http://www.ck12.org Chapter 6. The Periodic Table
6.3 Trends in the Periodic Table
Lesson Objectives
- Describe what a noble gas configuration is and explain how elements react by losing, gaining, or sharing
electrons to achieve a noble gas configuration. - Define cation and anion, and explain the relationship between the number of electrons typically lost for a
particular element and its position on the periodic table. - Describe how ions are formed, and explain why it is easier to remove valence electrons than core electrons.
- Define atomic radius and describe the trend of atomic radius across a period and down a group of the periodic
table. - Define ionic radius and describe how and why ionic radius differs for cations and anions. Describe the trends
in ionic radius. - Define ionization energy and describe how and why ionization energy differs for cations and anions. Describe
the trend in ionization energy across a period and down a group of the periodic table.
Lesson Vocabulary
- atomic radius: The distance from an atom’s nucleus to the electrons in the outermost orbitals.
- ion: An atom or group of bonded atoms that has a positive or negative charge.
- cation: A positively charged ion.
- anion: A negatively charged ion.
- ionization energy: The energy required to remove an electron from an atom.
- electron shielding: When outer electrons are partially shielded from the attractive force of the protons in the
nucleus by inner electrons. - isoelectronic: Two atoms or ions with the same number number of electrons and therefore the same electron
configurations. - electron affinity: The amount of energy required for an electron to be added to a neutral atom in gas form.
- ionic radius: A measure of the size of an atom that is helpful in comparing the size of an ion to that of the
parent atom. - electronegativity: A measure of the ability of an atom to attract shared electrons when the atom is part of a
compound. - metal: An element that is a good conductor of heat and electricity.
- nonmetal: An element that is generally a poor conductor of heat and electricity.
- metalloid: An element with properties that are intermediate between those of metals and nonmetals.
Check Your Understanding
- Write the electron configurations for the following atoms:
a. Xe