SIM for 3rd year by Beatriz R. Rubico

OBJECTIVES:

1. Define the meaning of atom.

2. Show how the electrons configuration of an atom is related to its tendency to give up or gain electrons.

3. Solve simple problems on percentage composition.

4. Compute the molecular formula from the percentage composition and empirical formula.

INTRODUCTION:

Have you ever imagined how the circulation of your lifehappens to be fascinating and so splendid?

Think about it……..

Your world is coated with the fruit of chemistry and sparkledwith the process of science which plays a vital role in this society. However, many have long ignored it.

Everything in the universe made of atoms. An atom is the basic chemical unit of matter that makes up a molecule. An atom is composed of a positively charged nucleus made of protons and neutrons surrounded by negatively charged electrons

When atoms become connected or bonded with other atoms, they form molecules. Molecules can be as simple as a molecule of hydrogen gas which is made of nothing but two hydrogen atoms. Molecules can also be made of thousands of atoms of many different elements.

GUIDE CARD:

Suppose you could divide an element into two pieces.

Then you continued to divide each piece into smaller and

smaller pieces. Finally, you would not be able to divide a piece

and still have pieces of the same element. All elements are

composed of atoms.

Colors emitted by heating an element are very useful in

identifying such an element, the study of the colors emitted by

the atom led to an understanding of the nature of the atoms.

What gives the color?

Match the Column A with Column B

Column A

1. Antimony2. Strontium salt3. Barium salt4. Sodium salt5. A mixture of copper salts and Mercury chloride

Column B

A. BlueB. White flameC. RedD.GreenE. Yellow

ACTIVITY CARD NO. 1

What you need to know...…

Silicon Electron Configuration Example

Question:

Determine the electron configuration of silicon.

Solution:

Silicon is element 14. It has 14 protons and 14 electrons. The lowest energy level of an atom is filled first. The arrows in the graphic show the s quantum numbers, spin 'up' and spin 'down'.

Step A shows the first two electrons filling the 1s orbital and leaving 12 electrons.

Step B shows the next two electrons filling the 2s orbital leaving 10 electrons.

The 2p orbital is the next available energy level and can hold six electrons. Step C shows these six electrons and leaves us with four electrons.

Step D fills the next lowest energy level, 3s with two electrons.

Step E shows the remaining two electrons starting to fill the 3p orbital. Remember one of the rules of the aufbau principle is that the orbital’s are filled by one type of spin before the opposite spin starts to appear. In this case, the two spin up electrons are placed in the first two empty slots, but the actual order is arbitrary. It could have been the second and third slot or the first and third.

Answer

The electron configuration of silicon is 1s22s2p63s23p2.

Based on the examples given, write the electronic configuration of the following

elements.

1. Phosphorus = 152. Magnesium = 123. Manganese = 254. Potassium= 195. Iron= 26

Did you get all correctly? If yes, very good. If not, try to review your answer before you go to the next activity

ACTIVITY CARD NO. 2

What you need to know…..

Mass Percent Composition Problem

Calculation of Mass Percent Composition

This is a worked example problem showing how to calculate mass percent composition.

Problem

Bicarbonate of soda (sodium hydrogen carbonate) is used in many commercial preparations. Its formula is NaHCO3. Find the mass percentages (mass %) of Na, H, C, and O in sodium hydrogen carbonate.

Solution

First, look up the atomic masses for the elements from the Periodic Table. The atomic masses are found to be:

Na is 22.99H is 1.01C is 12.01O is 16.00

Next, determine how many grams of each element are present in one mole of NaHCO3:

22.99 g (1 mol) of Na1.01 g (1 mol) of H12.01 g (1 mol) of C48.00 g (3 mole x 16.00 gram per mole) of O

The mass of one mole of NaHCO3 is:

22.99 g + 1.01 g + 12.01 g + 48.00 g = 84.01 g

And the mass percentages of the elements are

mass % Na = 22.99 g / 84.01 g x 100 = 27.36 %mass % H = 1.01 g / 84.01 g x 100 = 1.20 %mass % C = 12.01 g / 84.01 g x 100 = 14.30 %mass % O = 48.00 g / 84.01 g x 100 = 57.14 %

Answer

mass % Na = 27.36 %mass % H = 1.20 %mass % C = 14.30 %mass % O = 57.14 %

When doing mass percent calculations, it is always a good idea to check to make sure your mass percents add up to 100%.

