Chem Notes Ch 2 Flashcards
Group
Elements that occupy the same column and have the same number of valance electrons.
Period
Elements that occupy the same row and have the same number of electron shells
Group 1 Elements (excluding hydrogen)
Alkali Metals
Group 2 Elements
Alkaline Earth Metals
Groups 3-12 Elements:
Transition Metals
Groups 13-17 Elements
Metalloids, which have a combination of both metallic and non-metallic characteristics.
Group 17 Elements
Halogens
Group 18 Elements
Noble Gases
Period 6 elements
Lanthanides
Period 7 elements
Actinides
Diatomic atoms
Hydrogen, Nitrogen, Fluorine,
Oxygen, Iodine, Chlorine, and Bromine. Have No Fear Of Ice Cold Beer
Metallic character on periodic table trend
Increases going from right to left across a period and increases going down a group
Properties of metals
Malleable, lustrous, good conductors of electricity/heat, forms basic oxides, lose electrons to form cations, usually solid at room temperature with exception of Hg liquid, high melting point, high boiling point
Properties of non-metals
Brittle, dull, poor conductors of electricity/heat, form of acidic oxides, gain electrons to form anions, gas or solid at room temperature with exception of Br liquid, low melting point, low boiling point
Atomic radius definition
Half the distance between the nuclei of two identical atoms bonded together
Atomic radius trend
Decreases from left to right across a period and increases going down a group.
Effective nuclear charge (Zeff) definition
Nuclear charge experienced by an electron in an atom with multiple electrons. This charge is assigned due to a shielding
effect of electrons preventing electrons in higher orbitals from experiencing a strong attraction to the nucleus. Explains why valence electrons are more easily removed.
Zeff = Number of protons - Number of shielding electrons
Effective nuclear charge (Zeff) trend
Increases across a period from left to right and decreases going down a group. Across a period, numbers of protons increase with no increase in shielding effect, which results in electrons being pulled closer to the nucleus due to a
stronger attraction. Going down a group, more shielding causes Zeff to decrease.
When a neutral atom loses an electron
Becomes a cation. Radius will decrease due to an increase in Zeff, causing increase in protons pulling the electrons closer to the nucleus.
Metals form cations, resulting in their ionic radius to be less than their atomic radius.
When a neutral atom gains an electron
Becomes an anion. Radius will increase due to a decrease in Zeff, causing a decrease in protons pulling the electrons to the nucleus.
Non-metals form anions, resulting in their ionic radius to be greater than their atomic radius.
Isoelectronic Series definition
Atoms that have the same electron configuration, but differing numbers of protons. The most positively charged atom will have the smallest radius
Ionization energy definition
The energy needed to remove an electron from an atom
Ionization energy Trend
Increases going from left to right across a period and
decreases down a group, because of Zeff trend.
Multiple Ionization Energies
The first ionization energy is the energy required to
remove the outermost electron. Following removal of the first electron, elements can have second, third, fourth, etc. ionization energies. These values are always larger than
the first ionization energy because subsequent electrons are more difficult to remove.
2 exceptions to the rules for ionization energy
- Alkaline earth metals have greater ionization energy than group 13 elements because alkaline earth metals have completely filled orbitals
- Group 15 elements have greater ionization energy than
group 16 elements. Group 15 elements have half-filled orbitals
Electron Affinity definition
Amount of energy released when an electron is added to an atom
Electron Affinity trend
Increases from left to right across a period and decreases down a group. Going across a period, greater nuclear attraction between protons and electrons creates a stronger affinity for electrons. Going down a group, the attraction of an electron to the nucleus decreases due to shielding.
Note: Similar to ionization energy, the trend for electron affinity is a general trend and may not apply to all elements in the periodic table. For example, although phosphorous is to the right of silicon, phosphorous has a half-filled subshell electron configuration. Silicon has a
greater affinity for an electron than phosphorous because accepting an electron will give it the half-filled subshell configuration.
Electronegativity definition
Ability of an atom to attract electrons in a bond. The higher the electronegativity of an atom, the greater ability to attract an electron pair
Electronegativity trend
increases going from left to right across a period and decreases down a group. The most electronegative element is fluorine
Noble gases are an exception to this trend as they have full valence shells and no electronegativity value.
