627 articles
All articles — Page 19
Every article in the chemistry library, newest first.
Which Elements Are Liquid at Room Temperature?
Only two elements — mercury and bromine — are liquid at standard room temperature. Here's why, plus the four metals that melt on a hot day and what makes each of them unusual.
What Are Heavy Metals? Meaning, Examples and Why the Term Is Confusing
What 'heavy metals' means in chemistry, toxicology and the news, the elements usually included (lead, mercury, cadmium, arsenic), how they affect health, and why chemists find the term unhelpful.
The Carbon Group (Group 14): Carbon, Silicon, Germanium, Tin and Lead
Group 14 runs from a nonmetal to metalloids to metals. How carbon, silicon, germanium, tin and lead compare, why carbon is the basis of life and silicon of electronics, and the trend toward +2 oxidation states.
What Is the Most Electronegative Element? Fluorine and the Top 10
Why fluorine is the most electronegative element, the top 10 ranked on the Pauling scale, the least electronegative elements, and what electronegativity means for bonding.
Density in Chemistry: Formula, Units and Worked Examples
What density is, how to calculate it and rearrange the formula, unit conversions, density of gases, and how density identifies substances — with worked examples.
The Nitrogen Group (Group 15): Nitrogen, Phosphorus, Arsenic, Antimony and Bismuth
Group 15, the pnictogens: how nitrogen, phosphorus, arsenic, antimony and bismuth change from gas to metal, the nitrogen cycle, phosphorus in DNA and fertilizers, and arsenic's toxic history.
Which Elements Are Radioactive? The Complete List
Every element from 84 (polonium) upward is radioactive, plus technetium and promethium. Here's the full list, why some elements have no stable isotopes, and which radioactive elements you meet every day.
The s, p, d and f Blocks of the Periodic Table Explained
Why the periodic table is divided into s, p, d and f blocks, how block widths come from orbital capacities, how to read electron configurations straight off the table, and why the f-block sits underneath.
Limiting Reagent: How to Find It (With Worked Examples)
What a limiting reagent is, the reliable method for finding it, how to calculate theoretical yield and leftover excess reactant, and why the smallest mass isn't always limiting.
The Halogens: Fluorine, Chlorine, Bromine, Iodine and Beyond
Group 17 explained: why the halogens are so reactive, how their colour, state and reactivity change down the group, displacement reactions, and their uses from water treatment to medicine.
Element Symbols That Don't Match Their Names (and Why)
Why sodium is Na, iron is Fe, gold is Au and lead is Pb: the full list of element symbols that come from Latin, Greek and German names, with memory tips for each.
How to Draw Lewis Dot Structures: A Step-by-Step Guide
A reliable step-by-step method for drawing Lewis structures, worked examples from water to carbon dioxide and nitrate, formal charge, resonance, and the exceptions to the octet rule.
Electron Configuration Exceptions: Why Chromium and Copper Break the Rules
Why chromium is [Ar] 4s1 3d5 and copper is [Ar] 4s1 3d10, the stability of half-filled and filled d subshells, the full list of common exceptions, and why the heavier elements have even more.
Percent Composition: How to Calculate It and What It Tells You
How to find the mass percent of each element in a compound, worked examples from water to caffeine, and how chemists use percent composition in the real world.
The Noble Gases: Why Group 18 Is (Almost) Unreactive
Helium, neon, argon, krypton, xenon and radon: their full electron shells, properties and trends, how they were discovered, the surprise of noble gas compounds, and their uses.
The Most Abundant Elements in the Universe (and Where They Came From)
Hydrogen and helium make up about 98% of ordinary matter. Here are the most abundant elements in the universe ranked, and how the Big Bang, stars and supernovae made them.
How to Find Oxidation Numbers: Rules and Worked Examples
The oxidation number rules in priority order, worked examples from simple salts to polyatomic ions, and how to handle peroxides, hydrides and fractional oxidation states.
Intermolecular Forces: London Dispersion, Dipole-Dipole and Hydrogen Bonds
The forces between molecules explained — London dispersion, dipole-dipole and hydrogen bonding — how to rank them, and how they control boiling points, solubility and viscosity.
Electron Affinity: Definition, Trend and Why Chlorine Beats Fluorine
What electron affinity measures, the sign convention that confuses everyone, the periodic trend, why chlorine has a higher electron affinity than fluorine, and which elements don't want an extra electron.
Percent Yield Explained: Theoretical vs. Actual Yield
How to calculate theoretical yield and percent yield, worked examples, why real yields fall short of 100%, and what it means when a yield comes out above 100%.
Transition Metals: Properties, Colours and Why They Matter
What makes the d-block transition metals special: variable oxidation states, coloured compounds, catalysis and magnetism — with examples from iron, copper, chromium and titanium.
What Is the Best Conductor of Electricity? Silver, Copper and Gold Compared
Silver is the best electrical conductor of all the elements, but copper does most of the work. Here's why, how conductivity is measured, and where aluminium and gold fit in.
How to Balance Chemical Equations: A Step-by-Step Method
Why equations must balance, a reliable inspection method with worked examples, tricks for combustion and polyatomic ions, and how the algebraic method handles hard cases.
How to Name Ionic Compounds (With Transition Metals and Polyatomic Ions)
The rules for naming ionic compounds, Roman numerals for transition metals, polyatomic ions, acids and hydrates — and how to write the formula from the name.
Periodic Trends Explained: The Two Ideas Behind Every Pattern
Atomic radius, ionization energy, electronegativity, electron affinity and metallic character all follow from two ideas: effective nuclear charge and shielding. Here's how, with a one-page summary.
Molarity Explained: How to Calculate Concentration and Make Solutions
What molarity means, how to calculate it, how to make a solution of a given concentration in the lab, and how dilution with C₁V₁ = C₂V₂ works.
The Chalcogens (Group 16): Oxygen, Sulfur, Selenium, Tellurium and Polonium
Group 16 explained: why oxygen is so reactive, sulfur's many forms and uses, selenium's role in the body and electronics, tellurium's rarity, and polonium's radioactive history.
Semiconductors Explained: Why Silicon Runs the Modern World
What makes silicon and germanium semiconductors, band gaps in plain language, how doping with phosphorus and boron creates n-type and p-type material, and how that builds diodes, transistors, LEDs and solar cells.
Nuclear Fission vs. Fusion: What's the Difference?
How fission splits heavy nuclei and fusion joins light ones, why both release energy, the binding energy curve and iron-56, chain reactions, and why fusion power is so hard.
Solubility Rules: How to Predict Precipitates
The solubility rules for ionic compounds in water, a memory aid, how to use them to predict precipitation reactions, and how to write net ionic equations.