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Why Successive Electronic Affinities Have Negative Values
A student recently asked me why successive electron affinities can have negative values. Here’s a quick explanation: First, let’s clarify what we mean by successive electron affinity. It refers to the energy change when adding a second, third, or subsequent electron to an already negatively charged ion, after one electron has been added to the…
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Ionization Energy across a Period: Trends & Anomalies Explained
Generally, ionization energy increases across a period from left to right. If you need a quick refresher, here’s why: As you move across a period, the nuclear charge increases, but the number of energy levels stays the same. At the same time, the atomic size decreases, pulling the electrons closer to the nucleus. Because the…
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Does atomic radius increase from left to right? (Answer & Explanation for Degree Students)
Answer No. Atomic radii DECREASE as we move from left to right across a period in the periodic table. The table below, for example, shows the atomic radii of Period 3 elements—you can observe a steady decrease from sodium (Na) to argon (Ar) through magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), and…
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Bragg Slater Radii
In the previous section, we saw that since the exact size of an atom is difficult to determine, chemists use different types of atomic radii—such as covalent, van der Waals, ionic, and metallic radii—each defined according to the type of bonding involved. There is also the Bragg–Slater radius, which provides another way to estimate atomic…
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Atomic Radii vs Metallic Radii
The term atomic radius generally refers to the distance from the center of an atom’s nucleus to the outermost shell of its electrons. However, determining the exact size of an atom is challenging because atoms do not have sharply defined boundaries. Moreover, it’s impossible to isolate a single atom and measure its radius directly. Therefore,…
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Beehive Shelf: Uses, Features, & Safety
When collecting gas by the displacement method—commonly used for gases that are insoluble or only slightly soluble in water—you typically need a gas jar that is placed inverted in water, as shown in the setup above. This arrangement allows the gas from the delivery tube to rise and displace the water inside the jar. To…
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Gas Jar: Features, Uses, Types, & Safety
Many chemistry experiments involve the release of gases. While some gases can be safely vented through fume hoods or into well-ventilated areas, there are situations where certain gases need to be collected. In such cases, gas jars are used. The primary role of a gas jar in the laboratory, therefore, is to collect and temporarily…
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Pressure-Equalizing Dropping Funnel: Features, Uses, & Safety
When working in closed systems where pressure changes can cause problems, the most suitable laboratory equipment for adding controlled amounts of liquid to a reaction flask is not a standard dropping funnel, but a pressure-equalizing dropping funnel (also called a dropping funnel with pressure-equalizing capabilities). As shown in the diagram above, a pressure-equalizing dropping funnel…
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What Are Laboratory Squeeze Bottles?
Many students get confused when they are asked to use a laboratory squeeze bottle in their experiments. They often think it is a completely different piece of equipment from the wash bottle they already know. In reality, laboratory squeeze bottles and wash bottles are the same type of container—just known by different names. The term…
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Conical Flask: Features, Uses, & Types
What is a Conical Flask? A conical flask, also known as an Erlenmeyer flask, is a type of laboratory glassware with a wide, flat base that tapers into a narrow neck. This flask is widely used in chemistry and biology laboratories for mixing solutions, heating liquids, titrations, and culturing microorganisms. Main Features The conical flask…
