Understanding Periodic Table Trends

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Discussion Overview

The discussion focuses on understanding periodic table trends, including concepts such as effective nuclear charge, atomic size, ionization energies, electron affinity, and reactivity. Participants explore these trends in the context of chemistry, particularly for educational purposes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • Some participants describe effective nuclear charge (Z effective) as the atomic number minus the number of core electrons, noting that Z increases across a row and remains relatively constant down a group.
  • It is mentioned that atomic radius decreases from left to right across a period and increases down a group.
  • Participants state that ionization energies increase from left to right and from bottom to top of a group.
  • Electron affinity is discussed as becoming increasingly negative from left to right, with some suggesting it does not change significantly down a group but may become more negative going up a group.
  • Reactivity trends are proposed, indicating that reactivity decreases from left to right due to increasing ionization energies and increases down a group as ionization energies decrease.
  • One participant reiterates the definition of atomic number (Z) and its relationship to protons and electrons, emphasizing the role of outermost electrons in determining chemical properties.
  • Another participant raises a question about the divergence of atomic mass (A) and atomic number (Z) as elements become larger.

Areas of Agreement / Disagreement

Participants present multiple viewpoints on the trends in the periodic table, with some concepts being reiterated and others questioned. The discussion does not reach a consensus on all points, particularly regarding the implications of atomic mass and atomic number divergence.

Contextual Notes

Some statements rely on specific definitions and assumptions about atomic structure and periodicity, which may not be universally agreed upon. The discussion includes references to external resources for further study.

StephenDoty
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Hello everyone. I am currently studying the periodic trends in my chemistry I class. So I just want to make sure I understand the concepts.

Z effective= Atomic # - # of core electrons.
Z increases across a row and doesn't really change going down a group.

Size, radius, of atoms
the radius decrease from left to right and increase going down a group.

Ionization energies
Increases from left to right and from bottom to top of a group

electron affinity
becomes increasingly negative going from left to right and doesn't really change going down a group but can become increasingly negative going up a group

Reactivity
decreases going from left to right since ionization energies increase going left to right
and increases going down a group since ionization energies decrease going down a group.
 
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Z (atomic number) represents the number of protons (and + charges) in the nucleus of an atom, and in a neutral atom there is a equal number of electrons surrouding the nucleus. It is the electrons in the outermost 'shells' of the atom, i.e. those electrons that are most weakly bound, that determine the chemical properties of the atom (element).

Atomic mass is related to the total number of nucleons (protons and neutrons) in the nucleus of an atom. The atomic mass does not equal the mass of an equivalent number of nucleons because nucleons give up some energy (binding energy) when they combine to form more complex nuclei.

In the standard periodic table, Z increases from left to right, and from top to bottom.

This is a really good site for studying the periodicty of properties of the elements:
http://www.webelements.com/
http://www.webelements.com/periodicity/

e.g. http://www.webelements.com/periodicity/electron_affinity/

http://www.webelements.com/periodicity/atomic_radius/
 
do the chapter 23 Thermochemistry
 
Astronuc said:
Z (atomic number) represents the number of protons (and + charges) in the nucleus of an atom, and in a neutral atom there is a equal number of electrons surrouding the nucleus. It is the electrons in the outermost 'shells' of the atom, i.e. those electrons that are most weakly bound, that determine the chemical properties of the atom (element).

Atomic mass is related to the total number of nucleons (protons and neutrons) in the nucleus of an atom. The atomic mass does not equal the mass of an equivalent number of nucleons because nucleons give up some energy (binding energy) when they combine to form more complex nuclei.

In the standard periodic table, Z increases from left to right, and from top to bottom.

This is a really good site for studying the periodicty of properties of the elements:
http://www.webelements.com/
http://www.webelements.com/periodicity/

e.g. http://www.webelements.com/periodicity/electron_affinity/

http://www.webelements.com/periodicity/atomic_radius/


nuc

Why does A and Z diverge as the elements get bigger?
 

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