Periodic Classification of Elements and Properties Flashcards

Vocabulary flashcards covering foundational terms, historical laws, modern trends, blocks, and atomic properties from the periodic classification lecture.

Dobereiner's Triads

A classification method proposed by Johann Wolfgang Döbereiner in the early 19th century that grouped chemically similar elements into sets of three, where the atomic mass of the middle element was approximately the average of the other two.

Alkali Metals

Group $1$ elements (such as Lithium, Sodium, and Potassium) having a valency of $+1$ that react to form water-soluble strong bases.

Alkaline Earth Metals

Group $2$ elements (such as Calcium, Strontium, and Barium) having a valency of $+2$ that form bases and are derived from the Earth's crust.

Halogens

Group $17$ non-metallic elements (such as Fluorine, Chlorine, Bromine, and Iodine) with a valency of $-1$ that act as salt producers ('halo' meaning salt, 'genus' meaning producer).

Newlands' Law of Octaves

A historical law of classification stating that when elements are arranged in increasing order of atomic mass, every $8\text{th}$ element exhibits similar properties to the $1\text{st}$, similar to musical octaves (valid only up to Calcium).

Mendeleev's Periodic Law

The principle stating that the properties of elements are periodic functions of their atomic masses, arranged into $8$ groups and $6$ periods while leaving gaps for undiscovered elements.

Modern Periodic Law

The fundamental law stating that the physical and chemical properties of elements are periodic functions of their atomic numbers.

Representative Elements

Elements belonging to Groups $1$, $2$, and $13$ through $18$ that predictably follow standard periodic trends across periods and down groups.

Transition Elements

Elements in Groups $3$ through $12$ (D-block) that represent a transition in properties from metals on the left to non-metals on the right of the periodic table.

Coinage Metals

Specific metals in Groups $11$ and $12$ (such as Copper, Silver, Gold, and Zinc) that were historically used to manufacture coins.

Chalcogens

Group $16$ elements (including Oxygen and Sulphur) named as ore producers ('calco' meaning ore, 'genus' meaning producer).

Lanthanoids

A series of $14$ inner transition elements located at the bottom of the periodic table that follow the element Lanthanum.

Actinoids

A series of $14$ radioactive inner transition elements located at the bottom of the periodic table that follow the element Actinium.

Ionization Energy (Ionization Enthalpy)

The amount of energy required to remove the most loosely bound electron from an isolated gaseous atom in its ground state.

Nuclear Charge

The net positive charge exerted by protons in the nucleus on surrounding electrons, which increases relatively as electrons are lost.

Shielding Effect

The electrostatic repulsion exerted by inner-shell electrons on outer valence electrons, reducing the attractive force of the nucleus on valence electrons.

Penetration Effect

The proximity and attractive pull of subshell electrons towards the nucleus, following the efficiency order $s > p > d > f$.

Electron Gain Enthalpy

The energy change (released or absorbed) that occurs when an electron is added to a neutral isolated gaseous atom to form a negative ion (anion).

Electronegativity

A relative scale measurement (ranging from $0$ to $5$ on the Pauling scale) of an atom's propensity to attract bonding or gained electrons.

S-block Elements

Elements in Groups $1$ and $2$ whose last electron enters the $s$ subshell, having a valence shell configuration of $ns^{1-2}$.

P-block Elements

Elements in Groups $13$ through $18$ whose last electron enters the $p$ subshell, having a valence shell configuration of $ns^2 np^{1-6}$.

D-block Elements

Elements in Groups $3$ through $12$ whose last electron enters the penultimate $(n-1)d$ subshell, having a general electronic configuration of $(n-1)d^{1-10} ns^{1-2}$.

F-block Elements

Elements whose last electron enters the anti-penultimate $(n-2)f$ subshell, possessing a general electronic configuration of $(n-2)f^{1-14} (n-1)d^{0-1} ns^2$.

Covalent Radius

Half the distance between the centers of two identical nuclei connected by a single covalent bond.

Van der Waals Radius

Half the distance between the nuclei of two non-bonded adjacent identical atoms in the solid state, commonly measured for noble gases.