Binary Ionic Compounds CU

Sodium is a metal in the first column of the periodic table. What ion will it form?

• Na+

• Na-

• Na2+

• Na2-

Answer explanation

Because sodium (Na) is in the first column, we know it has one valence electron. Because elements want to have a full valence electron shell, Na will lose it's one valence electron. Because it is losing a negative, it will beocme positive. And because it's just one valence electron, the charge is only 1.

Think 0 minus negative one is the same as 0 - - 1 which is the same as 0 +1.

How many sodium ions are in this compound?

• 1

• 2

• 3

• 0

Answer explanation

A small subscript 2 means there are 2 of the element that it is attached to.

Tags

NGSS.MS-PS1-1

Because Sodium has a 1+ charge (Na+) which ion would it bond with in a 1:1 ratio?

• Na+

• Mg2+

• S2-

• Cl-

Answer explanation

Ions want to bond to make their compound neutral. To do this, they bond in ways that cancel out their charges and make them 0. So, if you have a +1 ion, like in this question it will want to bond with a -1 ion. Because +1 plus -1 equals 0. (1-1=0)

A magnsium (Mg) ion has a 2+ charge. Which of these would we expect it to bond to? (there are 2 correct answers)

• 2Cl-

• S2-

• Be2+

• 2Na+

Answer explanation

Because the magnesium ion has a positive 2 charge, it needs 2 negative charges to reach a neutral (0) charge. There are two ways this can be achieved.

The first way is for it to bond to an ion with a negative 2 charge, like Sulfide (S2-)

+2 -2 = 0

The second way is for it to bond with TWO ions that each have a negative 1 charge, like 2Cl- ions.

+2 -1 -1 = 0

Which of these ionic compounds would actually occur?

• NaO

  (Na+ and O2-)

• BeMg

  (Be2+ and Mg2+)

• SO

  (S2- and O2-)

• LiF

  (Li+ and F1)

Answer explanation

Remember the charges need to equal zero. Each of the other options has like forces- a positive and a positive or a negative and a negative. Only Lif and NaO have a positive and a negative force. However NaO would not occur because Na has a +1 charge and O has a -2 charge. +1 - 2 = -1 not zero, which is why LiF is the answer. Because Li+ and F- cancel eachother out and create a neutral compound.

+1-1 = 0

Tags

NGSS.HS-PS1-3

How confident are you in your ability to find the formula when I give you the ions and their charges?

(For example: If i give you Li+ and O2-; how confident are you that you could find the formula?)

• 1= not at all

• 2= I might guess correctly

• 3= I could with help

• 4= I think I can

• 5= I know I can do it myself

After today's pratice worksheet:

What is one thing you're still confused about or one question you have about what we did today?