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Science and Technology

What is an atom?

What is an atom?

An atom can be described as an important piece of matter, matter is something that can be touched physically. The universe is made up of matter, apart from its energy, thus, practically everything that is found in the universe is made up of atoms.

Subatomic particles make up the atom, there are three types of particles; protons, neutron, and electrons. These particles are placed; protons and electrons create the nucleus – located in the center, while the electrons float above the nucleus. Protons have a positive charge +1, while the electrons have a negative charge -1, and the neutrons are neutral with no net charge 0. Generally, neutral atoms have equal amounts of protons, neutrons, and electrons. These atoms are comprised of even smaller particles, to include quarks.

It is suggested that atoms were created after the Big Bang, 13.7 billion years ago. These atoms were created as the universe cooled down, thus allowing quarks and electrons to form. a few milliseconds after the quarks were created they combined to form protons and neutrons, these particles then created the nuclei. 380,000 years surpassed, and the universe started to trap the electrons in orbits around the nuclei, creating atoms. These first atoms, were mainly helium and hydrogen, which are still the most abundant elements to be found within the universe. Research has suggested that the first stars were created from clouds of gas, estimated to be 150-200 million years after the Big Bang. Other atoms such as; oxygen, carbon, and iron, were produced later in the core of stars, and spread throughout the universe in an array of explosions, called supernovae.

So, as you may of guessed, your body is made up of atoms, and so is all of the living, and nonliving world. And these are often made up of larger formations called molecules. All atoms and molecules follow the basic rules of chemistry and physics, no matter there size. Atoms gain and lose electrons, and form new bonds with one another, this rule applies to living organisms and non-living organisms. Science has proven that the smallest of interactions, performed in a variety of ways many times between atoms – unicellular or larger organisms. Has made life what it is now. It has also been suggested that everything, everything is could be the bi-product of chemical and electrical interactions of many different types of atoms.

Atomic particles

The particles that make up the nucleus; protons, and neutrons are noticeably heavier than the orbiting electrons. Protons, and neutrons have the same mass, and have a mass larger than an electron, this mass is around 1,835 more. Considering this the electrons are extremely lightweight. as discussed above, atoms generally have an equal amount of protons, neutrons, and electrons. If protons are added to an atom, a new element will be formed. If a neutron is added an isotope will be created, the greatest effect of adding a neutron to an atom – is that of the hydrogen atom – if a neutron is added to a hydrogen atom (a single proton and electron), it will be tuned into the isotope deuterium. Deuterium is found in great abundance in the Earth’s oceans.


A physicist named Ernest Rutherford, discovered the nucleus in 1911. Ernest Rutherford named the positive particle in 1920, and called it a neutron. He also theorized that the nucleus contained a neutral particle, this was named the neutron, James Chadwick, a British physicist, and a student of Ernest Rutherford confirmed this in 1932.

Typically the majority of the mass of an atom resides within the nucleus. The protons and neutrons that create the nucleus have the same momentum and are almost the same mass, with the protons having slightly less.

The nucleus is binded by a massive force. As per the laws of electricity, the force of the protons and neutrons overcomes the repulsive electrical force, that would normally repel the protons and neutrons. There are some nuclei that are unstable, this is because the force holding the neutrons and protons varies, this is generally because the size of the nuclei changes. Unstable nuclei, normally catalyze into different elements, such as, carbon-14 catalyzing into nitrogen-14.


Protons are positively charged particles and are located within the atoms atomic nuclei, they are around 99.86% of the mass of neutrons. They were first discovered using cathode-ray tubes between 1911 and 1919 – by Ernest Rutherford.

Each different type of atom has its own unique number of protons, an example of this is; oxygen atoms have eight protons, potassium has 19 protons, Gold has 79 protons, and krypton has 36 protons. When asked what the atomic number of an element is, you will answer with the number of protons it has. The chemical behavior of each element is determined via the number of protons. You can find elements listed in the Periodic Table of the Elements, and they will be listed in chronological order of atomic numbers.

To make a proton, three quarks are utilized, two “up” quarks – both with two-thirds positive charge, and one “down” charge  quark – with one-third negative charge. These quarks are stuck together subatomic particles named gluons, which have no mass.


The electrons within an atom are very small compared to its protons and neutrons, in fact, they are 1.800 times smaller.

The electron was first discovered in 1897 by physicist Joseph John (J.J), Electrons were formally named corpuscles, and possess a negative charged, they are electrically attracted to the electrically positive neutrons.  The electrons encircle the atoms atomic nucleus in pathways named orbitals, this theory was first devised in the 1920s by Erwin Schrödinger, who was an Austrian physicist. This theory is known today as the quantum model, or electron cloud model.

Valence Electrons

Inner orbital pathways encircle the atom, however, the outer orbitals shell, determine the chemical properties of the atom, this is called the valence shell.  Valence shells are the outermost shell of an atom, and contain valence electrons, these valence electrons can only be found in P and S block elements, listed on the periodic table, and are involved in bonding.  Elements with complete valence shells are least chemically reactive, while those with only one electron in its valence shell, or missing one electron from having a complete built shell, are always the most reactive. P or S block atom elements, can have between zero and seven valance electrons. When atoms have zero valence electrons they are called noble gases, these gases take an aversion to forming bonds, their valency is zero because their octet is complete. An Octet means the atoms outermost orbit has a complete set of 8 electrons, thus it is stable.


In 1920 Ruthord theorized the neutron, and in 1932 Chadwick discovered it. The neutron was discovered during experiments, the experiment in question involved atoms being shot at a thin sheet of beryllium, and subatomic particles were released – with no charge, is the neutron. This discovery leads to the theory that neutrons being uncharged particles, located within all atomic nuclei, apart from ordinary hydrogen. Protons are slightly smaller than the neutron, with a resting mass equal to 1.67493 × 10−27 kg. When the neutrons and protons are bound together within the inner core of an atom called the nucleus, they are called nucleons. These nucleons account for 99.9% of the atom’s total mass. And like protons, neutrons are created with quarks, one up quark (positive 2/3 charge), and two down quarks, each possessing negative one-third charge.

Changing atoms to different types of atoms

How does one change an atom into another atom? Well, normally you would start with the most basic atom, which is the hydrogen atom (H), the hydrogen atom consists of 1 electron and one proton, but has no neutrons. If a proton, another electron, and two more neutrons are added to the hydrogen atom it becomes Lithium (Li). If one more proton, one more neutron, and one more electron are added beryllium (be) will be created.

Atomic number and relative atomic mass

The law of science states that the number of protons and electrons are always the same, the number of neutrons is variable, but generally roughly the same as the number of protons, however, they can sometimes be greatly more. The number of protons within an atom, is called the atomic number and can be looked up using the periodic table, which allows you to determine the atom in question. When adding the number of protons and neutrons together it is called the relative atomic mass.

Videos to help you to understand the atom

A Tale of Two Atoms, National Geographic

Basics of the Universe, National Geographic

Electromagnetism basics, National Geographic

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