Why do we tend look for somebody to be with? A friend, someone so dear or anyone that comes along that is be fun to be with, just makes us feel good. Even the invisible particles called atoms would likely have the same tendency – to look for a partner. This brings us to another question: “Why atoms combine with one another?”
An atom that combines with another atom becomes more stable, just as two people who become steady when they bond with each other. When atoms chemically combine, they form bond, which is an attractive force that holds them together. This is the status of most atoms. There are a few however, which are stable in their single status – the noble gases such as helium, neon, argon, krypton, xenon and radon.
When atoms combine, they either transfer-accept or share electrons. The transfer of electron by a metallic atom to a nonmetal results in ionic bonding, while the sharing of electrons between nonmetals causes the formation of covalent bond. There is no transferring of electrons among nonmetals because of their high electronegativities, or tendencies to pull electrons toward themselves when combined with another atoms. There is also that metallic bond, which is the attraction between the framework of positive charges and the surrounding, moving sea of valence electrons among metals.
Christmas is the time of joy. We see colorful lights and parols/lanterns everywhere. The bells of churches ring, advent candles are lighted and we hear melodious songs of gladness in commemoration of the birth of Jesus, the Messiah.
Chemical reactions take place anywhere. Candles continue to burn as the wax reacts with oxygen in the cold air. Firework displays are also a common sight. The night sky is painted with bright colors as the electrons of the atoms that make up the fire crackers become excited when heated. At Noche Buena, our Ate’s and mothers combine in certain proportions the right stuff for Leche Flan, delicious Ham, and those traditional puto and suman. How carefully they are chemically changed to come up with a sumptuous dinner.
But what is the right chemistry for Christmas? We celebrate this season not for the food or the colorful decorations around. This is the time for rejoicing for unto us, a Messiah is born, who is Christ our Savior. Let us take a look at the chemistry of people in the Nativity Scene- Joseph, Mary, the shepherds, the wise men, to name some. They are all looking at the Child Jesus. They did not just become witnesses of Christ’s birth, they too shared in the fulfillment of what was prophesied long, long ago.
Have a happy Christmas Kemikastudents! (No quiz here. 
)
Yes, that’s atomatic, as in counting atomic particles.
Atomatically, the number of electrons, e- is the same as the number of protons, p+. An atom is electrically neutral. In other words, its net charge is zero.
When the number of e- and p+ and are added, the sum is zero because they are of opposite charges. – 2 + 2 = 0, right?
When an atom ionizes (by loss or gain of e-), its number of p+ does not change at all. All isotopes of an atom have different number of neutrons, but their number of p+ is the same. Because of this, the atomic number is atomatically equal to the number of protons. An atom with atomic number 8 (Oxygen, O), has 8 electrons and 8 protons.
The mass of the atom is concentrated at its center or nucleus. The nucleus contains the protons, p+ and neutrons, n0. So, the mass number = of p+ + n0. The mass number of Aluminum, Al is 27. Its number of p+ is 13. How many n0 does it have in the nucleus? Yes, 14 because 14 n plus 13 p = 27 mass number.
Can you atomatically count the particles in the following?
| Atom | Atomic Number | No. of p+ | No. of n0 | Mass Number | No. of e- |
Ca |
20 |
|
20 |
|
|
K |
|
19 |
|
39 |
|
Na |
|
|
12 |
|
23 |
Count atomatically now. Take the quiz below. (I suggest that you write down your answers on a piece of paper then have them entered in the boxes provided for, in the online quiz form.)
Give the number in each box/ cell to complete the table.
| Item No. | Atom | Atomic Number | No. of p+ | No. of n0 | Mass Number | No. of e- |
| Example | F | 9 | 10 | |||
| 1 | C | 6 | 13 | |||
| 2 | H | 1 | 0 | |||
| 3 | S | 16 | 16 | |||
| 4 | Mg | 12 | 24 | |||
| 5 | Be | 4 | 9 |
Answer to the EXAMPLE: 9, 19, 9
Quiz: Count Atomatically by completing the table above. (Submit your answers here.)
Over the years, various scientists have presented models to somehow give a picture of the structure of the unseen atom. Well, we can actually see their models of atomic structure just around.
I took these pics using my N70 phone. You wouldn’t think they can be likened with the atomic models of Dalton, Thomson, Rutherford, Bohr and even the modern atomic model.
Dalton: A Solid Sphere. You might have come across with some spheres such as in the picture. The spheres are actually crystal balls used by a student in her TLE project. Those are spheres of mass – Dalton’s Atomic Model. He added that atoms are indestructible. Are they really unbreakable? Read about radioactivity to find out. In addition, Dalton proposed that each atom has hooks, which enabled it to combine with other atoms.
Thomson: Raisin Bread. Sliced breads are made special with raisins. Thomson’s Model shows electrons or negative charges scattered on a positive sphere. The bread is the positive matrix and the raisins are comparable to the electrons.
