Calcium And Iodine Ionic Compound, Calcium Forms Ions With A Charge Of +2

Cjonathanlewisforcongress.com

assignments –unit 3 part 5

chemical formulas

ionic compounds

covalent compounds

Students with computers – take notes and do practices for each section

Students without computers – take notes and do review questions in each section

Chemical Formula

The use of chemical symbols and subscripts to represent elements in a compound.

You are watching: Calcium and iodine ionic compound

· Define chemical formula.

· Explain how to write a chemical formula.

· Identify the ratio of differentelementsin a compound from its chemical formula.

You can make a simple salad dressing using just the two ingredients pictured above: oil and vinegar. Recipes for oil-and-vinegar salad dressing vary, but they typically include about three parts oil to one part vinegar, or a ratio of 3:1. For example, if you wanted to make a cup of salad dressing, you could mix togethercup of oil andcup of vinegar. Chemicalcompoundsalso have “ingredients” in a certain ratio. However, unlike oil-and-vinegar salad dressing, a chemical compound always has exactly the same ratio ofelements. This ratio can be represented by a chemical formula.

RepresentingCompounds

In achemical formula, theelementsin a compound are represented by their chemical symbols, and the ratio of different elements is represented by subscripts. Consider the compoundwateras an example. Each water molecule contains two hydrogenatomsand one oxygen atom. Therefore, the chemical formula for water is:

H2O

The subscript 2 after the H shows that there are twoatomsof hydrogen in the molecule. The O for oxygen has no subscript. When there is just one atom of an element in a molecule, no subscript is used in the chemical formula.

Formulas for Ionic and CovalentCompounds

TheTablebelowshows four examples of compounds and their chemical formulas. The first two compounds are ionic compounds, and the second two are covalent compounds. Each formula shows the ratio ofionsoratomsthat make up the compound.

Name of Compound

Type of Compound

Ratio ofIonsor Atoms of Each Element

Chemical Formulas

There is a different rule for writing the chemical formula for each type of compound.

Ionic compounds are compounds in which positive metal ions and negative nonmetal ions are joined by ionic bonds. In these compounds, the chemical symbol for the positive metal ion is written first, followed by the symbol for the negative nonmetal ion. The video at the following URL gives a fuller explanation of ionic compounds and their formulas:http://www.youtube.com/watch?v=vscoYh6m46M.

· Q:The ionic compound lithium fluoride consists of a ratio of one lithium ion (Li+) to one fluoride ion (F-). What is the chemical formula for this compound?

· A:The chemical formula is LiF.

Covalent compounds are compounds in whichnonmetalsare joined by covalent bonds. In these compounds, the element that is farther to the left in the periodic table is written first, followed by the element that is farther to the right. If both elements are in the same group of the periodic table, the one with the higher period number is written first. The following URL gives a fuller explanation of covalent compounds and their formulas:http://www.youtube.com/watch?v=ZTMHbKtgI-M.

· Q:A molecule of the covalent compound nitrogen dioxide consists of one nitrogen atom (N) and two oxygen atoms (O). What is the chemical formula for this compound?

· A:The chemical formula is NO2.

Summary

· Compounds are represented by chemical formulas. Elements in a compound are represented by chemical symbols, and the ratio of different elements is represented by subscripts.

See more: Antelope Canyon Tours 22 S Lake Powell Blvd Page, Az 86040, Antelope Canyon Tours

· There are different rules for writing the chemical formulas for ionic and covalent compounds.

Explore More

At the following URL, do the online learning activity on chemical formulas. Then take the quiz at the end of the activity to check your comprehension.

http://www.wisc-online.com/Objects/ViewObject.aspx?ID=GCH603

Review

1. Complete the following analogy: A chemical symbol is to an element as a chemical formula is to a(n) __________.

2. The compound sodium sulfide consists of a ratio of one sodium ion (Na+) to two sulfide ions (S2-). Write the chemical formula for this compound.

3. A molecule of sulfur dioxide consists of one sulfur atom (S) and two oxygen atoms (O). What is the chemical formula for this compound?

4. Identify the ratio of atoms in the compound represented by the following chemical formula: N2O5.

Ionic Compounds

Compounds in which electrons are transferred from one atom to another.

· Describe ioniccompoundsand how they form.

· Explain how ioniccompoundsare named.

· Identify properties and uses of ioniccompounds.

The truck pictured above is spreading crystals of the salt calcium chloride on a snowy road to prevent ice from forming. The crystals lower thefreezingpoint ofwaterso when the snow melts, it won’t turn to ice. Do you know why calcium chloride lowers the freezing point of water? The answer has to do with the type of compound that calcium chloride is. Calcium chloride is an ionic compound.

What Are Ionic Compounds?

All compounds form whenatomsof differentelementsshare or transferelectrons. Compounds in which electrons are transferred from one atom to another are called ioniccompounds. In this type of compound,electronsactually move between theatoms, rather than being shared between them. When atoms give up or accept electrons in this way, they become charged particles calledions. The ions are held together by ionic bonds, which form an ionic compound. Ionic compounds generally form betweenelementsthat aremetalsand elements that are nonmetals. For example, the metal calcium (Ca) and the nonmetal chlorine (Cl) form the ionic compound calcium chloride (CaCl2). In this compound, there are two negative chlorideionsfor each positive calcium ion. Because the positive and negative charges cancel out, an ionic compound is neutral in charge.

Q:Now can you explain why calcium chloride prevents ice from forming on a snowy road?

A:If calcium chloride dissolves inwater, it breaks down into itsions(Ca2+and Cl-). Whenwaterhas ions dissolved in it, it has a lowerfreezingpoint. Pure water freezes at 0°C. With calcium and chloride ions dissolved in it, it won’t freeze unless thetemperaturereaches -29°C or lower.

See more: How Many Tattoos Does Donnie Wahlberg Have, How Many Tattoos Does Donnie Wahlberg Tattoos

Crystals

Many compounds form molecules, but ionic compounds form crystals instead. Acrystalconsists of many alternating positive and negative ions bonded together in a matrix. Look at the crystal of sodium chloride (NaCl) in theFigurebelow. The sodium and chloride ions are attracted to each other because they are oppositely charged, so they form ionic bonds.