Periodic Properties of Elements

Development and Organization of the Periodic Table

• Dmitri Mendeleev, a Russian chemist, created a periodic table arranging 65 elements by atomic mass, predicting properties of undiscovered elements.
• Julius Lothar Meyer, a German chemist, independently arrived at a similar periodic organization focusing on physical properties.
• Modern periodic table aligns elements by atomic number, a change credited to Henry Moseley, an English physicist.

Trends in the Periodic Table

• The periodic law states that elements exhibit periodic recurrence of similar properties when arranged by atomic number.
• Groups: Vertical columns in the periodic table with elements sharing similar properties, indicated by group numbers.
• Periods: Horizontal rows where all elements share the same highest principal quantum number, numbered from left to right.

Main-Group Elements

• S-block includes alkali metals (Group 1) and alkaline earth metals (Group 2).
• P-block consists of chalcogens (Group 16), halogens (Group 17), and noble gases (Group 18).
• D-block elements are known as transition metals; f-block elements, including lanthanides and actinides, are placed below the main table.

Trends in Atomic Size

• Atomic size is defined by the distance between adjacent atomic nuclei, typically halved for measurement.
• The metallic radius applies to metals; covalent radius is for nonmetals.
• Atomic size increases down a group due to higher principal quantum numbers, while it decreases across a period due to increased effective nuclear charge.

Trends in Ionization Energy

• Ionization energy (IE) is the energy needed to remove one mole of electrons from gaseous atoms or ions, generally positive due to the attraction between nucleus and electrons.
• First ionization energy (IE1) removes the outermost electron; successive ionization energies (IE2, IE3, etc.) require more energy.
• Ionization energies decrease with increasing atomic size.

Trends in Electron Affinity

• Electron affinity (EA) measures energy change when adding an electron to an atom, typically negative for the first addition.
• Group 17 elements tend to exhibit large negative electron affinities, while EA2 is always positive due to repulsion when adding a second electron.
• Noble gases have minimal electron affinity as they require energy to enter the next shell.

Trends in Electronegativity

• Electronegativity (EN) measures an atom's ability to attract electrons in a bond.
• EN increases left to right across a period due to higher nuclear charge and decreases top to bottom in a group due to greater distance from the nucleus.

Trends in Metallic Character

• Metals have few electrons in their outer shell, can easily lose electrons to form cations, exhibit conductivity, and are malleable.
• Nonmetals tend to gain electrons, forming anions, and are generally poor conductors.
• Metallic character decreases across a period and increases down a group, linked to atomic size and shell number.

Magnetic Properties

• Magnetic behavior of atoms and ions is influenced by their electron configurations.
• Diamagnetic substances have paired electrons, resulting in cancelled magnetic effects.

Explore the development and organization of the periodic table with insights into atomic structure and reactivity. This quiz covers key trends as identified by Dmitri Mendeleev and summarizes their behavior. Test your knowledge on how elements are organized and their recurring characteristics.