Rutherford: A Tiny Massive Center. My co-teacher Mr. Velasco sometimes plays dart during his spare time. The dart board is similar to that of Rutherford’s Model. Just as in dart, Rutherford fired alpha particles on the atoms of gold foil. There were no alpha particles deflected at first; the bullseyes were not hit, in other words. Hence he said, “An atom is almost an empty space.” Later, as he continued to cast alpha particles, very few particles bounced back, indicating that they hit tiny, massive centers called nuclei (nucleus in singular).
Bohr: Electrons in Orbits. I took this picture at St. Joseph’s Rectory in Ipil. The curved ladders reminded me of the atom’s circular orbits, like those described by Neils Bohr. Bohr said that electrons are allowed to occupy at certain orbits around the nucleus. Meaning, electrons at lower levels have lower energy than those at the outer orbits. Another familiar sight is the solar system. The sun is like the nucleus and the orbiting planets, the electrons.
Modern Atom: Electron Cloud Model. Electrons are difficult to locate because they spin at great speeds around the atom’s center, just like the blades of the electric fan in the picture. You could hardly locate the position of each blade as they rotate around. Just like the electrons, the blades form a “cloud” as they circle around. A cloud of electrons is called orbital.
Kemikwiz: Visible Atoms huh!?
What similarities are there between a school and an atom? Read below.
| School | Atom |
| Floors (1st, 2nd , 3rd floor) | Energy Levels (1, 2, 3… or K, L, M…) |
| Rooms ( Room 1A, 1B, etc… in the 1st Floor) | Sublevels ( 3s, 3p, 3d in the 3rd Energy level) |
| Chairs (A1, A2…) | Orbitals (s, p, d, f, g…) |
| Students (use the Chairs) | Electrons (occupy the Orbitals) |
So if you want to easily recall how electrons reside in an atom, you simply have to remember your school. But as a chemistry student, you also keep in mind the information about an atom.
FIRST – The floors or the energy level (n), also called shell, determines the number of sublevels. If n = 1 then there is only 1 sublevel. If n = 5, there are also 5 sublevels.
SECOND -The sublevels or the rooms of an atom are following s, p, d, f, g, h, i, j and so on. If n = 2, the sublevels would be 2s, 2p. Why is there no 2d? You’re right, the 2nd energy level has only 2 sublevels. Therefore if n=1, there’s only 1s, nothing more. Easy, right? Try more here.
THIRD – The orbitals or chairs s, p, d, f… are regions in space where electrons are most probably found. The s, p, d, f… contain 1, 3, 5, 7… orbitals, respectively.
LAST – The electrons or the students are occupants of orbitals or chairs. In each orbital, a maximum of two electrons can occupy. If the schools were exactly the same as atoms, then the first floor (n=1) would only have 1 room (sublevel), 1 chair (orbital) and 2 students (electrons). How (un)fortunate!
Can you tell the maximum number of electrons in the following?
- n = 2
- 2s
- 4s, 4p, 4d
- f
Take the kemikuiz.
Have you ever asked how breathing works?
Imagine your lungs like an elastic balloon. What can be done with a balloon? Yeah, that’s right! You can either squeeze or expand it. In your Biology, you have learned that your diaphragm is made up of muscles. Within your ribs are intercostal muscles. The muscles of the ribs and diaphragm are vital to your breathing.
Remember the movements of muscles? They either contract or relax. What happens when your diaphragm and rib muscles contract? Your diaphragm lowers and its ribs are raised causing the lungs to expand. With this, the lungs have a lower pressure compared to that of the air (outside the body), because the lungs have a greater volume. Air rushes into the lungs; you inhale so to speak. Gases move from an area of higher pressure to an area of lower pressure. Low pressure areas like the Philippines are prone to being blown with strong winds. When the muscles are relaxed, the volume of air in the lungs lowers. Because the pressure in the lungs is higher than the air pressure, you exhale. Air is cast out.
Let’s pick out the major points above. Lower pressure results in greater volume. When the pressure is higher, the volume gets lower. This is what Boyle’s Law is. At constant temperature, volume is inversely proportional to pressure. 
Looking for new volume:
Want to solve Boyle’s Law problems? Click here.
Let’s watch my nephew’s (Nonoy) video, which demonstrates Boyle’s Law.
As Nonoy applies more pressure on the piston, the volume of the gas in the syringe gets lower.
Click here for more Boyle’s Law discussion
Your kemikalidad is once again under pressure with the quiz below.
Last August 13, this year, my brother in law Macoy was driving a motorcycle from Zamboanga City. My sister Dionessa and their one-year old son Joshua accompanied him. The two were riding at his back. It was already like 10 am, and so the road was really hot. They were halfway homeward when the back tire exploded. My sister secured her son with her arms shielding around as she, and Macoy were thrown onto the concrete road. Thank God Joshua was not hurt at all. The couple however were bruised and injured. Good thing the people who saw them came to help. They are so OK now.
Macoy's Motorcycle
So what caused the tire blowout? What actually happened to the interior tire, which was practically in contact with the hot road? The interior is made up of gases, which would expand when heated. As the temperature increased, so did the volume of the gas inside the tire. The tire could not anymore hold the increased gas volume and so it exploded. How much volume would be increased by a given temperature rise?
