Chapter 5, Section 3

Electron Configuration and Periodic Properties

Atomic Radii

-You can express an atom's radius is to measure the distance between the nuclei of two identical atoms that are chemically bonded together, then divide this distance by two.

- The atomic radius may be defined as one-half the distance between the nuclei of identical atoms that are bonded together.

Period Trends

- The trend to smaller atoms across a period is caused by the increasing positive charge of the nucleus.

Group Trends

- In general, the atomic radii of the main-group elements increase down a group.

Ionization Energy

In general, ionization energies of the main group elements increase across each period. Its increased by the nuclear charge. When the charge is higher it attracts more electrons. Among the main group elements, ionization energies generally decrease down the groups. Electrons are removed more easily. More electrons lie between the nucleus and the electrons in the highest level.


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Electron Affinity

The energy change that occurs when an electron is acquired by a neutral atom. The halogens gain more electrons. The d sublevel increase the nuclear charge and then more negative. They add more difficulty down the groups. Increase in effective nuclear charge down and makes electron affinities increase. An increase in atomic radius down a group, and which decreases electron affinities. They tend to be the same size.


Ionic Radii

- A positive ion is known as a cation.

- A negative ion is known as an anion.

Period Trends

- Metals at the left tend to form cations and the nonmetals at the upper right tend to form anions.

- Cationic radii decrease across a period because the electron cloud shrinks due to the increasing nuclear charge acting on the electrons in the same main energy idea.

Group Trends

-Outer electrons in both cations and anions are in higher energy levels as one reads down a group.

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Valence Electrons

-Electrons available to be lost, gained, or shared in the formation of chemical compounds are called valance electrons.


- Valance electrons are most commonly found in incompletely filled main-energy levels.

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Electronegativity

Is a measure to the ability of an atom in a chemical compound to attract electrons from another atom in the compound. Electronegativities tend to increase across each period, although there are exceptions. Electronegativities tend to either decrease down a group or remain about the same.


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Periodic Properties of the d- and f-Block Elements

-Elements in d-block are all metals.


Atomic Radii

- d-block elements generally decrease across the periods.

- the decrease is less than that for the main-group elements because of the extra electrons in the sublevel.

-The f-block elements are located between lanthanum and hafnium.

-There is a great increase in atomic number when you hit the f-block elements.

Ionization Energy

- The energy in both blocks increase across the periods.

- This happens because there are electrons available for ionization in the outer s sublevels are less shielded from the increasing nuclear charge by electrons in the incomplete sublevels.

Ion Formation and Ionic Radii

- electrons in the highest occupied sublevel are always removed first.

- THis means that although newly added electrons occupy the d-sublevels.

Electronegativity

-The d-block elements also follow the general trend for electronegativity values to increase as radii decrease, and vice versa.

- The f-block elements all have similar electronegativities.

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