Cl (7 ve) = BeCl2, 2 electrons are transferred
Li (1 ve) + N (5 ve) = Li3N, 3 electrons are transferred
Al (3 ve) + P (5 ve) = AlP, 3 electrons are transferred

9. Practice Part 2
For each of these practice problems, give the formula of the compound they will make, and say how many electrons total are transferred.
Ca (2 ve) + S (6 ve) = _____________, ________ electrons are transferred
Zn (1 ve) + N (3 ve) = _____________, ________ electrons are transferred
Al (3 ve) + Br (7 ve) = _____________, ________ electrons are transferred
Al (3 ve) + O (6 ve) = _____________, ________ electrons are transferred

10. Practice Part 2 Answers
For each of these practice problems, give the formula of the compound they will make, and say how many electrons total are transferred.
Ca (2 ve) + S (6 ve) = CaS, 2 electrons are transferred
Zn (1 ve) + N (3 ve) = Zn3N, 3 electrons are transferred
Al (3 ve) + Br (7 ve) = AlBr3, 3 electrons are transferred
Al (3 ve) + O (6 ve) = Al2O3, 6 electrons are transferred