Chapter 1.2: Lewis Model of Bonding
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What is an atom or group of atoms bearing a positive charge?
cation
Define nonbonding electrons
valence electrons not involved in forming a covalent bond; unshared pairs or lone pairs
What group of elements have exceptions to the octet rule?
Group 3A elements
What is energy added or released when an electron is added to an atom or molecule?
electron affinity
What is a measure of the force of an atom’s attraction for electrons?
electronegativity
Define bond length
the distance between atoms in a covalent bond in picometers
Define electron affinity
energy added or released when an electron is added to an atom or molecule
Why does electronegativity decrease down a group?
• Decreases down a group because the increasing distance of the valence electrons from the nucleus results in a lower attraction between the nucleus and these electrons
What is the distance between atoms in a covalent bond in picometers?
bond length
Why does electronegativity increase within a period?
• Increase within a period because of the increasing positive charge on the nucleus results in a greater force of attraction for the atom’s valence electrons
Define electronegativity
a measure of the force of an atom’s attraction for electrons
What is group 1A-7A elements react to achieve an outer shell of eight valence electrons?
octet rule
What is attraction between oppositely charged ions?
ionic interaction
How are ions formed?
• Ions are formed by the transfer of electrons from the valence shell of an atom of lower negativity to the valence shell of an atom of higher electronegativity • Ions form when difference in electronegativity is 1.9 or greater
What are Dative bonds?
o Construction of a Lewis structure from neutral groups or atoms to achieve an octet gives rise to bonds where the two electrons come from only a single groups or atom while the other group or atom involved in that bond does not contribute any electrons. Such bonds are referred to as dative or coordinate covalent
Define formal charge
the charge of an atom in a polyatomic ion or molecule
What are valence electrons not involved in forming a covalent bond; unshared pairs or lone pairs?
nonbonding electrons
Define cation
an atom or group of atoms bearing a positive charge
Define bond dipole moment
a measure of the polarity of a covalent bond; the product of the charge on either atom of a polar bond times the distance between the atoms
What is a chemical bond formed between two atoms by sharing one or more pairs of electrons?
covalent bond
What is a covalent bond between atoms whose difference in electronegativity is between 0.5 and 1.9?
polar covalent bond
Define bonding electrons
valence electrons involved in forming a covalent bond (shared electrons)
What is the formula for formal charge?
o Formal Charge = number of valence electrons in the neutral, unbonded atom – (all unshared electrons + one half of all shared electrons)
What is an atom or group of atoms bearing a negative charge?
anion