L2: Atoms, compounds & chemical bonding

Question 1

Structure of an atom

Answer 1

Small, postively charged nucleus surrounded by electrons

Question 2

What is the nucleus composed of?

Answer 2

Neutrons & protons

Question 3

What is the atomic number?

Answer 3

Number of protons

Question 4

What is each electron in an atom described by?

Answer 4

4 quantum numbers

Question 5

What are the 4 quantum numbers?

Answer 5

1) Principle quantum number n
2) Azimuthal quantum number (L)
3) Magnetic quantum number (ml)
4) Spin magnetic quantum number (ms)

Question 6

Describe principal quantum number n

Answer 6

Which shell an atom belongs to, distance between electron & nucleus

Question 7

Describe azimuthal quantum number l

Answer 7

Type of orbital an atom is in
- Electrons with same azimuthal quantum no. are in a subshell

l can range from 0 to n-1

Question 8

Describe magnetic quantum number ml

Answer 8

Number of orbitals and their orientation within a subshell

ml ranges from -l to -l, there are 2l+1 orbitals per subshell

Question 9

Describe spin magnetic quantum number ms

Answer 9

Orientation of the spin angular momentum of each electron

-1/2 or +1/2

Question 10

3 different orbitals

Answer 10

s,p,d

Question 11

What are orbital lobes?

Answer 11

Area where we find a high probability density for locating electrons

Question 12

What do the different colours on orbital lobes indicate?

Answer 12

2 differnt phases of wavefunction

Question 13

Probability of nodal planes of locating an electron

Answer 13

0

Question 14

How does electrons fill orbitals?

Answer 14

Starting with subshell with the lowest energy

Question 15

What does n+l (aufbau principle) determine?

Answer 15

Energy for all atomic orbitals

Question 16

Describe aufbau principle

Answer 16

How we stick electrons to shell, electrons fill the orbitals from subshell with lowest energy

Question 17

Describe hund’s first rule

Answer 17

Electrons always enter an empty orbital before they pair up

1s filled first, then 2s, 2p, 3s, 3p, 3d etc…

Question 18

What are valence electrons?

Answer 18

Electrons in the outermost shell

Question 19

What are core electrons?

Answer 19

Electrons in the inner shells

Question 20

Does effective charge (Zeff) increase along periods?

Answer 20

Yes

Question 21

What is the covalent radius?

Answer 21

Half the length of a single bond between 2 similar atoms that are covalently bonded

Question 22

Atomic radii in terms of period & group?

Answer 22

Decreases across a period
Increases down a group

Question 23

Describe electronegativity (x)

Answer 23

Tendency of an atom to attract electrons to itself

Question 24

2 things electronegativity is influenced by

Answer 24

1) How far electrons is away from the nucleus
2) How strong does the atom pull

Question 25

3 differences in electronegativity (X)

Answer 25

1) Difference in X less than 0.7- both atoms attract even strength 2) Intermediate differences- clear tendency towards 1 atom but electrons are shared 3) Differences in X more than 1.7- 1 atoms pullls shared electrons away from other, forms ions

Question 26

Feature of electronegativity differences in X less than 0.7

Answer 26

Electrons are shared evenly- covalent bonding

Question 27

Features of electronegativity- intermediate differences

Answer 27

Clear tendency towards an atom but electrons are still shared- polarised bonds

Question 28

Feature of electronegativity in differences in X more than 1.7

Answer 28

1 atom pulls the shared electrons away from each other, forming **ions**

Question 29

What are ionic bonds formed due to?

Answer 29

Due to large differences in electronegativity

Question 30

How do we form molecular obitals (MOs)

Answer 30

Adding or subtracting atomic orbitals from each other

Question 31

3 key determinants for MO formation

Answer 31

1) symmetry 2) Atomic orbital size match 3) Atomic orbital energy match

Question 32

How does orbital size impact interaction?

Answer 32

If their size matches, atomic orbitals will overlap better ## Footnote two 2s orbitals overlap more than one 2s & one 3s orbital

Question 33

How does energy matching impact interaction?

Answer 33

2 atomic orbitals form 1 bonding & 1 anti-bonding moleculr orbital ## Footnote Closer the 2 AO's in energy, stronger their interation is