Ever wondered what our young Sun might have looked like in its infancy some five billion years ago?
The audacious JWST has captured an image of a very young star much like our young Sun, though the star itself is obscured. Instead, we see supersonic jets of gas. Young stars can blast out jets of material as they form, and the jets light up the surrounding gas. The luminous regions created by the jets as they slam into the gas are called Herbig-Haro Objects.
For millennia, scientists have pondered the mystery of life – namely, what goes into making it? According to most ancient cultures, life and all existence was made up of the basic elements of nature – i.e. Earth, Air, Wind, Water, and Fire. However, in time, many philosophers began to put forth the notion that all things were composed of tiny, indivisible things that could neither be created nor destroyed (i.e. particles).
However, this was a largely philosophical notion, and it was not until the emergence of atomic theory and modern chemistry that scientists began to postulate that particles, when taken in combination, produced the basic building blocks of all things. Molecules, they called them, taken from the Latin “moles” (which means “mass” or “barrier”). But used in the context of modern particle theory, the term refers to small units of mass.
By its classical definition, a molecule is the smallest particle of a substance that retains the chemical and physical properties of that substance. They are composed of two or more atoms, a group of like or different atoms held together by chemical forces.
It may consist of atoms of a single chemical element, as with oxygen (O2), or of different elements, as with water (H2O). As components of matter, molecules are common in organic substances (and therefore biochemistry) and are what allow for life-giving elements, like liquid water and breathable atmospheres.
Types of Bonds:
Molecules are held together by one of two types of bonds – covalent bonds or ionic bonds. A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. And the bond they form, which is the result of a stable balance of attractive and repulsive forces between atoms, is known as covalent bonding.
Ionic bonding, by contrast, is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions. The ions involved in this kind of bond are atoms that have lost one or more electrons (called cations), and those that have gained one or more electrons (called anions). In contrast to covalence, this transfer is termed electrovalance.
In the simplest of forms, covelant bonds take place between a metal atom (as the cation) and a nonmetal atom (the anion), leading to compounds like Sodium Chloride (NaCl) or Iron Oxide (Fe²O³) – aka. salt and rust. However, more complex arrangements can be made too, such as ammonium (NH4+) or hydrocarbons like methane (CH4) and ethane (H³CCH³).
History of Study
Historically, molecular theory and atomic theory are intertwined. The first recorded mention of matter being made up of “discreet units” began in ancient India where practitioners of Jainism espoused the notion that all things were composed of small indivisible elements that combined to form more complex objects.
In ancient Greece, philosophers Leucippus and Democritus coined the term “atomos” when referring to the “smallest indivisible parts of matter”, from which we derive the modern term atom.
Then in 1661, naturalist Robert Boyle argued in a treatise on chemistry – titled “The Sceptical Chymist“- that matter was composed of various combinations of “corpuscules”, rather than earth, air, wind, water and fire. However. these observations were confined to the field of philosophy.
It was not until the late 18th and early 19th century when Antoine Lavoisier’s Law of Conservation of Mass and Dalton’s Law of Multiple Proportions brought atoms and molecules into the field of hard science. The former proposed that elements are basic substances that cannot be broken down further while the latter proposed that each element consists of a single, unique type, of atom and that these can join together to form chemical compounds.
A further boon came in 1865 when Johann Josef Loschmidt measured the size of the molecules that make up air, thus giving a sense of scale to molecules. The invention of the Scanning Tunneling Microscope (STM) in 1981 allowed for atoms and molecules to be observed directly for the first time as well.
Today, our concept of molecules is being refined further thanks to ongoing research in the fields of quantum physics, organic chemistry and biochemistry. And when it comes to the search for life on other worlds, an understanding of what organic molecules need in order to emerge from the combination of chemical building blocks, is essential.
Humans, cars and planets are made of molecules. And molecules are made of atoms. Atoms are made of protons, neutrons and electrons. What are they made of? This is the standard model of particle physics, which explains how everything is put together and the forces that mediate all those particles. Continue reading “Astronomy Cast Ep. 392: The Standard Model – Intro”
Emily Lakdawalla is the senior editor and planetary evangelist for the Planetary Society. She’s also one of the most knowledgeable people I know about everything that’s going on in the Solar System. From Curiosity’s exploration of Mars to the search for life in the icy outer reaches of the Solar System, Emily can give you the inside scoop.
In this short interview, Emily describes where she thinks we should be looking for life in the Solar System.
[/caption]It has long been known that all molecules possess two equal and opposite charges which are separated by a certain distance. This separation of positive and negative charges is what is referred to as an electric dipole, meaning that it essentially has two poles. In the case of such polar molecules, the center of negative charge does not coincide with the center of positive charge. The extent of polarity in such covalent molecules can be described by the term Dipole Moment, which is essentially the measure of polarity in a polar covalent bond.
The simplest example of a dipole is a water molecule. A molecule of water is polar because of the unequal sharing of its electrons in a “bent” structure. The water molecule forms an angle, with hydrogen atoms at the tips and oxygen at the vertex. Since oxygen has a higher electronegativity than hydrogen, the side of the molecule with the oxygen atom has a partial negative charge while the hydrogen, in the center, has a partial positive charge. Because of this, the direction of the dipole moment points towards the oxygen.
In the language of physics, the electric dipole moment is a measure of the separation of positive and negative electrical charges in a system of charges, that is, a measure of the charge system’s overall polarity – i.e. the separation of the molecules electric charge, which leads to a dipole. Mathematically, and in the simple case of two point charges, one with charge +q and one with charge ?q, the electric dipole moment p can be expressed as:p=qd, where d is the displacement vector pointing from the negative charge to the positive charge. Thus, the electric dipole moment vector p points from the negative charge to the positive charge.
Another way to look at it is to represent the Dipole Moment by the Greek letter m, m = ed, where e is the electrical charge and d is the distance of separation. It is expressed in the units of Debye and written as D (where 1 Debye = 1 x 10-18e.s.u cm). A dipole moment is a vector quantity and is therefore represented by a small arrow with a tail at the positive center and head pointing towards a negative center. In the case of a Water molecule, the Dipole moment is 1.85 D, whereas a molecule of hydrochloric acid is 1.03 D and can be represented as:
We have written many articles about dipole moment for Universe Today. Here’s an article about what water is made of, and here’s an article about molecules.