Chapter 10

Bonding pairs

pairs of electrons found in the space between the atoms

Lone pairs

pairs of electrons localized on an atom

% Ionic Character Formula

% ionic character= experimental dipole moment/calculated dipole moment

Lewis structure

A Lewis structure is a structural representation of a molecule where dots are used to show electron positions around the atoms and lines or dot pairs represent covalent bonds between atoms. A Lewis electron dot diagram (or electron dot diagram or a Lewis diagram or a Lewis structure) is a representation of the valence electrons of an atom that uses dots around the symbol of the element. The number of dots equals the number of valence electrons in the atom. ... The total number of electrons does not change. *Valence electrons are equal to the group number of the element* Lewis structures (also known as Lewis dot structures or electron dot structures) are diagrams that represent the valence electrons of atoms within a molecule. These Lewis symbols and Lewis structures help visualize the valence electrons of atoms and molecules, whether they exist as lone pairs or within bonds.

Covalent bond

A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding.

Non-polar covalent bond

A non-polar covalent bond is a type of chemical bond that is formed when electrons are shared equally between two atoms. ... It further means that there is no separation of charges between the two atoms or both the atoms have similar electronegativity. *Electronegativity 0-0.39*

nonbonding electron

A nonbonding electron is an electron in an atom that does not participate in bonding with other atoms. Double bonds a chemical bond in which two pairs of electrons are shared between two atoms. Triple bond : a chemical bond in which three pairs of electrons are shared by two atoms in a molecule — compare double bond, single bond.

Polar covalent bond

A polar bond is a covalent bond between two atoms where the electrons forming the bond are unequally distributed. This causes the molecule to have a slight electrical dipole moment where one end is slightly positive and the other is slightly negative *Electronegativity 0.4-2.0*

Dipole-Dipole Moment

Dipole moments occur when there is a separation of charge. They can occur between two ions in an ionic bond or between atoms in a covalent bond; dipole moments arise from differences in electronegativity. The larger the difference in electronegativity, the larger the dipole moment.

Ionization energy

Energy associated with loss of one electron from neutral gaseous atom

Electron Affinity

Energy change when an electron added to a neutral atom

Covalent forces

Forces: Electrons (-) and nuclei (+) attract one another Electrons (-) repel each other Nuclei (+) repel each other Attractive force stabilize and lower energy Repulsive forces destabilize and raise energy

Types of chemical bonds

Ionic, Covalent, Hydrogen, Metallic *Chemical bonding, any of the interactions that account for the association of atoms into molecules, ions, crystals, and other stable species that make up the familiar substances of the everyday world.*

Ionic bonds

Metal and nonmetal form binary ionic compound Valence orbitals of metal emptied Nonmetal achieves e- config. of next noble gas atom NaCl: Na+ loses e- to Cl-, Cl- achieves [Ar] e- configuration

Metalic bond

Metallic bond, force that holds atoms together in a metallic substance. ... The atoms that the electrons leave behind become positive ions, and the interaction between such ions and valence electrons gives rise to the cohesive or binding force that holds the metallic crystal together. *Electronegativity >2.0

Orbital Overlap as Two H Atoms Approach

Overlap of 1s atomic orbitals increases Wave amplitudes add, generating new molecular orbital with high electron density Bonding orbitals constructed by combining atomic orbitals from adjacent atoms

Duet rule

The duet rule states that hydrogen and helium may have no more than two electrons in their valence shells. The rule comes from quantum mechanics, which says that the lowest energy level (n = 1) of an atom can contain only two electrons.

Formal charge

The number of valence electrons in an isolated atom minus the number of electrons assigned to the atom in the Lewis structure assigned net charge to each atom in a molecule or ion Does not necessarily represent actual charges on the atoms Used to evaluate nonequivalent Lewis structures Atoms in molecules try to achieve formal charge of zero Any negative formal charges on most electronegative atoms Assume: Lone pair electrons belong entirely to the atom in question Shared electrons divided equally between the two atoms

Octet rule

The octet rule refers to the tendency of atoms to prefer to have eight electrons in the valence shell. When atoms have fewer than eight electrons, they tend to react and form more stable compounds As the saying goes, all rules are made to be broken. When it comes to the octet rule, that is true. Exceptions to the octet rule fall into one of three categories: (1) an incomplete octet , (2) odd-electron molecules , and (3) an expanded octet.

Molecule

atoms bound together by sharing pairs of electrons using the atomic orbitals of the bound atoms

Which compound is most likely to consist of a Ionic bond? a. CH4 b. N2O c. MgF2

c. MgF2

formula for ionic compounds

formulas to names 1. write the name of the metal and if its a transition metal the roman numeral 2. the nonmetal second with "-ide" at the end (BeI2=Beryllium Iodide) names to formulas 1.write formula of the metal 2. write nonmetal formula 3. the total charge must equal 0 (Copper (II) iodide= CuI2) Ex: what compound will form from calcium & bromine? Ca: [Ar] 4s2 - lose 2 e- to form Ca2+ Br: [Ar] 4s2 3d10 4p5 - gain 1 e- to form Br- Ca2+ + Br-→ CaBr2

Electron orbital

how electrons are spatially distributed surrounding the nucleus; the area where an electron is most likely to be found *In chemistry and quantum mechanics, an orbital is a mathematical function that describes the wave-like behavior of an electron, electron pair, or (less commonly) nucleons. An orbital can contain two electrons with paired spins and is often associated with a specific region of an atom.*

Resonance

more than one valid Lewis structure can be written for a particular molecule Actual structure is an average of the resonance structures Electrons are really delocalized - they can move around the entire molecule Instead of 2 single bonds and 1 double bond, 3 partial double bonds since all bonds are the same length

Period number

number of electron shells

Group number

number of valence electrons

Born-Harber cycle

relates lattice energies of ionic compounds to ionization energies, electron affinities, and other atomic and molecular properties

Electronegativty

the ability of an atom to attract electrons when the atom is in a compound *Electronegativity increases from left to right and from bottom to top*

Bond legnth

the average distance between the nuclei of two bonded atoms Bond length (of covalent bond) is nuclear separation distance where molecule is most stable Trend: bonds become longer as the radii of the atoms become larger

Lattice energy

the energy released when one mole of an ionic crystalline compound is formed from gaseous ions

Bond energy

the energy required to break a chemical bond and form neutral isolated atoms 1. Bond strength increases as more electrons shared between atoms 2.Bond strength increases as electronegativity difference (ΔΧ) between bonded atoms increases 3. Bond strength decreases as bonds become longer