Chapter 8: Basic Concepts of Chemical Bonding Flashcards
What are the 3 types of chemical bonds?
ionic | covalent | metallic
What are ionic bonds?
electrostatic attractions between oppositely charged ions
What are covalent bonds?
atoms sharing electrons
What are metallic bonds?
electrons are free to move from one atom to another
What is the octet rule?
atoms tend to gain/lose/share electrons until they are surrounded by 8 electrons (want to be like noble gas)
What does the electron configuration of a noble gas consist of?
FULL s and p orbitals
What is the usual pairing of an ionic bond?
a metal from 1A/2A and a nonmetal
What does an atom’s ionization energy indicate/affect electron transfer?
indicates how easily an atom can give up an electron
What does an atom’s electron affinity effect electron transfer?
measures how much an atom wants to gain an electron
What is electron transfer?
when one atom readily gives up an electron (low IE) and the other electron readily accepts an electron (high EA)
What are the 3 characteristics of ionic substances?
brittle | high melting point | crystalline
What type of process (endothermic or exothermic) is loss of electrons from an atom?
endothermic
What type of process (endothermic or exothermic) is gaining of electrons of an atom?
exothermic
Why are ionic compounds stable?
attraction between oppositely charged ions draws them closer together = releasing energy (exothermic) = forms a lattice
What is lattice energy?
energy needed to completely separate 1mol of a solid ionic compaound into its gaseous ions
What describes the stability of a lattice structure?
lattice energy
What type of process (endo/exo) is forming ionic compounds?
exothermic
What are the 3 things that the lattice energy magnitude of a solid depend on?
charges of the ions (mainly) | ionic size and their arrangement in the solid
What is the relationship between lattice energy and the size and radii of the ions?
lattice energy increases as ionic size increases and ionic radii Decreases and distance between ions increase
What is the limitation/restriction to adding/removing electrons from s and p elements
s-block: can only remove e- from valence shell | p-block: can only add e- to valence shell = otherwise its energetically unfavorable
How are electrons added or removed to/from transition metals?
e- from valence shell are lost first | subsequent removal comes from d-orbital electrons
How could atoms have noble-gas electron configurations?
by sharing “borrowing” electrons
What is a covalent bond?
chemical bond formed by sharing a pair of electrons
How do covalent bonds stick if it is the sharing of electrons?
the shared electrons (any 2 electrons) are in between the atoms’ nuclei, the attractive forces between electron-nucleus “hold” the bond together
What are non-bonding pairs in the Lewis Dot Structure?
lone pairs
What is bond polarity?
measure of how equally/unequally the electrons in any covalent bond are shared
What is a non-polar covalent bond?
electrons are shared equally
What is a polar covalent bond?
one of the atoms exerts a greater attraction for the bonding-electrons than the other atom
What separates a polar covalent bond from an ionic bond?
difference in magnitude of attraction between an atom for the bonding electrons compared to another atom
What is electronegativity?
ability of an atom in a molecule to attract electrons to itself
What determines the type of chemical bond in a molecule?
the electronegativity of an atom
What 2 things affect an atom’s electronegativity?
ionization energy and electron affinity
What must the EA and IE of an atom be in order to have an increase in electronegativity?
EA must be (-) and IE increases = resists having its e- taken away
Who is Linus Pauling?
developed the first and most widely used electronegativity scale based on thermochemical data
What is the periodic TREND for electronegativity?
increases left –> right | increase UPward a group
What is the electronegativity in atoms with a non-polar bond?
similar electronegativities
What is the electronegativity in atoms with a polar-bond?
one of the atoms is MORE electronegative than the other and the electron density cloud shifts more toward the more electronegative atom
What is the electronegativity in atoms with a ionic bond?
difference in electronegativity MUST BE > 2
What are polar molecules attracted to and why?
ions, due to their partial charges
What is a dipole?
whenever 2 opposite electrical charges are separated by a distance
What is a dipole moment (µ)?
quantitative measure of the magnitude of a dipole
What are the 3 characteristics of molecular compounds?
low melting point | low boiling point | non-electrolyte behavior in water
What is expected when covalent bonding is dominant?
compounds exists as molecules
How can we distinguish between an ionic and covalent bond?
use the differences in electronegativity
What is a formal charge?
potential charge the atom would have if each bonding e- pain in the molecule were shared equally between 2 atoms
What are the 2 ways to identify the dominant Lewis structure?
formal charges are closest to 0 | (-) charges reside on the most electronegative atoms
What are resonance structures?
placement of atoms are the same but vary in placement of electrons
What bonds do resonance structures only occur with?
double bonds
What are the 3 exceptions to the octet rule with molecules and polyatomic ions?
odd # electrons | atom has fewer than 8 valence e- | atom is hypervalent
What is hypervalent?
atom has more than 8 valence electrons
What are hypervalent molecules formed only for?
central atoms on Period 3 and below due to their large size
What is the stability of a molecule related to?
the strength of its covalent bond
What happens as the number of bonds between 2 atoms increase to the bond distance, bond enthalpy and bond strength?
shorter distance = atoms closer together = increase in bond enthalpy = increase bond strength
