K-electron – K-electron refers to the electrons of an atom with energy quantum number n = 1.
Also known as: K electron

K-shell – K-shell refers to the electrons of an atom with energy quantum number n = 1.
Also known as: K shell

kalium – Kalium is the German name for the element potassium. Kalium is the source of the symbol K for potassium on the periodic table.

Kelvin effect (Thomson effect) – The Kelvin effect is the generation or absorption of heat when an electrical current is passed through a material.

Kelvin temperature scale – The Kelvin temperature scale is an absolute temperature scale based on the definition that the volume of a gas at constant (low) pressure is directly proportional to temperature and that 100 degrees separate the freezing and boiling points of water. Usage: Kelvin temperatures are written with a capital letter ‘K’ and without the degree symbol, such as 1 K, 1120 K. Note that 0 K is ‘absolute zero’ and there are no negative Kelvin temperatures.

keratin – Keratin is a fibrous structural protein found in animal cells and used to form specialized tissues. Specifically, the proteins are only produced by chordates (vertebrates, Amphioxus, and urochordates), which includes mammals, birds, fish, reptiles, and amphibians.
Examples: Hair, nails, horns, bird beaks, and reptile scales are all primarily keratin.

ketal – A ketal is a type of acetal compound with general structure R₂C(OR’)₂ where neither R group is a hydrogen atom. Ketals are a subclass of acetal compounds derived from ketones.

ketene – A ketene is an organic compound containing the >C=O=O functional group. Ketene is also the name for the >C=O=O functional group.
Ketene is also a common name for the compound ethenone. Ethenone is the simplest ketene molecule where R and R’ are both hydrogen atoms.

ketone – A ketone is a compound containing a carbonyl functional group bridging two groups of atoms. The general formula for a ketone is RC(=O)R’ where R and R’ are alkyl or aryl groups. IUPAC ketone functional group names contain “oxo” or “keto”. Ketones are named by changing the -e on the end of the parent alkane name to -one.
Example: Acetone is a ketone. The carbonyl group is connected to the alkane propane, therefore the IUPAC name for acetone would be propanone.

ketoheptose – A ketoheptose is a heptose carbohydrate that contains a ketone functional group.

ketohexose – A ketohexose is a hexose carbohydrate that contains a ketone functional group.

ketopentose – A ketotetrose is a pentose carbohydrate that contains a ketone functional group.

ketose – A ketose is a molecule made up of a monosaccharide bonded to a ketone.

ketotetrose – A ketotetrose is a tetrose carbohydrate that contains a ketone functional group.

ketoxime – A ketoxime is an oxime where neither the R nor R’ functional groups are hydrogen atoms.

kilo – A prefix used on metric units to indicate a multiple of 1000.
Examples: 1 kilogram = 1000 g, 20 kilometers = 20,000 meters.

kilogram (kg) – A kilogram is the basic SI unit of mass. 1 kilogram is 1000 grams.

kilopascal (kPa) – Kilopascal is a unit of pressure. 1 kPa is approximately the pressure exerted by a 10-g mass resting on a 1-cm² area. There are 1,000 pascals in 1 kilopascal. 101.3 kPa = 1 atm.

kinase – A kinase is an enzyme that transfers a phosphate group from one molecule to another substrate.

kindling point – Kindling point is the lowest temperature where a substance will auto-ignite and combust in normal atmospheric conditions without any external influences. Kindling points can change depending on altitude and the partial pressure of oxygen present.
Also known as: autoignition temperature
Example: The kindling point of paper is 451 °F.
Fun Trivia: Fahrenheit 451 by Ray Bradbury was named after the kindling point of paper.

kinetic – A term associated with motion.
An example of usage: The kinetic energy of a particle is equal to ½ multiplied by its mass multiplied by the square of its velocity. Kinetic energy – Kinetic energy is the energy an object possesses due to its motion. An object of mass m moving at velocity v has a kinetic energy equal to ½mv².

kinetic theory – Kinetic theory is a model of molecular motion that is used to explain many of the properties of gases.

kinetics – Kinetics is the study of the rates of chemical reactions.

Klechkowski’s rule – Klechkowski’s rule describes electron configuration and the filling of atomic orbitals. The rule states:
(1) Energy increases with increasing n + l
(2) For identical values of n + l, energy increases with increasing n
The following order for filling orbitals results:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, (8s, 5g, 6f, 7d, 8p, and 9s)
The orbitals listed in parentheses are not occupied in the ground state of the heaviest atom known, Z = 118. The reason orbitals fill this way is because the inner electrons shield the nuclear charge. Orbital penetration is as follows: s > p > d > f.
Also known as: Madelung’s Rule

kosmotropic – Kosmotropic is the ability of a substance to increase the stability of intermolecular forces in water-water interactions, hydrogen bonding, and van der Waals forces.
Kosmotropic agents are compounds that increase protein and polymer stability.
Antonym: chaotropic
Examples: Sulfate, lithium, and zinc ions are kosmotropic. Krypton – Krypton is the name for the noble gas element with atomic number 36 and is represented by the symbol Kr.

kryptonite – Kryptonite is the name of a fictitious element referenced in Superman stories. Kryptonite comes in a variety of colored forms that have different effects on Superman. Kryptonite has nothing to do with the element krypton.