L2- atoms compounds and chemical bonding

Question 1

what does the big number of an atom on periodic table represent

Answer 1

mass no (protons + neutrons)

Question 2

what does the small number of an atom on periodic table represent

Answer 2

atomic no. (of protons and electrons)

Question 3

how do electrons fill orbitals

Answer 3

1. with increasing energy S - D
2. with opposing spin
3. 1 in each orbital before pairing

Question 4

what are orbitals

Answer 4

the spaces around an atom that will contain electrons

Question 5

what is the quantum state of an electron in an orbital determined by?

Answer 5

1. principle quantum number ( n= 1 / 2 /3)
2. orbital quantum number ( L= 0 / 1 / 2)
3. magnetic quantum number (M=)
4. spin quantum number ( S= +1/2 or -1/2)

Question 6

what is principle quantum number?

Answer 6

average distance of electron from nucleus

shell 1/2/3

Question 7

what is orbital quantum number?

Answer 7

corresponds to shape of orbital 
(S) L=0
(P) L=1 
(D) L=2
(F) L=3

Question 8

what is the orbital quantum number of S orbital

Answer 8

0

Question 9

what is magnetic quantum number

Answer 9

orientation of orbital
eg for P orbitals
-1 , 0 , 1

eg for D orbitals
-2 , -1 , 0 , +1 , +2

Question 10

what is spin quantum number

Answer 10

direction of electron spin

S = +1/2 or -1/2

Question 11

what letter corresponds to shell 
1
2
3
4

Answer 11

k
l
m
n

Question 12

what is relative energy of orbital?

Answer 12

principle quantum number (n) + orbital quantum number (L)

Question 13

what is valency of an atom

Answer 13

number of bonds that a certain atom can make (eg 4 for C ) + formal charge

Question 14

what is the general rule for covalent / ionic bonding relating to electronegativity

Answer 14

if change in X > 1.7 —- ionic bond

if change in X < 0.7 —- covalent bond

Question 15

what happens to orbitals in covalent bonding

Answer 15

they merge and resulting orbitals have different energy levels

Question 16

define bonding orbital

Answer 16

the orbital that has lower energy than original atomic orbitals

Question 17

define antibonding orbital

Answer 17

the orbital that has higher energy than original atomic orbitals

Question 18

define non bonding orbitals

Answer 18

orbital doesn’t increase / decrease energy - no covalent bonds form

Question 19

what bonds can non bonding orbitals form

Answer 19

dative covalent

Question 20

where is the electron density for pi bond

Answer 20

above / below plane of molecule

Question 21

define conjugated bond

Answer 21

alternating single and double (or triple) bonds resulting in delocalisation of electrons in p orbitals
(eg benzene)

Question 22

define resonance

Answer 22

when a compound can be represented as more than one structure because it alternates between them.

Question 23

define resonance hybrid

Answer 23

when a molecule exhibits resonance it is displayed as a hybrid of its forms

Question 24

effects of conjugated bonds on molecule

Answer 24

increases stability

lowers overall energy

Question 25

define aromaticity

Answer 25

property of cyclic (conj ring) structures with pi bonds in resonance gives increased stability than what would be expected from conjugation alone

Question 26

what is huckels rule?

Answer 26

determining aromaticity | any planar ring molecule with 4n + 2 pi electrons is aromatic