Chem 101 Unit 4: Electron Behavior

Valence electrons

electrons in the high energy, outermost shell of an atom (usually can be determined by the electrons in the highest energy level but isn’t always so cut and dry for example titanium has 4 valence electrons with an electron config of [Ar]4s²3d²)

Core electrons

any electrons that aren’t valence

ion

a charged atom/molecule

Cation

an ion with fewer electrons, it has more protons than electrons

Anion

an ion with more electrons, it has less protons than electrons

isoelectronic

atoms with the same number of electrons but different number of protons, often called isoelectronic species (a set of isoelectronic species is an isoelectronic series)

How do you determine the bigger atom in an isoelectronic series?

The more negative the charge the bigger the ionic radius because the electrons are repelling each other more in the electron cloud.

quantum numbers

coordinates for an electron used to describe the distribution of electron density in an atom (however you never know exactly where an electron is)

n

principle quantum number - designates size and is the energy level number

l

angular momentum quantum number - describes the shape (subshell) of how electronic motion looks in space. Is either 0, 1, 2, 3 (spdf)

m_l

magnetic quantum number - specifies orientation (-2, -1, 0, 1, 2)

m_s

spin quantum number - specifies spin direction (+1/2 or -1/2)

Electron shell

the set of orbitals within the same n are called an electron shell eg 3s, 3d, and 3p are all in the 3 shell (is electron shell same as energy level?)

effective nuclear charge (Zeff)

the magnitude of a positive charge that is experienced by an electron in an atom (ie how much the valence electrons feel the protons). The farther away a valence shell is from the nucleus the less effective Zeff. Row matters more than column because you +/- a whole shell

shielding

when core electrons block or shield some of the positive charge of the protons from the outer electrons

atomic radius

the distance between the nucleus of an atom and its valence shell (row matters more than column)

ionic radius

the radius of a cation/anion. A cations radius decreases (compared to neutral atom) due to a reduction of electron electron compulsion. There is a significant decrease in radius when ALL of an atoms valence electrons are removes

ionization energy

the minimum energy required to remove an electron from an atom in the gas phase (this is an endothermic reaction). 1st IE always takes the least energy. Once valence shell is removed it is extremely difficult to remove another

What does removal of an electron create?

an ion

electron affinity

the energy released when an atom in the gas phase accepts an electron (+ values indicate released energy, it is an exothermic process). How willing is it to accept an electron?

electronegativity

the tendency or measure of how well an atom or bond will attract electrons