27.36 + 14.30 + 1.20 + 57.14 = 100.00

Based from the given example, try to determine the percentage composition of the following compounds.

1. What is the percentage composition of Calcium carbonate, CaCO3?

2. What is the percentage composition of Alcohol, C2H5OH?3. What is the percentage composition of di-ethyl oxide, (C2H5)2O?4. What is the percentage composition of acetic acid, HC3COOH?5. What is the percentage composition of hydrated magnesium

silicate, H4Mg3Si2O+9?

Did you get all the answer correctly? If yes, you did a great job.

ACTIVITY NO. 3

What you need to know…..

Finding the Empirical Formula from Percent Composition Data

Steps for Finding the Empirical Formula

You can find the empirical formula of a compound using percent composition data. If you know the total molar mass of the compound, the molecular formula usually can be determined as well. The easiest way to find the formula is:

1. Assume you have 100 g of the substance (makes the math easier because everything is a straight percent).

2. Consider the amounts you are given as being in units of grams. 3. Convert the grams to moles for each element. 4. Find the smallest whole number ratio of moles for each element.

Empirical Formula Problem

Find the empirical formula for a compound consisting of 63% Mn and 37% O

Solution for Finding the Empirical Formula

Assuming 100 g of the compound, there would be 63 g Mn and 37 g OLook up the number of grams per mole for each element using the Periodic Table.

There are 54.94 grams in each mole of manganese and 16.00 grams in a mole of oxygen.63 g Mn × (1 mol Mn)/(54.94 g Mn) = 1.1 mol Mn37 g O × (1 mol O)/(16.00 g O) = 2.3 mol O

Find the smallest whole number ratio by dividing the number of moles of each element by the number of moles for the element present in the smallest molar amount. In this case there is less Mn than O, so divide by the number of moles of Mn:1.1 mol Mn/1.1 = 1 mol Mn2.3 mol O/1.1 = 2.1 mol OThe best ratio is Mn:O of 1:2 and the formula is MnO2

The empirical formula is MnO2

Based on the given example solve the following problems in finding the empirical formula of a compound

1. What is the empirical formula of a compound containing 60.0% sulfur and 40.0% oxygen by mass?

2. A compound is found to contain 23.3% magnesium, 30.7% sulfur and 46.0% oxygen. What is the empirical formula of this compound?

3. What is the empirical formula for a compound containing 38.8% carbon, 16.2% hydrogen and 45.1% nitrogen?

4. A sample of an oxide of nitrogen is found to contain 30.4% nitrogen. What is its empirical formula?

5. A sample of an oxide of arsenic is found to contain 75.74% arsenic. What is its empirical formula?

ASSESSMENT CARD

Solve the following problems based on what you learned from the previous activities.

1. What are the mass % of carbon and oxygen in carbon dioxide, CO2?2. The simplest formula for vitamin C is C3H4O3. Experimental

data indicates that the molecular mass of vitamin C is about 180. What is the molecular formula of vitamin C?

3. A compound is analyzed and found to have a mass of 289.9 grams/mole and contain 49.67% carbon, 48.92% chlorine and 1.39% hydrogen. What is the molecular formula of the compound?

4. A compound is analyzed 21.6% Na, 33.3% Cl, and 45.1% O. Calculate its empirical formula.

5. What is the empirical formula of a compound that is 53.73% Fe, and 46.29% S?

Did you get all correctly? If yes, very good!

