Okay chemistry time! I used to be very good at chemistry in high school so this was nostalgic to go through this process. Let's talk about limestone since the cool cliffs in Khao Sok National Park are made of limestone. Limestone primarily consists of calcium carbonate (CaCO3), thought it can contain other minerals too. In the carbonate ion (CO3)2-, carbon uses sp2 hybridization to form three sigma bonds with oxygen. This means the carbon atom mixes one s orbital and two p atomic orbitals to form three equivalent hybrid orbitals. Due to this hybridization of the orbitals, the three oxygen atoms are arraigned in a trigonal planar fashion at 120 degrees around the carbon atom. The hybridization allows the carbon atom to form 3 sigma bonds to the oxygens, the strongest type of covalent chemical bond. Next, the carbonate ion exists in a state of resonance, there is not a single, static structure of the ion. Instead, its structure can be represented in three different ways, where the electrons are delocalized over the ion. The electrons are spread out or 'delocalized' over all three oxygen atoms, making all the C-O bonds identical in nature, neither fully single nor fully double but something in between, often described as 1.33 bonds All C-O bonds are the same length, which is longer than a typical C=O double bond but shorter than a C-O single bond, reflecting their intermediate character. Cool, now this was just about the how carbon bonds to the three oxygen molecules. Next, each oxygen molecule has two lone pairs of electrons. After forming three sigma bonds with its sp2 hybrid orbitals, the carbon atom has one p orbital left that is unhybridized. The unhybridized p orbital on carbon then can overlap with the p orbitals ( the two lone pairs of electrons) of the oxygen atoms. These p orbitals from oxygen and carbon overlap side-to-side (not head-on like sigma bonds), forming pi (π) bonds.The electrons in this unhybridized p orbital, along with the additional electrons from the ion's charge, contribute to a delocalized pi system. This system allows the electrons to resonate across the entire molecule, giving all C-O bonds their partial double bond character.. In summary, sp2 hybridization sets up the geometry and bonding framework for CO₃²⁻, allowing for the formation of a pi system. Resonance is then the phenomenon where the electrons in this pi system are not fixed but are delocalized across the molecule, leading to the observed properties of the carbonate ion. Now calcite is the most common form of limestone. Calcite has a rhombohedral crystal system, specifically a form of trigonal symmetry. Calcite crystallizes in a structure where each calcium ion (Ca²⁺) is surrounded by six oxygen atoms from carbonate ions in a slightly distorted octahedral geometry. This is due to the way carbonate anions (CO₃²⁻) are arranged in layers. The bonds in calcite are ionic between calcium and carbonate but covalent as discussed within the carbonate ion. Lastly, the limestone cliffs of Khao Sok can get their beautiful jagged features because Calcite's rhombohedral cleavage can lead to interesting patterns where layers might separate or fracture in a visually appealing manner, especially under the influence of tectonic forces or erosion. Also, the chemical properties driven by the carbonate ion's geometry enable limestone to dissolve in slightly acidic water, forming caves!
I just returned from a 2 day 1 night jungle floating bungalow stay in Khao Sok National Park. I was on a tour with about 60 people where we went on boating safaris, caving, jungle trekking, kayaking and a stay on a floating bungalow. A quick history on the area. Khao Sok is one of the oldest rainforests in the world, dating back 160 million years. The iconic limestone cliffs predate the jungle, dating back around 250 million years. Over time, tectonic movements caused the limestone to uplift above sea level. The formations were shaped into towering cliffs and ridges by geological processes. In the 1980s, the construction of the Ratchaprapha Dam created Cheow Lan Lake within Khao Sok National Park. The dam was built for hydroelectric power generation, and the lake flooded a large valley, submerging forests and lowland areas. I arrived at Cheow Lan Lake and boarded a long boat. The scenes were stunning and I felt like I was in a scene of Avatar. The limestone cliffs were covered in green brush, it made me think about the amazingness of nature and rocks. There is no way this is all entropy, right? In a separate post I am going to explore the chemistry of limestone because I think it is fascinating. We drove around the lake for a while and took a 20 minute pitstop at diamond cave. It was a really dark and authentic cave with nice stalactites and stalagmites. After the cave the group and myself went to check in to our floating bungalows. I stayed in a room with two other solo travelers, Joel from Sweden and Carl from Ireland. The room was tiny and solely had three mattresses on the floor. We got to get to know each other and hopped in the water to cool off. Around 1600 we went to the jungle trek. We saw otters, monkeys, and the biggest spider I have ever seen in my life. It was nice but I was quite tired from a long day in the sun and a shitty night sleep in my hostel. In the evening I ate dinner and chatted with a cool couple, Marcello and Margarita from Northern Italy. They gave me some recommendations such as the Similian Islands in Thailand, where you camp on the beach with a local tribe. Joel also gave me some recommendations about Laos and Cambodia, highlighting a motorbike loop in central Laos and the islands of Koh Rong in Southern Cambodia. After, Carl and I talked about geopolitics, tech, and traveling. Carl is also an electrical engineer who worked at Intel in Ireland, but was fed up with the office life, like me. He quit his job to travel the world for 10 months and found a passion in emergency medicine. We talked about both fields and the lifestyles that come with it. He told me about the history of Ireland which is very interesting. I would like to go to Ireland, but unfortunately they are anti-Israel. I asked him if it was true and he said yes, because Ireland used to be "occupied" they sympathize with the Palestinian cause. Another interesting topic was the EU Apple Ireland Tax Case. Ireland has an outstanding corporate tax of 12.5%, which attracts tons of American companies and tech companies to have European HQs in Ireland. Ireland is a part of the EU and in 2016 the EU investigated Apple over not paying enough tax to Ireland. The case was Ireland and Apple against the EU. In the end the EU ruled Apple needed to pay Ireland 13 million Euros, even though Ireland was on Apple's side! Now Ireland does not know what to do or how to distribute the money since they did not even want it! We also talked about Irish pub culture and American sports, it was very nice. I realized and reaffirmed through this I typically connect with older people since they typically have more depth and interesting stories than people my age. In the middle of the night I got up to pee and the sky was covered with the brightest stars I have ever seen. It was so clear and felt so close. Every single spot in the sky had a star, I had never seen the sky so full! In the morning today we woke up early and did another boat safari. We saw some more monkeys and otters. I fly to Chiang Mai Saturday night so will take the next days to chill and prepare for the next leg!
