GENERAL CHEMISTRY explained in 19 Minutes | Highlights and Annotations by Gistr.

This segment provides a comprehensive explanation of quantum numbers (n, l, ml, ms), their significance in describing electron behavior within an atom, and how they relate to the Aufbau principle for determining electron configuration. It details how to determine the electron configuration of an element using the periodic table and the concept of valence electrons, particularly for transition metals, making it a valuable resource for understanding atomic structure and electron arrangement. This segment explains the concept of activation energy, differentiating between exothermic and endothermic reactions using analogies to illustrate energy changes and spontaneity. same molecular formula, but obviously, they’re not the same. they’re isomers. showing this difference is probably kind of important: it’s the only thing that separates graphite from diamonds, because they’re both just fancy versions of carbon, and I don’t think anyone’s going to go “mmm, yes, this dusty black blob is indeed very expensive”. one way to show the structure of an atom is a Lewis-dot-structure, which represents the valence electrons and bonds as dots and lines. that is also going to help us understand why atoms bond in the first place. you see, everything in the universe wants to get to a state of lower energy. that’s why a ball on a hill will roll down by itself, because that decreases its potential energy. this trend also applies to atoms: the state of lowest potential energy is having a full outer shell of electrons, which is most often eight, or in the case of hydrogen and helium, two. if you think back to the periodic table, you’ll see that all noble gases already have a full outer shell, which is why they don’t really want to react with anything. if two atoms don’t have a full outer shell, but can achieve one by sharing electrons, they will naturally do so, the same way a ball will go downhill, as their combined energy would be lower than if they were separate. the sharing of electrons is called a “covalent bond”. these bonds are also caused by the positively charged nucleus of an atom tugging on electrons of another atom. the strength of this pull is called “electronegativity”. in the periodic table, the electronegativity increases from bottom left to the top right. therefore, fluorine has the strongest pull. it’s just, unbelievably desperate for an electron. if the difference it a partial negative charge, and leaving hydrogen with a partial positive charge. the presence of two poles with opposite charge is called a “electric dipole”. all permanent dipole molecules can interact with each other, and really, with anything that has a charge.. as a result, the molecules will tug on each other and arrange themselves in a way that oppositely charged ends are next to each other. the forces acting between them are called “intermolecular forces” or IMFS. a specific example is hydrogen bonds, where hydrogen bonds to something very electronegative, like fluorine, oxygen or nitrogen, creating strong dipoles that tug on each other. but even if molecules are not polar at all, there can be electrostatic forces acting between them.. how? electrons move around inside atoms, and by pure chance they can end up on one side of the atom, creating a momentary dipole, which influences other particles next to it to become a dipole as well. at least for a very short time, as the electrons keep moving and the dipole disappears. this is called “van der Waals forces”. the polarity of water also explains why it’s one of the most versatile to a higher energy state. once they falls back down, the difference in energy is released as light. the colour of the light depends on the element that’s used in the tube, as each element has different, but fixed energy levels, and the difference between those determines the energy and therefore the frequency of the released light, which is what changes the colour. all possible frequencies, that an element can emit, are called the “emission spectrum”. all matter can be divided into two categories: pure substances, which can consist of one element or one compound, and mixtures. mixtures consist of at least two pure substances and can be homogeneous or heterogeneous. homogeneous means the substances will mix evenly and the mixture looks the same everywhere, like salt in water, which is a “solution”. heterogeneous mixtures look different depending on where you look. they have distinct regions made of separate substances. one example is sand in water, which is called a “suspension”. okay, well what about milk? that looks the same everywhere, so it must be homogeneous! uhhh, no. milk is something we call a “colloid”, or more precisely an “emulsion”. the difference between salt water and milk is that the solute doesn’t fully dissolve in the solvent, meaning there are bigger particles than in a solution, but smaller particles than in a suspension. this allows the particles to stay evenly distributed, but not fully dissolved, placing them somewhere between solutions and suspensions. hey remember sodium and water? what’s going on here? explosions are really just chemical reactions that release a lot of energy in a very short amount of time. also, they expand, like, Brondsted-Lowry, an acid is a molecule that donates protons, while bases accept protons. a proton in this case is just a hydrogen ion. so, with this definition, a molecule with at least one hydrogen that it can throw away can be an acid, and anything that can pick it up can be a base. this also means that once they react, they turn into the conjugate opposite, as an acid that gave away a proton can now accept one back, which is what bases do. a molecule that can act as both an acid and a base is called "amphoteric". a strong acid will dissociate almost completely into its ionic form, giving off a lot of protons to the water and therefore creating lots of hydronium ions. a weak acid just won’t dissociate nearly as much, giving us a lower concentration of hydronium ions. so, to measure the strength of an acid we can measure the concentration of hydronium ions. this is called the “ph”. mathematically, it’s defined as the negative log of the hydronium concentration, which means one step on the scale is a 10x change, and also, since it’s a negative log, the higher the concentration, the lower the ph. for example. pure water is in a chemical equilibrium. there’s exactly one hydronium ion for every 10 million water molecules. in other words, the concentration of hydronium is 1 over 10 million, or 1 times 10^-7. taking the negative log of this gives us a ph of 7, which is considered neutral. anything lower than 7 is acidic, and anything above is “basic”, unlike you. you can do the same thing with hydroxide ions and you will get the POH, which keep track of basicity. fun fact! the ph and POH always add up to 14, because they counteract each other, so by knowing one, you know both! now, if you have a strong base and a strong acid and you pour them together, no, they will not explode, they will neutralize by forming water along with a salt, which is neutral. for example, hydrochloride and sodium hydroxide will