ENRICHMENT CARD:

Going Further……

1. What is the element that has the electron configuration 1s2 2s2 2p6?

a. Ne b. Na c. F d. N

2. A compound contains 40% C, 6.7% H and 53.3% O. Its molar mass is 60 g/mol. What is the molecular formula of the compound?

a. C2H3O2 c. C3H8O2

b. C2HO d. C2H4O2

3. A compound having a formula mass of 40 is

a. Fe2O3 c. C6H2O6

b. NaOH d. H2O

4. Toothpaste contains an active ingredient sodium fluoride, NaF. What is the percentage composition of fluorine in toothpaste/

a. 45.24% c. 40%

b. 54.76% d. 56.58%

5. Which of the following compounds has the lowest percentage of carbon?

a. CO2 c. CH4

b. CaCO3 d. CO3

AGREEMENT CARD

Direction: Solve the following problems correctly.

1. Calculate the formula mass of the following compounds.

a. NaOH

b. FeO2

c. C6H2O6

2. A compound is 32.39% Na, 22.57% S, and 45.07% O. Find its

empirical formula?

3. A hydrocarbon compound substance that contains only

carbon and hydrogen is 75% C. What is the empirical formula

of a compound?

4. Write the electronic configuration of 20Ca.

5. What is the missing part in the electron configuration of 16S?

REFERENCE CARD:

Basic Model of the Atom

Introduction to Atoms

All matter consists of particles called atoms. This is a list of the basic characteristics of atoms:

Atoms cannot be divided using chemicals. They do consist of parts, which include protons, neutrons, and electrons, but an atom is a basic chemical building block of matter.

Each electron has a negative electrical charge. Each proton has a positive electrical charge. The charge of a proton

and an electron are equal in magnitude, yet opposite in sign. Electrons and protons are electrically attracted to each other.

Each neutron is electrically neutral. In other words, neutrons do not have a charge and are not electrically attracted to either electrons or protons.

Protons and neutrons are about the same size as each other and are much larger than electrons. The mass of a proton is essentially the same as that of a neutron. The mass of a proton is 1840 times greater than the mass of an electron.

The nucleus of an atom contains protons and neutrons. The nucleus carries a positive electrical charge.

Electrons move around outside the nucleus.

Almost all of the mass of an atom is in its nucleus; almost all of the volume of an atom is occupied by electrons.

The number of protons (also known as its atomic number) determines the element. Varying the number of neutrons results in isotopes. Varying the number of electrons results in ions. Isotopes and ions of an atom with a constant number of protons are all variations of a single element.

The particles within an atom are bound together by powerful forces. In general, electrons are easier to add or remove from an atom than a proton or neutron. Chemical reactions largely involve atoms or groups of atoms and the interactions between their electrons.

Definition of Molecular FormulaDefinition: An expression which states the number and type of atoms present in a molecule of a substance.

Read more…….

Chemistry by: Amelia P. Mapa, Trinidad B. Fedelino, Lilia M. Rabago pp. 67-76 and pp. 149-153Chemistry for the New Millennium, Emil F. Soriano, Celeste Joan C. Santisteban, Erla Rhysa R. Elauria: pp. 85-93 and pp. 177-184You and the Natural World-Chemistry, Estrella E. Mendoza, Teresita F. Religioso: pp. 68-81

ANSWER CARD:

How well did you score?

Activity no. 1

1. 1s22s22p63s23p3

2. 1s22s22p63s2

3. 1s22s22p63s23p64s23d5

4. 1s22s22p63s23p64s1

5. 1s22s22p63s24s23d6

Activity no. 2

1. Ca-40%, C-12%, O-48%2. C-52.17%, H-13.04%, O-34.78%3. H-2.44%, O-58.54%, O-39.02%4. C-64.86%, H-13.51%, O-21.62%5. H-1.45%, Mg-26.09%, S-20.29%, O-52.1%

Activity no. 3

1. SO3

2. MgSO3

3. CH5N4. NO2

5. As2O3

Assessment Card

1. Mass % of C = 27.29% and O = 72.71%2. C6H8O6

3. C12H4Cl4

4. NaClO4

5. Fe2O3

Enrichment card

1. A2. D3. B4. A5. B