AP Chemistry

Valence and Core Electrons

Electrons in the atom’s outermost orbitals (usually those in the highest energy level) are called valence electrons.

Valence electrons participate in bonding.

Core electrons are all the other electrons that are not valence.

Attraction and Repulsion in an Atom

Coulombic Attraction - the attraction between oppositely charged particles.

Protons & electrons are attracted to one another

Simultaneously, electrons in the electron cloud are repelling one another.

Sheilding Effect

Shielding Effect - as the number of energy levels increases, the distance between the nucleus and outermost electrons increases, and the attraction between the nucleus & the outermost electrons decreases. Inner electrons partially block (shield) the positive charge, causing valence electrons to experience a lower effective nuclear charge, making them easier to remove and increasing atomic radius.

Effective Nuclear Charge (Z)

Across a period (row), the number of energy levels in constant, but the number of protons the nucleus increases.  Increasing the number of protons across a period increases attraction between the nucleus & the outermost electrons.

Columbic Atraction Periodic Trend

Increases across periods - more protons

Decreases down columns - more energy levels

Atomic Radius Periodic Trend

Decreasees across rows - more protons, higher columbic attraction

Decreases down columns - more energy levels, lower columbic attraction

Isotopes

Atoms of the same element that differ by the number of neutrons in the nucleus leading to different masses of isotopes

Average Atomic Mass + Calculation

The weighted average mass of an element’s isotopes

Average Atomic Mass = ∑(percent abundance x mass number)

Mass Spectrometry

I don’t fucking know (1.1)

Properties of Metals

• Usually solid at room temp

• Malleable & ductile (can be shaped without breaking)

• Conductive

• Lose electrons to form cations

Properties of Metlaloids

• Have properties that are in between those of metals & nonmetals

• Commonly used in electronics

Properties of Nonmetals

• Usually gases at room temp

• Brittle if solid

• Not conductive

• Gain electrons to form anions

Seperating Metals, Metaloids, and Nonmetals on the Period Table

.

Heisenberg Uncertainty Principle

it is impossible to know precisely both the velocity and position of an electron at the same time.

Quantum Numbers

assigned to describe the probable location of each electron in an atom.

• n = principal quantum number (energy level)

• l = angular momentum quantum number (orbital shape/sublevel) - idnidentifies sublevel an electron resides in, (s=0, p=1, d=2, f=3)

• m_l = magnetic quantum number (orbital orientation)

• m_s = magnetic spin quantum number (relative spin direction)

Electron Configurations

.