Chemistry — Elements & Periodic Table

Henry Moseley proposed the Modern Periodic Law, which states that properties of elements are a periodic function of their atomic numbers.

Group 17 elements (Fluorine, Chlorine, Bromine, Iodine, Astatine) are collectively known as halogens.

Aluminum is the most abundant metal in the Earth's crust, accounting for about 8% of its mass.

Mercury (Hg) is the only metallic element that is liquid at standard room temperature and pressure.

Elements in the same group have the same number of valence electrons, which gives them similar chemical properties.

Argon makes up approximately 0.93% of the Earth's atmosphere, making it the most abundant noble gas.

Iodine is a vital trace element necessary for the production of thyroid hormones, which regulate metabolism.

The Lanthanides are a series of 15 metallic elements ranging from lanthanum to lutetium (57-71), often called rare-earth elements.

Dmitri Mendeleev is widely recognized for arranging elements in a periodic table based on increasing atomic mass and predicting missing elements.

Hydrogen is the first element in the periodic table with an atomic number of 1 and is the lightest gas.

Francium is the most reactive alkali metal, though it is extremely rare and radioactive.

Transuranic elements are chemical elements with atomic numbers greater than 92 (the atomic number of uranium).

Silicon exhibits properties of both metals and non-metals, classifying it as a metalloid.

Group 2 of the periodic table contains the alkaline earth metals, including Beryllium, Magnesium, and Calcium.

Diamonds and graphite are allotropes of the element Carbon.

Noble gases have a complete valence shell, making them inert and stable with an oxidation state of 0.

Sulfur is a core component of Sulfuric acid, which is widely known as the 'King of Chemicals' in the industry.

Atomic radii are commonly expressed in picometers (pm) or Angstroms (Å).

The symbol 'W' stands for Wolfram, which is the German name for Tungsten.

Tungsten (W) has the highest melting point of all metallic elements, making it ideal for high-temperature applications like light bulb filaments.

The elements in Group 16 of the periodic table are known as Chalcogens (ore-formers), which include Oxygen, Sulfur, Selenium, Tellurium, and Polonium.

Atomic radius decreases across a period because the increasing nuclear charge pulls the electron cloud closer to the nucleus.

The f-block elements consist of the Lanthanides and Actinides, which are referred to as inner transition elements as they are placed inside the transition metal block (d-block).

Hydrogen is the simplest and most abundant element in the universe, initially discovered by Henry Cavendish who named it inflammable air.

John Newlands proposed the Law of Octaves in 1864, suggesting that every eighth element exhibits properties similar to the first.

Generally, ionization energy increases across a period, but Boron has a lower ionization energy than Beryllium because the 2p electron in Boron is easier to remove than the 2s electron in Beryllium.

Lithium is the lightest metal and has the lowest density of all solid elements, being about half as dense as water.

The elements in groups 3 through 12 are known as transition elements because they represent the transition between the highly reactive metals of the s-block and the non-metals of the p-block.

Neon gas, when subjected to high voltage in a vacuum tube, emits a characteristic bright red-orange glow.

Group 15 elements are collectively known as Pnictogens, derived from the Greek word 'pnigein' meaning to choke or stifle.

Carbon-12 is the international standard for defining the atomic mass unit (amu), with one-twelfth of its mass being equal to 1 amu.

Metallic character increases down a group; among the alkali metals, Cesium is the most reactive and metallic (excluding the radioactive Francium).

Electron affinity is a measure of the energy change that occurs when an electron is added to an atom to form a negative ion.

Alkali metals (Group 1) have one valence electron, which they readily lose to form ions with a +1 charge.

Transition metals are characterized by their high density, high melting points, ability to form colored compounds, and variable oxidation states.

Mendeleev left gaps in his periodic table for elements yet to be discovered, naming them based on their relationship to known elements (e.g., Eka-aluminium later discovered as Gallium).

Magnesium is the central metal ion in the porphyrin ring of the chlorophyll molecule, which is essential for photosynthesis.

The modern periodic table consists of 7 horizontal rows, which are called periods.

Elements in the s-block and p-block are collectively referred to as representative elements or main-group elements.

Allotropy is the property of some chemical elements to exist in two or more different forms, such as diamond and graphite for carbon.

Group 11 elements, including Copper (Cu), Silver (Ag), and Gold (Au), are traditionally known as coinage metals.

Johann Wolfgang Döbereiner proposed the Law of Triads in 1817, organizing elements into groups of three based on their atomic masses.

Oxygen is the most abundant element in the Earth's crust, accounting for approximately 46.6% by mass.

All elements in a period have the same number of electron shells (principal quantum number n).

Fluoride (a form of fluorine) is commonly added to water and toothpaste to strengthen enamel and prevent cavities.

Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number.

Cerium (Atomic number 58) is the first element of the Lanthanide series (58-71).

Actinides are elements with atomic numbers 89 to 103, where the 5f electron subshell is being filled.