exam 2 Flashcards
chemical bonds
forces that hold atoms together
octet rule
atoms tend to bond to fill their valence orbital
- atoms seek to attain a “noble gas electron configuration”
2 types of covalent bonds
polar covalent: sharing of electrons is not as equal
non polar covalent: equal sharing of electrons
“which one has more ionic character?” means
which one has the greater electronegativity difference (more ionic)
ionic bonds
electron transfer where you have a lot of electronegativity
THEY SELFISH
ionic compounds are comprised of ___________
oppositely charged ions. they form when metals react with nonmetals.
*transfer of electrons from metal to nonmetal
6 properties of ionic compounds
- Contain a metal and nonmetal (large electronegativity difference)
- Bond strength (very strong bonds minus cellular conditions)
- **High melting and boiling points
** (b/c lots of negative & positive interactions – very stable & don’t want to be broken apart) - Crystalline structure
- Solubility in water (very soluble in water – why they’re weak in cellular conditions b/c cells are full of water)
- Conductivity (very low conductivity in solid state, however very soluble in H2O so high conductivity in aqueous solution)
bond length
distance b/w 2 atoms where the energy is lowest
covalent bonds form when ___________
electrons are shared between bonds
nonpolar covalent bonds vs. polar covalent bonds
nonpolar covalent: equal sharing between atoms in a molecule
polar covalent: unequal sharing between atoms in a molecule
5 properties of molecular (covalent) compounds
- Largely form when nonmetals react with other nonmetals
- Weak bond strength (weak bonds – broken much easier than ionic bonds)
- Often have low melting and boiling points
- Low solubility in water
- Low conductivity (b/c no ions are floating around)
How are binary ionic compounds named? (one metal and one nonmetal)
binary ionic compounds: contain a cation and anion
- name of the cation (metal) is named first and unchanged
- name of the anion (nonmetal) contains the suffix -ide
examples:
CsF (cesium fluoride)
MgO (magnesium oxide)
Ca3P2 (calcium phosphide)
Al4C3 (aluminum carbide)
Na2O (sodium oxide)
aming binary compounds (transition metals) + exceptions
- for atoms that can form different types of ions
- use ROMAN NUMERALS for charge
exceptions: Zn2+ , Ag+, Cd2+ (don’t need to use roman numerals for these elements)
how to name compounds using polyatomic ions
- special names that need to be memorized
use parentheses when you have more than 1 polyatomic
naming ionic hydrates
- naming is the same as ionic but has the extra aspect of hydrate in it
- naming hydrates: use Greek prefixes and the word “hydrate”
how to name binary covalent compounds
binary covalent compounds: contain two nonmetals
- first element is named
- second element contains suffix -“ide”
- prefixes used to denote number of atoms present for elements
mono never used for first element but used for the second element
ex. NO2 - nitrogen dioxide, IBr7- iodine heptabromide
what are acids
substances that release H+ when dissolved in water
how to name acids
- if anion ends in -ide, add prefix hydro- and suffix -ic
ex. HCL - hydrochloric acid - if anion ends in -ate, don’t use hydro- and add suffix -ic
ex. H2SO4 - sulfuric acid - if anion ends in -ite, -ite is replaced with -ous
ex. HNO2 - nitrous acid
this only applies for when they are in water, because in gaseous states, they are named differently
how are Lewis structures drawn for molecules
using only valence electrons, create dots and bonds on the name of the element
difference in Lewis structures for ionic compounds and molecules (covalent)
They are only helpful for covalent molecules, they don’t do much to show anything for ionic molecules
Octet and Duet Rule
octet rule: main group element want to obtain 8 valence electrons
g*duet rule**: hydrogen atoms may have no more than 2 electrons in their valence shells
exception of octet rule: molecules with odd numbers of electrons
atoms in molecules with an odd number of electrons cannot form stable octets
- atom might not enough to form 8 (fine)
- more electronegative atom will have more electrons
exception 2 to octet rule: electron-deficient molecules
molecules with not enough electrons will have central atoms with fewer than 8 electrons
exception 3 to octet rule: hypervalent molecules know this
- extra electrons can be placed on the central atom
- only for elements in period 3 and beyond
- often happens for sulfur and phosphorus
formal charge and formula
formal charge: charge assigned to an atom in a molecule (hypothetically: made up #’s)
FC = V - N - B )
V - valence electrons
N - non bonding electrons (one pairs)
B - # of bonds