Molecular shape (Lewis, VSEPR, Mol. Orbital)

• Electron: is a negatively charged subatomic particle

  • Electron shell: orbit/rings around a nucleus, represented by n = a number

    • Subshell: space where electrons are, giving info about where they are and what they are doing. There is an s, p, d, and f orbital

      • s holds 2 electrons (holds 1 atomic orbital)

      • p holds 6 electrons (holds 3 atomic orbitals)

      • d holds 8 electrons (holds 4 atomic orbitals)

      • f holds 14 electrons (holds 7 atomic orbitals)

      • atomic orbitals hold 2 electrons

        

• Covalent bond: is when two atoms share an electron in order to fill its octect

• Ionic bond: is when one atom transfer electrons to another, creating cation and anion

  • Cation: when an atom loses an electron, it forms a positive cation (pawsitive!)

  • Anion: when an atom gains an electron, it forms a negative anion

    • Cations and anions are attracted to each other (opposite charges)

• Lewis Structure/Lewis Dot Structure: is a simplified drawing of how the valence electrons of an element bond with the other valence electrons of another element, and if there are any lone pairs

  • Central atom: is typically the atom in the middle, forming the most bonds

• Electrons are negatively charged, and negatives repel. So, when forming molecules, the electrons make a shape to maximize the distance between themselves and other electrons.

  • Electron domains/Steric number: region where electrons are most likely to be found, bonding and non bonding. Note: a bond, double bond, triple bond, or lone pair, all count as only 1 electron domain

• VSEPR (Valence Shell Electron Repulsion) Theory: model to predict 3D shape of a molecule based on number of electron bonds around the central atom

  • AXE notation: a way to count electron domains and predict what the shape of the molecule will be. A is the central atom, with a subscript of 1. X is the amount of bonds the central atom is forming to other atoms. E is the amount of lone pairs of electrons on the central element. The steric number is the sum of X and E.

    • Different shapes form based on steric number and the amount of lone pairs

    • Typically molecules will have 2-6 electron domains, flashcards here: https://knowt.com/flashcards/5797fac8-0f6e-493f-91eb-3ef80e2a443b

      • 2 electron domains: linear

      • 3 domain electron domains: trigonal planar (AX3), bent (AX2E1)

      • 4 electron domains: tetrahedral (AX4), trigonal pyramidal (AX3E), bent (AX2E2)

      • 5 electron domains: trigonal bipyramidal (AX5), seesaw (AX4E), T-shaped (AX3E2), linear (AX2E4)

      • 6 electron domains: octahedral (AX6), square pyramidal (AX5E), square planar (AX4E2)

• Molecular Orbital Theory (MOT): a way to explain atoms bonding together and a molecules’ shape using quantum mechanics (no, we’re not talking about that).

  • In MOT, electrons are described as “delocalized” through out the entire molecule, in electron clouds (space where electrons could be). (Compared to VSEPR and Lewis)

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    • Sigma bond: generally, one bond, where the electron clouds overlap. it takes less energy to be here, so these fill up first. These are usually stronger than pi bonds.

      • Sigma*/Sigma star: bonding two elements means you have another orbital you need to maintain, so that is the anti-bonding orbital.

    • Pi bond: when there is more overlap of electron clouds (p orbitals), pi bonds form (psst… pi is two letters, and has two slots)

      • Pi*/Pi star:

    • Bond Order: (bonding e - antibonding e)/2

  • Paramagnetic

  • Diamagnetic

  • HOMO: Highest Occupied Molecular Orbital (higher energy than LUMO)

  • LUMO: Lowest Unoccupied Molecular Orbital (lower than HOMO)

• Valence Bond Theory (VBD):

• Lewis Dot Structure Weakness:

  • Depicts molecules as 2D

• MOT Weakness:

  • Predicting Shape

• VBD Weakness:

  • Predicting magnetic properties

Hybridization

• Hybridization: low energy state is preferably for elements, so you can hybridize atomic orbitals (s,p,d,f) into hybrid orbitals (like sp) which is a new shape!

  • To find hybridization: consider number of electron domains, if it is 2 then the hybridization is sp, if it is 3 then the hybridization is sp2, if it is 4 then it is sp3, if it 5 then it is sp3d, if it is 6 then it is sp3d2

    • Ex: a hybridized is a new shape, so CH4 has 4 sp3

Polarity

• Electronegativity: measure of how strong an element is pulling electrons towards itself. Smaller elements tend to be more electronegative.

• Polarity: when differences of electronegativities happen, there is an uneven distribution of electron density. in essence, the electrons aren’t being evenly shared

  • Polar covalent: when 2 elements bond and share an electron, but one pulls harder because of the higher electronegativity

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  • Dipole moment: measures separation of positive and negative charge within a molecule

  • Polar bonds

  • Polar molecules

• Non-polar covalent: when two atoms share atoms equally, so there is no dipole moment. this occurs between bonds of the same element, or when the electronegative difference is small (>0.4

Metallic/Ionic/Covalent Bonds

• Covalent Bonds: are typically between a non metal and a non metal

• Ionic Bonds: are typically between and non metal and a metal

• Metallic Bonds: are usually between a metal and a non metal

Oxidation, Nomenclature,

Gas Laws

shit is still underconstruction, look at these screenshots