Category Chemistry

An element is a substance that is made up of only one kind of atom. The periodic table below shows all the elements currently known. However, there are more than 109 different atoms because some elements have more than one isotope.

There are more than 109 different types of atom – one for each element. Differences between the atoms give the elements their different chemical properties. In 2001, there were 115 known elements. However, those above 109 are highly unstable and have been made in only tiny quantities. Scientists are able to make tiny amounts of these new elements in the laboratory. They exist for only a very short time so, whilst they are of scientific interest, they have little practical use in the wider world – at the moment!

Atoms, once thought to be the smallest building blocks of nature, are in fact made of smaller particles. Most often these particles are in balance, and as such the atom is stable and lasts nearly forever. Some atoms are out of balance. This can make them radioactive.

Description: Atoms are made of tiny particles called protons, neutrons and electrons. Protons and neutrons clump together to form a central nucleus. The electrons move in a cloud-like region around the nucleus.

Stable: Most atoms are stable. Their protons, neutrons and electrons balance. Barring outside forces, a stable atom will stay the same indefinitely.

Isotopes: Every atom is a chemical element, like hydrogen, iron or chlorine. Every element has cousins called isotopes. These have a different number of neutrons, but are otherwise the same. Having excess neutrons may make isotopes radioactive.

Radioactive: Some atoms have too many neutrons in the nucleus, which makes them unstable. They’re radioactive, giving off particles until they become stable.

Ions: Atoms with extra or missing electrons are called ions. They have a positive or negative electric charge and are responsible for many chemical reactions.

Antimatter: Every atomic particle has a twin anti-particle, with an opposite electric charge. Antimatter hydrogen atoms have been formed in the laboratory, containing an anti-proton and anti-electron. Antimatter is very rare and fragile.

Each atom has a nucleus containing protons, and all except the hydrogen nucleuses have neutrons as well. Neutrons have no electrical charge, but protons have a positive charge. Moving at high speed around the nucleus are little particles of energy called electrons, which have a negative charge. The number of protons and electrons in an atom is always the same. As opposite charges attract each other, the attraction between the protons and the electrons keeps the electrons around the nucleus, just as the force of gravity keeps the Moon circling around the Earth.

The tiny atomic nucleus is the centre of an atom constituting positively charged particles “protons” and uncharged particles “neutrons.” On the other hand, the extra nucleus part is a much larger region which is composed of a cloud of negatively charged particles called an electron. Electrons revolve around the orbit or centre of the nucleus. The attraction between the protons and electrons holds the structure of an atom together.

Generally, all atoms are composed of these three subatomic particles except hydrogen. Hydrogen is an exception to all atoms as it just contains one proton and one electron but lacks neutrons. The number of protons indicates what element an atom is whereas the number of electrons indicates the type of reactions will happen in an atom.

The atomic nucleus in the structure of the atom is composed of a fixed number of protons and the proton attracts the same number of electrons thereby making an atom electrically neutral. Ions are formed by addition or removal of electrons from an atom.

There is no net charge of an atom. Electrons are the negatively charged particle whereas protons are the positively charged particles. The equal positive charge of the proton and the negative charge of the electron cancel each other. Therefore, the atom has no net charge. In an atom that is neutral, the number of electrons revolving around the nucleus and the number of protons inside the nucleus are equal in number.

The word “atom” comes from an ancient Greek word for a tiny piece of matter too small to be split up. Today we know that even atoms are made up of smaller parts, called subatomic particles. Protons and neutrons are the particles that make up the nucleus of an atom, while electrons can be thought of as circling around the nucleus like orbiting planets. However, these are not the only subatomic particles. Scientists have found hundreds more and are still discovering others by using a machine called a particle accelerator. Quarks, for example, form part of neutrons and protons.

When physicists first collided electrons with protons, they observed that electrons bounced off three small hard cores inside the proton. The cores were then called quarks and it was found to be even smaller particles that make up the proton. Quarks are the smallest particles we have come across in our scientific endeavor. Discovery of quarks meant that protons and neutrons weren’t fundamental anymore.

For more thorough understanding let’s peel apart a piece of matter and discover its constituents by removing each layer one by one. From a bird’s-eye view, matter looks rigid and its properties easily measurable. But even a 6-year-old can deduce that the tenacious pillars of his carefully engineered sandcastle are the sum of billions of microscopic sand grains. What constitutes the sand grain?

Peel another layer and you’ll find a neatly organized structure of atoms. The concept of atoms was first proposed by the Greeks, who believed that objects could be indefinitely split into halves until you were left with a single, indivisible speck of matter. This unimaginably small unit could not be divided further and was, therefore, called an “atom”, derived from the Greek word A-tomos. A for “no” and tomos for “cuttable” or splittable.

 Surprisingly, the theory didn’t fare well. Most of the texts written about elementary constituents were lost and retrieved after multiple centuries. It took almost two millennia for the atom to be was recognized as a real fundamental physical object.

The speculation was finally confirmed in the 1800s when chemist John Dalton conducted a series of ingenious experiments on gases. The average diameter of an atom measured around 50 nano-centimeters – a millionth of a grain of sand. The atom was then the smallest thing known to man.

Matter is the stuff that the universe is made of. The planets, this page, your body and the air that you breathe are all made of matter. Matter itself is made of very small particles called atoms, much too small to be seen with the naked eye or even with many microscopes. The kinds of atom that matter contains and the way in which they are joined together are what determine the kind of matter it is. Matter is a substance that has inertia and occupies physical space. According to modern physics, matter consists of various types of particles, each with mass and size.

The most familiar examples of material particles are the electron, the proton and the neutron. Combinations of these particles form atoms. There are more than 100 different kinds of atoms, each kind constituting a unique chemical element. A combination of atoms forms a molecule. Atoms and/or molecules can join together to form a compound.

Matter can exist in several states, also called phases. The three most common states are known as solid, liquid and gas. A single element or compound of matter might exist in more than one of the three states, depending on the temperature and pressure. Less familiar states of matter include plasma, foam and Bose-Einstein condensate. These states occur under special conditions.

Different kinds of matter can combine to form substances that may not resemble any of the original ingredients. For example, hydrogen (a gaseous element) and oxygen (another gaseous element) combine to form water (a liquid compound at room temperature). The process of such combination is called a chemical reaction. A chemical reaction involves interactions between the electrons of the atoms, but does not affect the nuclei of the atoms.

In some situations, matter is converted into energy by atomic reactions, also known as nuclear reactions. This type of reaction is fundamentally different from the chemical reaction because it involves changes in the nuclei of atoms. The most common example of an atomic reaction is the hydrogen fusion that occurs inside the sun. The immense pressure inside the sun, and inside other stars, forces atoms of hydrogen together to form atoms of helium. In this process, some of the mass is converted to energy according to the formula=

E = mc 2

Where E is the energy in joules, m is the mass in kilograms, and c is the speed of light, which is approximately 2.99792 x 10 8 meters per second in a vacuum.