Let’s find out. Charles’ Law tells that, “at constant pressure, the volume of a gas is directly proportional to the Kelvin temperature.” The higher the temperature; the higher the volume.
To solve for an increase in temperature, the equation below could help.
The first volume V1 is multiplied by the quotient of T2 over T1. Isn’t that simple? Note that the temperature is expressed in Kelvin or K unit.
Let’s solve a problem. At constant pressure, a certain gas occupied a volume of 10.0 mL at 300.0 K. What will its volume be at 600.0 K?
Given
First Conditions Second Conditions
V1 = 10.0 mL V2 = ?
T1 = 300.0 K T2 = 600.0 K
Solving,
Finding it difficult? O’ come on Charles, you just have to divide 600 by 300 to get the quotient 2. Cancel both Kelvin units, K because K over K is 1. Then multiply 10 mL by 2; you get 20 mL. Volume increased from 10 mL to 20 mL. Remember what Charles’ Law is? When the Kelvin temperature increases, the volume of gas also increases, at constant pressure.
Link to quiz; test your kemikalidad.
Quiz: Charles’ Tire Blowout
I bet most of you have tasted that delicious mango float with Graham’s Flakes as its crust. Hungry already? Let’s take a crunchy bite with another Graham’s offering – Graham’s Law of Diffusion.
Take a look at the figure below.
Ammonia, NH3 when reacted with hydrogen chloride, HCl, will form a cloudy white substance, ammonium chloride, NH4Cl. Where do you think will the white substance form?
- Near NH3 end
- Near HCl end
- At the middle of the tube
Find the answer and explanation here.
It is therefore necessary that we measure the density of gases to compare their rates of diffusion. Below is an example how density of a gas at STP is solved.
Densities of CO (carbon monoxide) and CO2 (carbon dioxide) at STP
Given Molar Masses: C = 12; O = 16
Based on the results above, it can be said that CO, having lower density will diffuse or travel faster than CO2.
Graham’s Law of Diffusion asserts that the rates of diffusion of two gases are inversely proportional to the square root of their densities. Meaning, the gas with a lower density will have a greater rate of diffusion than a gas with higher density.
Explore your kemikalidad; take the test now.
Quiz: Crunchy Graham’s Test
One time I was driving on a highway and I saw a recognizable sign at the back of a truck. It read “STP”. I supposed it meant, “STOP”.
What’s this STP on gases? When we deal with gases, we would like to see how it behaves at certain temperature, T, or how it builds up pressure, P, at certain conditions. Standard Temperature and Pressure or STP should we go!
At STP, the T has a value of zero degrees Celsius which is equal to 273 Kelvin (Oo C = 273 K). That would freeze water. The P, pressure exerted by any gas at STP is 1 atmosphere or 760 Torricelli (1 atm = 760 torr). The amount of gas at STP is 1 mol, which occupies a volume of 22.4 liters. Imagine filling up twenty two 1-liter bottles and a 400 mL container with gas. This much is needed to trap 1 mol of carbon dioxide, CO2 or any gas in bottles.
Go, STP!
| Standards | Values |
| Temperature | 273 K |
| Pressure | 1 atm |
| Amount | 1 mol |
| Volume | 22.4 L |
So the next time you see STP, don’t stop; instead, remember the constants of gases. You might ask: “Why involve these constant values with gases?” In our other discussions about gases, we will use the values of STP to help us solve certain problems.
Now, take the quiz below to evaluate your chemicability in STP.
Quiz: STP and go!
How do we prepare solutions? This is one problem. But I tell you, a kid can make the right solution. There was a time when my six-year old nephew, Nonoy, asked for more iced tea. Everyone was busy at the time, so no one could help him. Without anyone’s knowing, he opened the ref and mixed powdered tea and cold water. He solved his problem, he prepared a solution.
Want more?
He mixed cold water and tea powder. He made a solution. So, what do we need to prepare a solution? The tea powder is the solute; the cold water, solvent. Remember the famous line? “Water is a universal solvent.” How much water would you need? Would this be as much as the tea powder? Of course, you need more water than tea powder. In a solution, the one with the greater amount and is used as dissolving a medium is the solvent. The one dissolved and is in smaller amount is the solute.
Can you identify the solutes and solvents in the following examples?
| Solutions | Solvent | Solute |
| 1. Seawater (made of salts dissolved in water) | ||
| 2. Vinegar (mixture of acid and water) | ||
| 3. Clean Air (composed of Nitrogen, Oxygen, and other gases) | ||
| 4. Tincture of Iodine (Alcohol + iodine) | ||
| 5. 40% Rubbing Alcohol (A solution of water and alcohol) |
Check your answers. Click here.
In your first year Science, you learned that 78% of the air is Nitrogen. That’s why it is the solvent for a clean air. Alcohol can also be a solvent. There are even many solutes (mostly organic) that are insoluble to water but can be dissolved by alcohol. Tincture is the name of a solution whose solvent is alcohol; aqueous if it is water.
We have once again discussed chemistry. So it’s time to test your abilidad in Kem!
