The Mole
This SI unit lets chemists count particles by grouping them into lots of 6.02 × 10²³.
What is the (a) mole?
This positively charged subatomic particle determines the atomic number of an element.
What is a proton?
Elements in the same group of the periodic table have the same number of these outer-shell negatively charged particles.
What are valence electrons?
This type of reaction transfers thermal energy to the surroundings, causing the surroundings to get warmer.
What is an exothermic reaction?
This term describes the change in concentration of a reactant or product per unit time.
What is rate of reaction?
This quantity has units of g mol⁻¹ and links the mass of a substance to the amount in moles.
What is molar mass?
These atoms have the same number of protons but different numbers of neutrons.
What are isotopes?
This type of bonding is the electrostatic attraction between oppositely charged ions.
What is ionic bonding?
This type of enthalpy change is found by burning one mole of a substance completely in oxygen under standard conditions.
What is enthalpy of combustion?
According to collision theory, particles must collide with sufficient energy and this other requirement for a reaction to occur.
What is proper orientation?
This formula gives the simplest whole-number ratio of atoms of each element in a compound.
What is the empirical formula?
This region of space around the nucleus describes where there is a high probability of finding an electron.
What is an orbital?
Across a period from left to right, atomic radius generally decreases because this increases while shielding remains similar.
What is effective nuclear charge? / Zeff
In calorimetry, this equation is used to calculate the thermal energy transferred to or from water.
What is Q=mcΔT
Increasing this variable increases the kinetic energy of particles and increases the proportion of particles with energy greater than the activation energy.
What is temperature?
In a balanced chemical equation, these numbers show the reacting mole ratios between reactants and products.
What are stoichiometric coefficients?
This principle states that electrons fill the lowest available energy orbitals first when writing electron configurations.
What is the Aufbau principle?
According to VSEPR theory, a molecule with four bonding pairs and no lone pairs around the central atom has this shape.
What is tetrahedral?
This law states that the enthalpy change for a reaction is independent of the pathway taken between reactants and products.
What is Hess’s law?
This substance increases the rate of reaction by providing an alternative pathway with a lower activation energy, but is not consumed overall.
What is a catalyst?
A student reacts 2.00 mol of hydrogen with 1.50 mol of oxygen using the equation below. This reactant is in excess.
2H₂ + O₂ → 2H₂O
What is oxygen?
This element has the electron configuration [Ar] 4s¹ 3d⁵, rather than the perhaps-expected [Ar] 4s² 3d⁴.
What is chromium?
This data-booklet model represents bonding as a continuum between ionic, covalent and metallic character, using electronegativity values.
What is the van Arkel-Ketelaar triangle?
In a calorimetry experiment, 100 g of water increases from 10°C to 22°C. Using [c=4.18 J g−1K−1] this is the thermal energy absorbed by the water, to the correct number of sig.figs.
What is 5.02 kJ?
On a graph of product volume against time, the reaction rate at a particular moment is found from this drawn at that point.
What is the gradient of a tangent?