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The Changing States of Solids, Liquids, and Gases

When a substance goes from one state of matter — solid, liquid, or gas — to another state of matter, the process is a change of state. Some rather interesting things occur during this process. [more…]

How Would You Define Chemistry as a Science?

Chemistry is a branch of science that studies the composition and properties of matter and the changes it undergoes. Chemistry is far more than a collection of facts and a body of knowledge. It’s all about [more…]

What Chemists Do and Where They Work

Most chemists operate in two worlds of work. One is the macroscopic world that you see, feel, and touch. Chemists also operate in the microscopic world that you can’t directly see, feel, or touch. [more…]

How to Distinguish Pure Substances and Mixtures

Chemists can classify matter as solid, liquid, or gas. But there are other ways to classify matter, as well — such as pure substances and mixtures. Classification is one of the basic processes in science [more…]

How Scientists Measure Matter

Scientists are often called on to make measurements of matter, which may include such things as mass (weight), volume, and temperature. A worldwide measurement system has been adopted to ensure that scientists [more…]

The Properties of Chemical Substances

When chemists study chemical substances, they examine two types of properties: chemical properties and physical properties. Some physical properties are [more…]

What Are the Different Types of Energy?

Energy can take several forms — such as heat energy, light energy, electrical energy, and mechanical energy. But two general types of energy are especially important to chemists: kinetic energy and potential [more…]

How Is Energy Measured?

You can measure kinetic energy (energy of motion) with a thermometer. Measuring potential (stored) energy can be a difficult task. The potential energy of a ball stuck up in a tree is related to the mass [more…]

The Nucleus: The Center of an Atom

The nucleus, that dense central core of the atom, contains both protons and neutrons. Electrons are outside the nucleus in energy levels. Protons have a positive charge, neutrons have no charge, and electrons [more…]

Atomic Structure: The Bohr Model

There are two models of atomic structure in use today: the Bohr model and the quantum mechanical model. Of these two models, the Bohr model is simpler and relatively easy to understand. [more…]

Atomic Structure: The Quantum Mechanical Model

Two models of atomic structure are in use today: the Bohr model and the quantum mechanical model. The quantum mechanical model is based on mathematics. Although it is more difficult to understand than [more…]

How to Represent Electrons in an Energy Level Diagram

Chemists sometimes use an energy level diagram to represent electrons when they’re looking at chemical reactions and bonding. An energy level diagram is more useful and easier to work with than quantum [more…]

How to Depict Electrons in Electron Configuration Notation

Chemists use electron configuration notation to depict electrons in chemical reactions and bonding. Electron configuration notation is easier to use than the quantum mechanical model. [more…]

Why Are Valence Electrons Important?

Valence electrons are the electrons in the outermost energy level of an atom — in the energy level that is farthest away from the nucleus. When chemists study chemical reactions, they study the transfer [more…]

Isotopes: Different Types of Atoms

Atoms in a chemical element that have different numbers of neutrons than protons and electrons are called isotopes. The atoms in a particular element have an identical number of protons and electrons but [more…]

Ions: Atoms with an Electrical Charge

Atoms (or groups of atoms) in which there are unequal numbers of protons and electrons are called ions. Usually, the number of protons and electrons in atoms are equal. But there are cases in which an [more…]

The Periodic Table: Families and Periods

In the periodic table of elements, there are seven horizontal rows of elements called periods. The vertical columns of elements are called groups, or families [more…]

Radioactivity and Man-Made Radioactive Decay

Radioactivity is the spontaneous decay of an unstable nucleus. An unstable nucleus may break apart into two or more other particles with the release of some energy. This breaking apart can occur in a number [more…]

The Process of Natural Radioactive Decay

Certain naturally occurring radioactive isotopes are unstable: Their nucleus breaks apart, undergoing nuclear decay. Sometimes the product of that nuclear decay is unstable itself and undergoes nuclear [more…]

Nuclear Chemistry: Half-Lives and Radioactive Dating

Scientists look at half-life decay rates of radioactive isotopes to estimate when a particular atom might decay. A useful application of half-lives is [more…]

The Basics of Nuclear Fission

Nuclear fission occurs when a larger isotope breaks apart into two or more elements. Scientists usually accomplish this task (for some controlled nuclear reactions) by bombarding a large isotope with a [more…]

Nuclear Fusion: The Hope for Our Energy Future

Nuclear fusion is essentially the opposite of nuclear fission. In fission, a heavy nucleus is split into smaller nuclei. With fusion, lighter nuclei are fused into a heavier nucleus. [more…]

What Are the Effects of Radiation and Radon?

Radiation can destroy tissue and ionize and fragment cells. Radon is a radioactive isotope that has been linked to increased instances of lung cancer. Radon-222 is formed naturally as part of the decay [more…]

Ionic Bonds: Why and How Ions Are Formed

Ionic bonding is the type of bonding that holds salts together. To better understand why and how ions — atoms that have a charge due to the loss or gain of electrons — are formed, you can study what happens [more…]

Positive and Negative Ions: Cations and Anions

Cations (positively-charged ions) and anions(negatively-charged ions) are formed when a metal loses electrons, and a nonmetal gains those electrons. The electrostatic attraction between the positives and [more…]

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