L2: Atoms, compounds & chemical bonding Flashcards
Structure of an atom
Small, postively charged nucleus surrounded by electrons
What is the nucleus composed of?
Neutrons & protons
What is the atomic number?
Number of protons
What is each electron in an atom described by?
4 quantum numbers
What are the 4 quantum numbers?
1) Principle quantum number n
2) Azimuthal quantum number (L)
3) Magnetic quantum number (ml)
4) Spin magnetic quantum number (ms)
Describe principal quantum number n
Which shell an atom belongs to, distance between electron & nucleus
Describe azimuthal quantum number l
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
Describe magnetic quantum number ml
Number of orbitals and their orientation within a subshell
ml ranges from -l to -l, there are 2l+1 orbitals per subshell
Describe spin magnetic quantum number ms
Orientation of the spin angular momentum of each electron
-1/2 or +1/2
3 different orbitals
s,p,d
What are orbital lobes?
Area where we find a high probability density for locating electrons
What do the different colours on orbital lobes indicate?
2 differnt phases of wavefunction
Probability of nodal planes of locating an electron
0
How does electrons fill orbitals?
Starting with subshell with the lowest energy
What does n+l (aufbau principle) determine?
Energy for all atomic orbitals
Describe aufbau principle
How we stick electrons to shell, electrons fill the orbitals from subshell with lowest energy
Describe hund’s first rule
Electrons always enter an empty orbital before they pair up
1s filled first, then 2s, 2p, 3s, 3p, 3d etc…
What are valence electrons?
Electrons in the outermost shell
What are core electrons?
Electrons in the inner shells
Does effective charge (Zeff) increase along periods?
Yes
What is the covalent radius?
Half the length of a single bond between 2 similar atoms that are covalently bonded
Atomic radii in terms of period & group?
Decreases across a period
Increases down a group
Describe electronegativity (x)
Tendency of an atom to attract electrons to itself
2 things electronegativity is influenced by
1) How far electrons is away from the nucleus
2) How strong does the atom pull
3 differences in electronegativity (X)
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
Feature of electronegativity differences in X less than 0.7
Electrons are shared evenly- covalent bonding
Features of electronegativity- intermediate differences
Clear tendency towards an atom but electrons are still shared- polarised bonds
Feature of electronegativity in differences in X more than 1.7
1 atom pulls the shared electrons away from each other, forming ions
What are ionic bonds formed due to?
Due to large differences in electronegativity
How do we form molecular obitals (MOs)
Adding or subtracting atomic orbitals from each other
3 key determinants for MO formation
1) symmetry
2) Atomic orbital size match
3) Atomic orbital energy match
How does orbital size impact interaction?
If their size matches, atomic orbitals will overlap better
two 2s orbitals overlap more than one 2s & one 3s orbital
How does energy matching impact interaction?
2 atomic orbitals form 1 bonding & 1 anti-bonding moleculr orbital
Closer the 2 AO’s in energy, stronger their interation is
