Language of Chemistry, Valency, and Chemical Equations

Vocabulary flashcards covering the language of chemistry, atomic symbols, valency, ions, radicals, writing chemical formulas, chemical equations, and the law of conservation of matter.

Symbol

The short form or abbreviated name of an element that represents a specific element or one atom of an element (e.g., the symbol '$H$' represents one atom of the element hydrogen).

Valency

The number of hydrogen atoms which can combine with [or displace] one atom of the element [or radical] forming a compound (e.g., in water [$H_2O$], two atoms of hydrogen combine with one atom of oxygen, so the valency of oxygen is $2$).

Variable Valency

The ability of certain elements to exhibit more than one valency (e.g., copper exhibiting $Cu^{1+}$ and $Cu^{2+}$, or iron exhibiting $Fe^{2+}$ and $Fe^{3+}$).

Ion

Any atom or group of atoms carrying a positive or negative charge due to the loss or gain of electrons.

Cation

A positively charged ion formed due to the loss of electrons (e.g., potassium ion [$K^{1+}$] or sodium ion [$Na^{1+}$]).

Anion

A negatively charged ion formed due to the gain of electrons (e.g., oxide ion [$O^{2-}$] or chloride ion [$Cl^{1-}$]).

Radical

A group of atoms of elements that behave like a single unit and show valency, which can be positive (e.g., ammonium [$NH_4^{1+}$]) or negative (e.g., sulphate [$SO_4^{2-}$], bicarbonate [$HCO_3^{1-}$]).

Chemical Formula

The representation of a substance by means of symbols that denotes the number of atoms of each element present in a compound (e.g., potassium nitrate is $KNO_3$, containing $1$ atom of $K$, $1$ atom of $N$, and $3$ atoms of $O$).

Chemical Equation

A shorthand form representing the result of a chemical change using the symbols and chemical formulas of the reacting substances and products.

Reactants

The substances taking part in a chemical reaction, written on the left-hand side of a chemical equation (e.g., zinc and dilute sulphuric acid in $Zn + H_2SO_4 \rightarrow ZnSO_4 + H_2$).

Products

The substances formed as a result of a chemical reaction, written on the right-hand side of a chemical equation (e.g., magnesium sulphate and hydrogen gas in $Mg + H_2SO_4 \rightarrow MgSO_4 + H_2$).

Balanced Equation

A chemical equation in which the number of atoms of each element of the reactants is equal to the number of atoms of each element of the products (e.g., $2Mg + O_2 \rightarrow 2MgO$).

Unbalanced Equation

A chemical equation in which the number of atoms of each element of the reactants is not equal to the number of atoms of each element of the products (e.g., $Zn + HCl \rightarrow ZnCl_2 + H_2$).

Law of Conservation of Matter

The scientific law stating that in the course of a chemical reaction matter is neither created nor destroyed during the chemical change, meaning the total mass of the reactants is equal to the total mass of the products.

Hit & Trial Method

A step-by-step balancing method where coefficients are adjusted by inspecting and balancing atoms of each element sequentially across reactants and products until both sides are equal.

Nitric Oxide

The common chemical name for nitrogen monoxide, represented by the molecular formula $NO$.

Nitrous Oxide

The common chemical name for dinitrogen oxide, represented by the molecular formula $N_2O$.

Divalent Metal

A metal that possesses a valency of $2$ (or forms a $2+$ cation), such as calcium ($Ca^{2+}$), iron ($Fe^{2+}$), copper ($Cu^{2+}$), magnesium ($Mg^{2+}$), and zinc ($Zn^{2+}$).

Limitations of Chemical Equations

Details that a basic chemical equation does not inherently reveal without extra notation, including physical states, reaction conditions (temperature, pressure, catalyst), concentration, reaction speed, accompanying heat changes, and reaction completion.

Interchanging Valencies Method

The step-by-step method of writing chemical formulas where symbols are written with their valencies, the signs are ignored, and the valency numbers are cross-transposed to the lower right of each counterpart, using brackets for compound radicals when the subscript is $2$ or greater.

Aluminate Radical

A monovalent negative radical consisting of aluminium and oxygen, represented by the symbol and charge $AlO_2^{1-}$.

Zincate Radical

A divalent negative radical represented by the symbol and charge $ZnO_2^{2-}$.

Plumbite Radical

A divalent negative radical represented by the symbol and charge $PbO_2^{2-}$.

Dichromate Radical

A divalent negative radical represented by the symbol and charge $Cr_2O_7^{2-}$.

Noble Gas

An element with a stable electronic configuration and a valency of $0$ (e.g., helium with atomic number $2$, neon with electronic configuration $2,8$, and argon with $2,8,8$ in the first 20 elements).

Metalloid

An element exhibiting properties between metals and non-metals, exemplified in the first $20$ elements by boron (atomic number $5$, valency $+3$) and silicon (atomic number $14$, valency $4$).