W3 From atoms to molecules ll

Question 1

What is an atomic orbital?

Answer 1

Atomic orbitals can hold two electrons (of opp spins) and is described as a 3D region within which there is a 95% probability of finding the electrons.

Question 2

What is the principal quantum number?

Answer 2

Principle quantum number n. n=1 the lowest-energy shell closest to the nucleus.

Question 3

How many subshells are there?

Answer 3

4 subshells (s,p,d,f)

Question 4

How many orbitals in an S, P, D and F sub shell

Answer 4

S=1 orbital
P= 3 orbitals
d= 5 orbitals
F= 7 orbitals

Question 5

An orbital can hold how many electrons?

Answer 5

2

Question 6

A shell can hold up to how many electrons?

Answer 6

Each shell can contain up to 2n^2 electrons, where n is the number of the shell.

Question 7

What are valence electrons and what does valence mean?

Answer 7

Outermost electrons
Valence= electrons an atom must lose or gain to attain the nearest noblest noble gas.
E.g. C has 4 valence electrons (config:1s2 2s2 2p2) it needs 4 e- to become …. 2p6, so valence is 4

Question 8

What is the Aufbau Principle?

Answer 8

Orbitals and shells fill in order of increasing energy. 1s shell lower in energy than a 2s shell, which is lower in energy than a 3s shell.

Atomic orbitals in the same shell = s atomic orbital is lower in energy than p and p is lower in energy than d.

Question 9

What is the Pauli exclusion principle?

Answer 9

each atomic orbitals can hold a maximum of 2 electrons having opposite spin

Question 10

What is Hund’s rule?

Answer 10

When there are two or more orbitals of the same energy (degenerative orbitals), electrons go into different orbitals rather than pair up in the same orbital.

Question 11

What is the Octet rule?

Answer 11

A filled shell of electrons is especially stable

Atoms transfer or share electrons to attain a filled shell of electrons (noble gases)
8 valence electrons for the elements in the second row (Octet Rule)

Elements in the third and higher rows can have an “expanded octet” e.g. Al, Si, P, S, Cl

Question 12

What does each sub shell contain?

Answer 12

One or more atomic orbital. Exact orientation of an
orbital in the space (px, py or pz). Identified by the magnetic quantum number ml

Question 13

How many electrons in:
shell 3?
shell 4?

Answer 13

=18 (3S 3P 3P 3P FIVE 3D)
=32 (4S 4P 4P FIVE 4D SEVEN 4F)

Question 14

Ground-state electronic configuration: How can we determine it? (3)

Answer 14

1. Aufbau principle
2. Pauli exclusion principle
3. Hund’s rule

Question 15

What occurs in a nonpolar covalent bond?

Answer 15

Electrons are shared equally

Question 16

What is a Polar covalent bond?

Answer 16

Unequally shared pair of bonding electrons

Question 17

What is the definition of Electronegativity?
Which atom attracts the shared electrons in a diatomic molecule?

Answer 17

Power of an atom in a molecule to attract electrons to itself.
The more electronegative atom.

Question 18

Pauling electronegativity values:
When are Ionic bonds formed?
When are covalent bonds formed?

Answer 18

Ionic bonds form when electronegativity
difference between 2 atoms is > 1.7

Covalent bonds form when electronegativity
difference between 2 atoms is < 1.7

Question 19

What is meant by intermolecular forces?

Answer 19

Attraction forces between molecules (non-bonding interactions)

Question 20

3 types of intermolecular forces:

Answer 20

1) Dipole-dipole interactions
2) Van der Waals Forces
3) Hydrogen bonding

Question 21

Dipole-dipole interactions

Answer 21

Interactions between the positive end of one
dipole and the negative end of another dipole

Question 22

Van der Waals Forces:

Answer 22

Relatively weak forces of attraction that exist
between nonpolar molecules. Distance-dependent interactions. Called induced dipole–induced dipole interactions

Question 23

Hydrogen bonding

Answer 23

• Attractive force between the H attached to an
  electronegative atom of one molecule and an electronegative atom of the same
  (intramolecular) or a different molecule (intermolecular). i.e. H2O
• NOF Elements

Question 24

What is the lewis structure?

Answer 24

Each valence electron is symbolised by a dot
A bonding pair of electrons is symbolised by a pair of dots or by a dash ( -)
Sharing of one pair of electrons - single bond
Sharing of two/three pairs of electrons - double/ triple bond

Question 25

What typical elements have lone pairs?

Answer 25

Oxygen atoms, nitrogen atoms, and the halogens
(F, Cl, Br, I)

Question 26

What is sp3 hybridisation?
What is the shape?
Bond angle?

Answer 26

-Used when C forms 4 single bonds, all blended
-4 sp3 orbitals of equal E
-Tetrahedral
-Bond angles 109.5°

Question 27

What is sp2 hybridisation?
What is the shape?
Bond angle?

Answer 27

-Used when C forms a double bond, 2s plus 2 2p blended, 3 sp2
-Orbitals of equal E + 1p orbital
-Trigonal geometry
-Bond angles 120°

Question 28

What is sp hybridisation?
What is the shape?
Bond angle?

Answer 28

-Used when C forms a triple bond or a cumulate Double bond, 2s plus 1 2p blended, 2 sp orbitals of equal E + 2p orbital
-Linear geometry
-Bond Angles 180 °