KEMORG Review 1 - Introduction and Recap

(1.2) 2 atoms bond in order to _____

• achieve octet e- config.

• achieve stability

• increase electronegativity

• become more acidic or basic

(1.2) Bonding that involves sharing of electrons between elements with little to no electronegativity difference

• ionic

• metallic

• covalent

• nuclear

Answer explanation

ionic bonding is between metal and non metal (high electronegativity difference).

both bonds are bound by electrostatic attraction (ions in ionic, electron cloud a nuclei in covalent)

(1.2) which of the following is a MOLECULE

• Mg

• NaCl

• e-

• H2

Answer explanation

Mg = atom

NaCl = ionic compound

e- = subatomic particle

H2 = molecule

(1.2) How many covalent bonds can be formed from an atom with 5 valence electrons

• 2

• 3

• 4

• 5

Answer explanation

remaining electrons stay as lone pair/ non bonded pair.

lone pairs:

• - more repulsion than bonding pairs

• - more lone pairs = smaller angles between atoms in compound compared to without

(1.3) Lewis structures represent the actual bonding between atoms in a compound

• true

• false

Answer explanation

simplified representation of e- distribution in a compound.

• - dot = electron

• - line = 1 covalent bond (1 pair of e-)

TO DRAW:

• - central atom is least electronegative

• - (octet v.e. - actual no. v.e. [add e- if anion subtract e- if cation])/2 = no. of bonds

• - draw skeletal structure, complete octet from central with double/ triple bonds / lone pairs then peripheral atoms

• - calculate FC to gauge stability, sum of FC = charge of ion

(1.3) Which formal charge is most stable?

• -3

• +2

• 1

• 0

Answer explanation

FC closer to 0 = more stable

formula = v.e. - (sum of dots and lines in lewis)

(1.4) Ethanol (CH3CH2OH) and dimethyl ether (CH3OCH3) are ______

• isotopes

• isomers

• acids

• alkanes

Answer explanation

Same molecular formula, different arrangement of atoms

constitutional = differ in the order with which atoms are connected

stereoisomers = differ in spatial arrangement but same order of connectivity between atoms

(1.5) Elements in 3rd row of periodic table tend to be octet exceptions, specifically

• incomplete octet

• expanded octet

• free radicals (odd no. of e-)

• even no. of e-

(1.6) what differs in between resonance structures

• placement of atoms

• sum of formal charges

• arrangement of electrons

• location of sigma electrons

Answer explanation

depicts simplification of fractional bonds with multiple structures that differ in location of double or triple bonds that collectively describe the true bonding of an atom

(1.6) what actually occurs in a resonance hybrid

• electrons split into halves or thirds for each fractional bond

• electrons are expelled for more stability

• electrons are delocalized over 2 or more atoms

• double / triple bond changes location every millisecond

Answer explanation

principles of resonance:

• - structures as depicted aren't real, hybrid of all of them is real and with max stability

• - structures aren't in equilibrium (e- don't move from one to another)

• - resonance structures aren't isomers: isomers have different electron AND atom arrangement